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Rule2024-30340

Federal Motor Vehicle Safety Standards; Occupant Crash Protection, Seat Belt Reminder Systems, Controls and Displays

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Published

January 3, 2025

Effective

March 4, 2025

Issuing agencies

Transportation DepartmentNational Highway Traffic Safety Administration

Abstract

This document amends Federal Motor Vehicle Safety Standard (FMVSS) No. 208, "Occupant crash protection," to require a seat belt use warning system for rear seats. The rule also updates and enhances the current seat belt warning requirements for the driver's seat belt and extends these requirements to the front outboard passenger seat. The final rule applies (with some exceptions) to passenger cars, trucks, most buses, and multipurpose passenger vehicles with a gross vehicle weight rating of 4,536 kilograms (10,000 pounds) or less. This document also makes related amendments to FMVSS No. 101, "Controls and displays."

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[Federal Register Volume 90, Number 2 (Friday, January 3, 2025)]
[Rules and Regulations]
[Pages 390-468]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-30340]

[[Page 389]]

Vol. 90

Friday,

No. 2

January 3, 2025

Part II

Department of Transportation

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National Highway Traffic Safety Administration

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49 CFR Part 571

Federal Motor Vehicle Safety Standards; Occupant Crash Protection, Seat
Belt Reminder Systems, Controls and Displays; Final Rule

Federal Register / Vol. 90 , No. 2 / Friday, January 3, 2025 / Rules
and Regulations

[[Page 390]]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2024-0071]
RIN 2127-AL37

Federal Motor Vehicle Safety Standards; Occupant Crash
Protection, Seat Belt Reminder Systems, Controls and Displays

AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).

ACTION: Final rule.

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SUMMARY: This document amends Federal Motor Vehicle Safety Standard
(FMVSS) No. 208, ``Occupant crash protection,'' to require a seat belt
use warning system for rear seats. The rule also updates and enhances
the current seat belt warning requirements for the driver's seat belt
and extends these requirements to the front outboard passenger seat.
The final rule applies (with some exceptions) to passenger cars,
trucks, most buses, and multipurpose passenger vehicles with a gross
vehicle weight rating of 4,536 kilograms (10,000 pounds) or less. This
document also makes related amendments to FMVSS No. 101, ``Controls and
displays.''

DATES: Effective date: The effective date of this final rule is March
4, 2025.
Compliance date: The compliance date of this final rule is
September 1, 2026, for the front seat belt warning system requirements
and September 1, 2027, for the rear seat belt warning system
requirements, with optional early compliance permitted. Multi-stage
manufacturers and alterers would have an additional year to comply.
Petitions for reconsideration: Petitions for reconsideration of
this final rule must be received not later than February 18, 2025.

ADDRESSES: Petitions for reconsideration of this final rule must refer
to the docket and notice number set forth above and be submitted to the
Administrator, National Highway Traffic Safety Administration, 1200 New
Jersey Avenue SE, Washington, DC 20590. Note that all petitions
received will be posted without change to <a href="http://www.regulations.gov">www.regulations.gov</a>,
including any personal information provided.
Privacy Act: Petitions will be placed in the docket. Anyone is able
to search the electronic form of all documents received into any of our
dockets by the name of the individual submitting the comment (or
signing the comment, if submitted on behalf of an association,
business, labor union, etc.). You may review DOT's complete Privacy Act
Statement in the Federal Register published on April 11, 2000 (Volume
65, Number 70; Pages 19477-78) or you may visit <a href="https://www.transportation.gov/individuals/privacy/privacy-act-system-records-notices">https://www.transportation.gov/individuals/privacy/privacy-act-system-records-notices</a>.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact
Ms. Carla Rush, Office of Crashworthiness Standards, Telephone: (202)
366-4583; Email: <a href="/cdn-cgi/l/email-protection#7516140719145b0700061d35111a015b121a03">[email&#160;protected]</a>; Facsimile: (202) 493-2739. For
legal issues, you may contact Mr. John Piazza (<a href="/cdn-cgi/l/email-protection#713b1e191f5f2118100b0b1031151e055f161e07">[email&#160;protected]</a>) or
Eli Wachtel (<a href="/cdn-cgi/l/email-protection#83c6efeaadd4e2e0ebf7e6efc3e7ecf7ade4ecf5">[email&#160;protected]</a>), Office of Chief Counsel, Telephone:
(202) 366-2992; Facsimile: (202) 366-3820. The address of these
officials is: the National Highway Traffic Safety Administration, 1200
New Jersey Avenue SE, Washington, DC, 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
III. Other Seat Belt Reminder Requirements and Protocols
IV. Statutory Authority
V. Summary of the NPRM
VI. Final Rule and Response to Comments
A. Rear Seat Belt Warning Requirements
1. Applicability
2. Requirements
a. Visual Warning on Vehicle Start-Up
i. Type of Information Conveyed by the Visual Warning and
Whether Occupant Detection Should Be Required
ii. Lack of an Audible Warning
iii. Triggering Conditions for Start-of-Trip Warning (Not
Including Occupant Detection Criteria)
iv. Seat Occupancy Criteria and Interaction With Child Restraint
Systems
v. Duration
vi. Other Aspects
b. Audio-Visual Change-of-Status Warning
c. Electrical Connections/Removable Seats
d. Owner's Manual Instructions
e. Telltale Location
3. Alternative Warning Signals
B. Front Seat Belt Warning Requirements
1. Applicability
2. Driver's Seat Belt Warning for Light Buses
3. Visual and Audible Warning Duration and Activation
4. Visibility of Visual Warning for Front Outboard Passenger
Seat Belt
5. Front Seat Occupant Detection and Seat Occupancy Criteria
C. Issues Common to the Front and Rear Seat Belt Warning
Requirements
1. Modification of Start-of-Trip Warning Trigger Related
Ignition Switch Position To Accommodate EVs
2. Belt Use Criteria
3. Visual Warning Characteristics
4. Interaction With Other Vehicle Warnings
5. Audible Warning Characteristics (Other Than Duration)
6. Warning Deactivation and Acknowledgement and Hardening
7. Vehicles With Automated Driving Systems
8. Test Procedures
VII. Regulatory Alternatives
VIII. Overview of Benefits and Costs
A. Final Rule Requirements
1. Rear Seat Belt Warning System
2. Front Seat Belt Warning System
3. Overall Benefits and Costs of the Final Rule
B. Regulatory Alternatives
1. Occupant Detection in Rear Seats
2. 90-Second Front Outboard Seat Belt Warning
3. Seat Belt Warning for Front Center Seat
IX. Compliance Dates
X. Regulatory Analyses
Appendix A. List of Comments Cited in Preamble

I. Executive Summary

This final rule amends Federal Motor Vehicle Safety Standard (FMVSS
or Standard) No. 208, ``Occupant crash protection,'' to require a seat
belt use warning system for rear seats. This rule completes NHTSA's
response to a mandate in the Moving Ahead for Progress in the 21st
Century Act (MAP-21) that directed NHTSA to initiate a rulemaking to
require a seat belt warning for the rear seats in motor vehicles; it
also completes NHTSA's action on a rulemaking petition from Public
Citizen and Advocates for Highway and Auto Safety for the same rule.
The final rule also updates and enhances the current seat belt warning
requirements for the driver's seat belt and extends these requirements
to the front outboard passenger seat. The final rule applies (with some
exceptions) to passenger cars, trucks, most buses, and multipurpose
passenger vehicles (MPVs) with a gross vehicle weight rating (GVWR) of
4,536 kilograms (10,000 pounds) or less. NHTSA is issuing this final
rule under the National Traffic and Motor Vehicle Safety Act (Safety
Act), 49 U.S.C. chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 et
seq.).

Safety Need for the Final Rule

Using a seat belt is one of the most effective ways a motor vehicle
occupant can prevent death and injury in a crash. Seat belts prevent
occupants from being ejected from the vehicle, provide ``ride-down'' by
gradually decelerating the occupant as the vehicle deforms and absorbs
energy, and reduce occupant contact with harmful interior surfaces and
other occupants. Seat belts are effective in most types of crashes and

[[Page 391]]

greatly reduce the risk of fatal and non-fatal injuries compared to the
risk faced by unrestrained occupants.
While seat belt use is meaningfully higher than it was a decade
ago, there is room for improvement. Usage rates for seat belts in rear
seats have consistently been below those for the front seats; and while
front seat belt use rates increased in the early 2010s, for the last
several years they have plateaued. According to data from NHTSA's
annual study of observed seat belt use, in every year from 2013 through
2022, seat belt use was lower in the rear seats than in the front
seats, ranging from a difference of about 9 percentage points in 2013
(78 percent vs. 87 percent) to about 14 percentage points in 2017 (75
percent vs. 89 percent). In 2022, front seat belt use was about 91.6
percent and rear seat belt use was about 81.7 percent.
Every year, thousands of unrestrained motor vehicle occupants are
killed in crashes and tens of thousands of unrestrained occupants are
injured (additional details on the target population are provided in
the summary of benefits and costs later in this executive summary).
Seat belt warning systems (also referred to as seat belt reminder
systems) encourage seat belt use by reminding unbuckled occupants to
fasten their belts and/or by informing the driver that a passenger is
unbelted so that the driver can request the unbelted occupant to buckle
up. The warnings provided by seat belt warning systems typically
consist of visual and/or audible signals. Research by NHTSA and others
shows that seat belt warning systems are effective at getting unbuckled
occupants to fasten their seat belts.
FMVSS No. 208 currently requires a short-duration audio-visual seat
belt warning for the driver's seat belt in passenger cars, most trucks
and MPVs with a GVWR of 4,536 kg (10,000 lb) or less, and buses with a
GVWR of 3,855 kg (8,500 lb) or less. Under these current requirements,
the visual component of the warning generally must be at least 60
seconds long, and the audible component must be at least four seconds
long.
Voluntary adoption by vehicle manufacturers of warnings that go
beyond this regulatory minimum, while considerable, has been mixed.
Although the regulations do not require seat belt warnings for any
seating position other than the driver's seat, almost all model year
(MY) 2022 vehicles have a voluntarily provided seat belt warning for
the front outboard passenger seat. However, voluntary adoption for rear
seats has been much slower, as only about 47 percent of MY 2022
vehicles come equipped with a voluntarily provided rear seat belt
warning system. Most vehicles already provide a seat belt warning for
both front outboard seats that is much longer than the minimal required
warning for the driver's seat belt, with the vast majority of vehicles
including an alert that is at least 90 seconds. This widespread
adoption suggests that the front seat belt warning minimum requirements
in the FMVSS are outdated, as consumers accept audio-visual reminders
that are far longer than the required minimums.
As discussed above, rear seat belt use rates have persistently been
below those for the front seats, and progress on front seat belt use
rates has slowed. Moreover, unbuckled occupants, in the front and rear
seats, continue to be overrepresented in fatal crashes (51 percent),
given the lower exposure of unbelted occupants relative to belted
occupants (because front seat belt use is about 90 percent and rear
seat belt use is 80 percent). Despite the effectiveness of seat belts
and seat belt warnings, most new vehicles continue to lack a rear seat
belt warning. Additionally, while most vehicles provide some level of
enhanced reminders for the front seats, this level of enhanced
protection has not occurred for all vehicles and is not standardized.
This gap in protection suggests a need for a beneficial safety
technology that is not being met in the vehicle market. This final rule
is intended to meet this safety need.

Legal Authority and Prior Regulatory History

NHTSA is issuing this final rule pursuant to the National Traffic
and Motor Vehicle Safety Act (49 U.S.C. 30101 et seq.) (Safety Act),
which authorizes NHTSA to establish FMVSSs. That statute requires
safety standards to be objective, practicable, and meet the need for
safety, among other things. NHTSA has concluded that the finalized
requirements satisfy these statutory criteria.
This final rule completes NHTSA's response to a rulemaking mandate
in MAP-21. MAP-21 required DOT (NHTSA, by delegation) to initiate a
rulemaking proceeding to require rear seat belt warnings and directed
the agency to issue a final rule unless the rule would not meet the
Safety Act requirements for an FMVSS.
This final rule also completes NHTSA's action on a rulemaking
petition from Public Citizen and Advocates for Highway and Auto Safety.
The petition requested that NHTSA issue a rule requiring a seat belt
warning system for rear seats on passenger cars and MPVs with a GVWR of
4,536 kg (10,000 lb) or less.

Summary of the Final Rule

This final rule amends the existing seat belt warning provisions in
FMVSS No. 208. The final rule has two main components. The first
requires a seat belt warning for the rear seats. The second amends and
enhances the seat belt warning requirements for the front outboard
seats. The requirements apply (with some exceptions) to passenger cars
and trucks, most buses, and multipurpose passenger vehicles with a GVWR
of 4,536 kg (10,000 lb) or less.
1. Rear Seat Belt Reminder Requirements
The first component of this final rule is a set of requirements for
a seat belt warning for rear seats. The new requirements have four main
elements.
<bullet> Visual warning on vehicle start-up to inform the driver of
the status of the rear seat belts. The final rule requires a visual
warning that informs the driver how many or which rear seat belts are
in use and/or not in use. The warning must activate when the ignition
(or, for electric vehicles (EVs), propulsion system) is activated, and
last for at least 60 seconds. No visual warning is required if the
system can determine that there are no occupied rear seats or if there
are no occupied rear seats with a seat belt that is not in use.
<bullet> Audio-visual change-of-status warning. The final rule
requires an audio-visual warning whenever a fastened rear seat belt is
unfastened while the vehicle is in forward or reverse drive mode. (The
warning is not required if the system can determine that a rear
passenger has unfastened the seat belt in order to exit the vehicle or
switch seats.) The warning must last for at least 30 seconds or until
the seat belt that triggered the warning is re-fastened. The audible
portion of the warning may be temporarily paused to allow another
audible safety warning alerting the driver to take immediate action.
<bullet> Requirements related to electrical connections. Readily
removable rear seats must either automatically establish the electrical
connections when the seat is put in place or, if a manual connection is
required, the connectors must be readily accessible. Vehicles equipped
with certain types of seat belt warning systems are additionally
required to provide a visual warning to the driver if a proper
electrical connection has not been established.
<bullet> Owner's manual requirements. The vehicle owner's manual
(which includes information provided by the vehicle manufacturer to the
consumer, whether

[[Page 392]]

in digital or printed form) must describe the warning system's
features, including the location and format of the visual warnings. It
must also include instructions on how to make any manual electrical
connections for readily removable seats.
2. Front Outboard Seat Belt Warning Requirements
The final rule includes several changes and enhancements to the
seat belt warning requirements for the front outboard seats. The new
requirements have two main elements.
<bullet> Seat belt warning now required for front outboard
passenger seat. This final rule requires a seat belt warning for the
front outboard passenger seat. It does not require one for front center
seats because, among other things, doing so would not be cost-
effective. Currently, only the driver's seat is required to have a seat
belt warning, although almost all vehicles now provide a seat belt
warning for the front outboard passenger seat as well.
<bullet> Enhanced audio-visual seat belt warning. The final rule
requires a longer-duration audio-visual warning than is currently
required for the driver's seat belt. The final requirements for this
warning differ from the proposal, which would have required (with some
exceptions) an audio-visual warning lasting until the belt at any
occupied front outboard seat was fastened. This included a warning at
the start of a trip and if a belt was unfastened during a trip. The
proposal did not include any other warning triggers, such as vehicle
speed. The final rule requires a visual warning and a two-phase audible
warning that is based, in part, on vehicle speed.
Visual warning. Under the final rule, a visual warning is required
whenever the ignition switch is in the ``on'' or ``start'' position (or
the propulsion system is activated), the seat is occupied, and the seat
belt is not in use. The warning must be visible to the driver.
Audible warning. The final rule requires a two-phase audible
warning. The first phase warning must activate when the ignition/
propulsion system is activated, the seat is occupied, and the belt is
not in use. The first phase warning must last for at least 30 seconds,
unless the seat belt that triggered the warning is fastened or the
second phase audible warning is activated within that time. The second
phase audible warning must activate, and remain active, whenever the
seat is occupied, the seat belt is not in use, and the vehicle speed is
at least 10 km/h (6.2 mph). The audible warning may be temporarily
paused to allow another audible safety warning alerting the driver to
take immediate action.
The final rule also contains requirements for the visual and
audible warnings as well as for other system features.

Compliance Date

This final rule establishes a compliance date for the amendments to
FMVSS No. 208, ``Occupant crash protection,'' as follows. Manufacturers
must comply with the amendments as of September 1, 2026 for the front
seat belt warning system requirements and September 1, 2027 for the
rear seat belt warning system requirements, with optional early
compliance (see Section IX for details). Consistent with 49 CFR
571.8(b), multi-stage manufacturers and alterers have an additional
year to comply.

Regulatory Alternatives

NHTSA considered a wide range of alternatives to the proposed
requirements. The main alternatives NHTSA considered were the seat belt
warning requirements in Economic Commission for Europe (ECE) Regulation
No. 16 (R16) and Euro New Car Assessment Programme (Euro NCAP). The
finalized requirements are identical or similar to ECE R16 and Euro
NCAP in many respects but differ from them in several ways. For
instance, while under ECE R16 the smallest occupant a rear seat belt
system with occupant detection must be capable of detecting is a small-
statured adult female, under the final rule such systems must be
capable of detecting occupants as small as a 6-year-old child and
activating the warning accordingly. Another way the proposal differs
from ECE R16 is the duration of the front seat belt warning on vehicle
start-up: R16 generally requires only a 30-60 second audio-visual
warning; the final rule requires, under certain conditions, an audio-
visual warning that lasts until the seat belt is buckled. The final
regulatory analysis quantifies the costs and benefits of three specific
regulatory alternatives: requiring occupant detection for the rear seat
belt warning system; requiring (for the front outboard seats) an audio-
visual warning on vehicle start-up with a duration of 90 seconds; and
requiring a seat belt warning for front center seats.

Benefits and Costs of the Proposed Requirements

This final rule is significant and was reviewed by the Office of
Management and Budget under Executive Order 12866, as amended by
Executive Order 14094.
NHTSA estimates the target population and the benefits and costs of
the final rule requirements in the stand-alone final regulatory impact
analysis (FRIA) that is being placed in the docket with this final rule
and is summarized in this document.
Based on NHTSA's data on fatalities and injuries from motor vehicle
crashes, adjusted to account for the benefits of other mandatory safety
technologies, there are, on average, 822 fatalities and 11,409 injuries
to unrestrained rear seat occupants and 8,383 fatalities and 154,739
injuries to unrestrained front outboard seat occupants each year. The
final rule requirements are aimed at reducing these deaths and
injuries.
NHTSA estimates the benefits it expects from the final rule seat
belt warning requirements. The benefits are the fatalities and injuries
that would be prevented by these requirements. The benefits depend,
principally, on the expected increase in seat belt use and the
effectiveness of seat belts in preventing deaths and injuries.
For the rear seat belt warning system analysis, NHTSA used a
``low'' and a ``high'' estimate for the increase in rear belt use with
the warning system. For occupants 11 years and older, these were 3 and
5 percentage points, respectively, and for occupants from 6 to 10 years
old, 0.3 and 0.4 percentage points respectively.\1\ For simplicity,
NHTSA refers to these scenarios as ``Low'' and ``High.'' The estimated
annual benefits for rear seat belt warning systems are presented in
table 1.\2\
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\1\ Children in booster seats are part of the target population
for this final rule because they should be restrained with the seat
belt and so would benefit from a seat belt reminder. The transition
to a booster seat typically occurs from ages 4-7 years, and
recommendations to remain in a booster seat exist until age 12
years.https://<a href="http://www.nhtsa.gov/vehicle-safety/car-seats-and-booster-seats#find-the-right-car-seat-car-seat-recommendations">www.nhtsa.gov/vehicle-safety/car-seats-and-booster-seats#find-the-right-car-seat-car-seat-recommendations</a>.
\2\ The Abbreviated Injury Scale (AIS) is a classification
system for assessing impact injury severity developed and published
by the Association for the Advancement of Automotive Medicine and is
used for coding single injuries, assessing multiple injuries, or for
assessing cumulative effects of more than one injury. MAIS
represents the maximum injury severity of an occupant at an AIS
level, i.e., the highest single AIS for a person with one or more
injuries. MAIS 1 & 2 injuries are considered minor injuries and MAIS
3-5 are considered serious injuries.

[[Page 393]]

Table 1--Estimated Annual Benefits--Potential Lives Saved and Injuries
Prevented for Rear Seat Belt Warning Systems (SBWS) Without Occupant
Detection, With Estimated ``Low'' and ``High'' Percentage Point Increase
in Belt Use
------------------------------------------------------------------------
Injury level Low High
------------------------------------------------------------------------
MAIS 1.................................. 36 54
MAIS 2.................................. 80 120
MAIS 3.................................. 26 38
MAIS 4.................................. 4 6
MAIS 5.................................. 1 2
-------------------------------
Total Injuries...................... 148 221
------------------------------------------------------------------------
Fatal................................... 26 39
------------------------------------------------------------------------

Another way to measure benefits is by calculating equivalent lives
saved (ELS). Equivalent lives saved are the number of prevented
fatalities added to the number of prevented injuries, with the
prevented injuries expressed in terms of fatalities (that is, with an
injury expressed as a fraction of a fatality, so that the more serious
the injury, the higher the fraction). The estimated equivalent lives
saved assuming either a 3 percent or 7 percent discount rate are
presented in table 2.

Table 2--Estimated Annual Benefits--Equivalent Lives Saved (ELS)--Rear
SBWS Without Occupant Detection
------------------------------------------------------------------------
3 Percent 7 Percent
Belt use increase discount rate discount rate
------------------------------------------------------------------------
Low................................... 29.98 24.31
High.................................. 45.09 36.55
------------------------------------------------------------------------

NHTSA also estimates the costs of the final rule requirements for
rear seat belt warnings. NHTSA estimates that the minimum cost to
comply with the rear seat belt warning requirements is $166.44 million
(M). This is based on a per-vehicle cost of $19.59 for 53.1 percent of
16M affected new vehicles.
Based on the foregoing, NHTSA performed benefit-cost and cost-
effectiveness analyses. A benefit-cost analysis calculates the net
benefits, which is the difference between the benefits flowing from
injury and fatality reductions and the cost of the rule. The net
benefit estimates are presented in table 3. The cost-effectiveness
analysis derives the cost per equivalent life saved, which is equal to
the total cost of the rule divided by the total fatal equivalents that
it prevents. These estimates are presented in table 4.

Table 3--Net Benefits--Rear SBWS Without Occupant Detection
[2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
Benefits 3 Benefits 7 Net benefits 3 Net benefits 7
Belt use increase percent percent Cost percent percent
discount discount discount rate discount rate
----------------------------------------------------------------------------------------------------------------
Low................................ $357.78 $290.05 $166.4 $191.34 $123.62
High............................... 538.00 436.16 166.4 371.56 269.72
----------------------------------------------------------------------------------------------------------------

Table 4--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--Rear SBWS Without Occupant Detection
[2020 Dollars, in Millions]
----------------------------------------------------------------------------------------------------------------
ELS 3 ELS 7 Cost/ELS 3 Cost/ELS 7
Belt use increase percent percent Cost percent percent
discount discount discount discount
----------------------------------------------------------------------------------------------------------------
Low...................................... 29.98 24.31 $166.4 $5.55 $6.85
High..................................... 45.09 36.55 166.4 3.69 4.55
----------------------------------------------------------------------------------------------------------------

This final rule also enhances the driver seat belt warning
requirements by requiring an indefinite visual warning and a two-phase
audible warning that is based, in part, on vehicle speed that remains
active until the driver's seat belt is buckled and extending these
enhanced driver's seat belt warning requirements to the front outboard
passenger seat. NHTSA estimates the annual benefits of a seat belt
warning for the driver and outboard front passenger that remains active
until the occupant's seat belt is buckled as shown in table 5 and table
6.

[[Page 394]]

Table 5--Estimated Annual Benefits--Lives Saved and Injuries Prevented--Indefinite Duration SBWS (Front Outboard
Seats)
----------------------------------------------------------------------------------------------------------------
Front
Injury level Driver passenger Total
----------------------------------------------------------------------------------------------------------------
MAIS 1.......................................................... 129 14 143
MAIS 2.......................................................... 151 19 170
MAIS 3.......................................................... 62 8 69
MAIS 4.......................................................... 9 1 10
MAIS 5.......................................................... 3 0 3
-----------------------------------------------
Total Injuries.............................................. 354 42 395
----------------------------------------------------------------------------------------------------------------
Fatal........................................................... 20 2 22
----------------------------------------------------------------------------------------------------------------

Table 6--Estimated Annual Benefits--Equivalent Lives Saved--Indefinite Duration SBWS (Front Outboard Seats)
----------------------------------------------------------------------------------------------------------------
3 Percent 7 Percent
Undiscounted discount rate discount rate
----------------------------------------------------------------------------------------------------------------
Driver........................................................ 42.26 34.98 28.36
Front Passenger............................................... 4.44 3.68 2.99
-------------------------------------------------
Total..................................................... 46.70 38.66 31.35
----------------------------------------------------------------------------------------------------------------

NHTSA estimates that the incremental cost of the enhanced seat belt
warning for the driver's seat and the front outboard passenger seat
would be no greater than the currently available seat belt warning.
Although a seat belt warning is currently not required for the front
outboard passenger seats, we estimate that 96 percent of new vehicles
are equipped with them.\3\ NHTSA estimates that the cost for equipping
a front outboard passenger seat with a seat belt warning system is
about $2.13 per vehicle. To equip a seat belt warning system in the
front outboard passenger seat positions on the remaining four percent
of the new vehicle fleet (16 million) without such a warning is $1.36
million (= $2.13 x 0.04 x 16 million).
---------------------------------------------------------------------------

\3\ Based on data on total projected vehicle sales in the United
States for MY 2022 from the agency's New Car Assessment Program
Purchasing with Safety in Mind: What to Look For When Buying a
Vehicle program.
---------------------------------------------------------------------------

The total monetized benefits, costs, and net benefits (total
monetized benefits--total cost) of the enhanced seat belt warning
system for the driver and front passenger are shown in table 7. Table 8
presents the results of the cost effectiveness analysis--cost per
equivalent lives saved from enhanced SBWS for the driver and front
outboard passenger.

Table 7--Annual Monetized Benefits, Costs, and Net Benefits--Indefinite SBWS (Front Outboard Seats)
[2020 Dollars, in Millions]
----------------------------------------------------------------------------------------------------------------
Driver Front passenger Driver and front
---------------------------------------------------- passenger
-------------------------
3 Percent 7 Percent 3 Percent 7 Percent 3 Percent 7 Percent
----------------------------------------------------------------------------------------------------------------
Passenger Car Benefits............ $188.89 $154.12 $22.86 $18.65 $211.75 $172.77
Light Truck & Van Benefits........ 228.51 184.29 21.05 16.97 249.56 201.26
-----------------------------------------------------------------------------
Total Benefits................ 417.41 338.41 43.90 35.62 461.31 374.03
Total Costs................... 0 0 1.36 1.36 1.36 1.36
----------------------------------------------------------------------------------------------------------------
Net Benefits...................... 417.41 338.41 42.54 34.26 459.95 372.67
----------------------------------------------------------------------------------------------------------------

Table 8--Cost-Effectiveness Analysis (Cost per Equivalent Life Saved)--Indefinite SBWS (Front Outboard Seats)
[2020 Dollars, in millions]
----------------------------------------------------------------------------------------------------------------
Discount rate ELS Cost Cost/ELS
----------------------------------------------------------------------------------------------------------------
3 percent....................................................... 38.66 $1.36 $0.04
7 percent....................................................... 31.35 1.36 0.04
----------------------------------------------------------------------------------------------------------------

The net benefits of the final rule requiring seat belt warning for
rear seating positions and the enhanced seat belt warning for the front
outboard seats are shown in table 9. The net benefits are positive for
both 3 percent and 7

[[Page 395]]

percent discount rates and for both the low and high effectiveness
estimates for rear seat SBWS.

Table 9--Net Benefits From the Final Rule (SBWS Without Occupant
Detection for Rear Seating Positions and Indefinite SBWS for Front
Outboard Seating Positions)
[2020 Dollars, in millions]
------------------------------------------------------------------------
3 Percent 7 Percent
discount rate discount rate
------------------------------------------------------------------------
Front Outboard Seats.................... $459.95 $372.67
Rear Seats (low increase in rear seat 191.34 123.62
belt use)..............................
Rear Seats (high increase in rear seat 371.56 269.72
belt use)..............................
-------------------------------
Total Net Benefits (low increase in 651.29 496.28
rear belt use).....................
Total Net Benefits (high increase in 831.51 642.39
rear belt use).....................
------------------------------------------------------------------------

II. Background

On September 7, 2023, NHTSA published a notice of proposed
rulemaking (NPRM) to amend FMVSS No. 208, ``Occupant crash
protection,'' to require a seat belt use warning system for rear seats
and to enhance the existing front seat belt warning requirements,
including requiring a seat belt warning for the front outboard
passenger seat and increasing the duration of the warning.\4\ This
section provides an abbreviated background on the subject matter and
regulatory history of the proposed requirements. For a fuller
discussion, the reader is referred to the NPRM.\5\
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\4\ 88 FR 61674.
\5\ Id. at pgs. 61680-61686.
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Seat Belts and Seat Belt Warning Systems
Using a seat belt is one of the most effective actions a motor
vehicle occupant can take to prevent death and injury in a crash.\6\
Seat belts protect occupants in various ways. They prevent occupants
from being ejected from the vehicle, gradually decelerate the occupant
as the vehicle deforms and absorbs energy, and reduce the occurrence of
occupant contact with harmful interior surfaces and other occupants.\7\
Research has found that seat belts greatly reduce the risk of fatal and
non-fatal injuries compared to the risk faced by unrestrained
occupants. For rear seat occupants, seat belts reduce the risk of
fatality by 55 percent (for passenger cars) and 74 percent (for light
trucks and vans). For drivers, seat belts reduce the risk of fatality
by 48 percent (for passenger cars) and 61 percent (for light trucks and
vans) and reduce the risk of moderate to greater severity injuries by
65 percent. For front outboard passengers, seat belts reduce the risk
of fatality by 37 percent (for passenger cars) and by 58 percent (for
light trucks and vans) and reduce the risk of moderate to greater
severity injuries by 65 percent.\8\
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\6\ See, e.g., 68 FR 46262 (Aug. 5, 2003). See also Buckling Up:
Technologies to Increase Seat Belt Use. Special Report 278 at 18,
Committee for the Safety Belt Technology Study, Transportation
Research Board of The National Academies (2003).
\7\ Charles J. Kahane, Lives Saved by Vehicle Safety
Technologies and Associated Federal Motor Vehicle Safety Standards,
1960 to 2012--Passenger Cars and LTVs--With Reviews of 26 FMVSS and
the Effectiveness of Their Associated Safety Technologies in
Reducing Fatalities, Injuries, and Crashes. 89 DOT HS 812 069 at 89,
Department of Transportation, National Highway Traffic Safety
Administration (2015).
\8\ See the Final Regulatory Impact Analysis (FRIA) (in the
docket for this rulemaking) for these effectiveness estimates.
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While seat belt use is meaningfully higher than it was a decade
ago, there is room for improvement. Usage rates for rear seat belts
have consistently been below those for the front seats, and while front
seat belt use rates increased early in the previous decade, for the
last several years they have plateaued. According to data from NHTSA's
National Occupant Protection Use Survey (NOPUS), from 2013 to 2022,
seat belt use was lower in the rear seat than in the front seat,
ranging from a difference of 8.8 percentage points in 2013 (78.3
percent vs. 87.1 percent) to 14.3 percentage points in 2017 (75.4
percent vs. 89.7 percent).\9\ In 2022, front seat belt use was 91.6
percent and rear seat belt use was 81.7 percent.\10\ See Figure 1.
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\9\ Boyle, L.L. (2022, August). Occupant restraint use in 2021:
Results from the NOPUS Controlled Intersection Study (Report No. DOT
HS 813 344). National Highway Traffic Safety Administration. NOPUS
is the only nationwide probability-based observational survey of
seat belt use in the United States. The survey observes seat belt
use as it actually occurs at randomly-selected roadway sites, and
involves a large number of occupants (68,804 in 2021). NOPUS
observations are made during daylight hours and are not necessarily
representative of high-risk driving times when belt use may be
lower.
\10\ Boyle, L.L. (2023, November). Occupant restraint use in
2022: Results from the NOPUS Controlled Intersection Study (Report
No. DOT HS 813 523). National Highway Traffic Safety Administration.

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[[Page 396]]

[GRAPHIC] [TIFF OMITTED] TR03JA25.000

NHTSA has, over time, implemented a variety of strategies to
increase seat belt use. These have included sponsoring national media
campaigns, supporting the enactment of state seat belt use laws and
high-visibility enforcement, and facilitating or requiring vehicle-
based strategies.\11\ While such measures have helped make enormous
progress, the persistent gaps in seat belt use suggest that additional
approaches may be necessary.
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\11\ For example, NHTSA runs a Congressionally mandated High
Visibility Enforcement annual campaign focused on increasing seat
belt use. The Click It or Ticket nationwide campaign has been in
effect for about 20 years. It runs every year from mid-May through
the Memorial Day weekend, into the first week in June.
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Seat belt warning systems (also referred to as seat belt reminder
systems) are a vehicle-based strategy to increase belt use. Seat belt
warning systems encourage seat belt use by reminding unbuckled
occupants to fasten their belts and/or by informing the driver that a
passenger is unbelted, so that the driver can request the unbelted
occupant buckle up. The warnings provided by seat belt warning systems
typically consist of visual and audible signals. An optimized warning
system balances effectiveness and annoyance, so that the warning is
noticeable enough that the occupants will be motivated to fasten their
belts, but not so intrusive that an occupant may attempt to circumvent
or disable it or the public will not accept it. Research by NHTSA and
others shows that seat belt warning systems are effective at getting
unbuckled occupants to fasten their seat belts. (We take a closer look
at this research in Section VIII, Overview of Benefits and Costs, and
the FRIA.) \12\
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\12\ See also Section V of the NPRM (pgs. 61684-61685).
---------------------------------------------------------------------------

FMVSS No. 208 currently requires a short audio-visual seat belt
warning for the driver's seat belt on passenger cars; \13\ trucks and
MPVs with a GVWR of 4,536 kg (10,000 lb) or less (except for some
compliance options which do not require the warning); \14\ and buses
with a GVWR of 3,855 kg (8,500 lb) or less and an unloaded weight less
than or equal to 2,495 kg (5,500 lb).\15\ The standard does not require
seat belt warnings for any seating position other than the driver's
seat.\16\
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\13\ S4.1.5.1(a)(3); S7.3.
\14\ S4.2.6; S7.3.
\15\ S4.2.6 (with the exception of some compliance options).
\16\ See, e.g., Interpretation Letter from NHTSA to R. Lucki,
July 24, 1985 (``Thus, the intent was to require a warning system
for only the driver's position.''). All NHTSA interpretation letters
cited in this preamble are available at <a href="https://www.nhtsa.gov/nhtsa-interpretation-file-search">https://www.nhtsa.gov/nhtsa-interpretation-file-search</a>.
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Manufacturers have two compliance options for the driver's
warning.\17\ The first option requires that if the key is in the ``on''
or ``start'' position and the seat belt is not in use, the vehicle must
provide a visual warning for at least 60 seconds, and an audible
warning that lasts 4 to 8 seconds. Under the second option, when the
key is turned to the ``on'' or ``start'' position, the vehicle must
provide a visual warning for 4 to 8 seconds (regardless of whether the
driver seat belt is fastened) and an audible warning lasting 4 to 8
seconds if the driver seat belt is not in use.\18\ The current seat
belt warning requirements (i.e., for the driver's seat only) have been
in the standard since 1974.\19\
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\17\ 49 CFR 571.208, S7.3.
\18\ The warning requirements for automatic belts in S4.5.3
mirror, with some differences, the first compliance option.
Automatic belts are rarely, if ever, installed in current production
vehicles, and NHTSA's regulations limit the seating positions for
which automatic belts may be used to rear seats.
\19\ 39 FR 42692 (Dec. 6, 1974).
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Although not required by NHTSA's regulations, most currently
produced vehicles have a seat belt warning for the front outboard
passenger seat. Based on data on total projected vehicle sales in the
United States for MY 2022 from the agency's New Car Assessment Program
(NCAP) Purchasing with Safety in Mind: What to Look For When Buying a
Vehicle program, almost all (about 97 percent) MY 2022 vehicles offered
for sale in the United States were equipped with a seat belt warning
for the front outboard passenger seat.\20\ Further, almost all vehicles
already provide an audio-visual seat belt warning for both front
outboard seats that is longer than the minimum warning for the driver's
seat belt currently required in FMVSS No. 208. However, the persistence
of the front seat belt warning, while often greater than the minimal
durations required by FMVSS No. 208, is not consistent across new
vehicles. Specifically, a little over half of MY 2022 vehicles provide
a visual warning that lasts until the belts at any occupied front
outboard seat are fastened, and almost all (about 93 percent) have an
audible warning lasting at least a minute and a half; however, less
than half have an audible warning lasting at least two minutes.\21\
This means that while many new vehicles have significantly enhanced
reminders, many do not. This disparity, along with the plateauing front
seat belt use numbers, suggests that the current regulatory minima are

[[Page 397]]

too short, and that in the absence of a requirement, persistent audible
reminders that could improve front seat belt use are not widely
available in the market.22 23 24
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\20\ Through the NCAP program, NHTSA sends annual requests for
safety information about new vehicles to vehicle manufacturers. This
includes specific questions on seat belt reminder systems. The focus
of this request for information is for vehicle models that will be
sold in the upcoming model year that have a GVWR of 4,536 kg (10,000
lb) or less, and this data generally covers all such vehicles
offered for sale in the U.S. for MY 2022. Throughout this document
we will refer to this data as our ``NCAP data'' or ``Purchasing with
Safety in Mind: What to Look For When Buying a Vehicle'' data or
information.
\21\ See NPRM, pgs. 61709-61711, and appendix A.
\22\ Mark Freedman et al. The Effectiveness of Enhanced Seat
Belt Reminder Systems Draft Report: Observational Field Data
Collection Methodology and Findings. 2007. DOT HS-810-844.
Washington, DC: National Highway Traffic Safety Administration.
\23\ N. Lerner et al. 2007. Acceptability and Potential
Effectiveness of Enhanced Seat Belt Reminder System Features. DOT HS
810 848. Washington, DC: National Highway Traffic Safety
Administration [hereinafter DOT 2007.
\24\ Transportation Research Board Study at 8, 25; Mark Freedman
et al., Effectiveness and Acceptance of Enhanced Seat Belt Reminder
Systems: Characteristics of Optimal Reminder Systems Final Report.
DOT HS 811 097.
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While almost all MY 2022 vehicles have a seat belt warning for the
front outboard passenger seat, under half come equipped with a rear
seat belt warning system. Rear seat belt warnings were first introduced
in the United States by Volvo around 2009. About 47 percent of MY 2022
vehicles, from 15 vehicle manufacturers, are equipped with a rear seat
belt warning system. Thus, while rear seat belt warnings have become
more widely deployed in recent years, the majority of the current fleet
still is not equipped with them.
In short, front seat belt use rates appear to have plateaued, and
rear seat belt use rates have persistently been below those for the
front seats. Moreover, unbuckled occupants continue to be
overrepresented in fatal crashes (51 percent), given the lower exposure
of unbelted occupants relative to belted occupants (because front seat
belt use was about 90 percent and rear seat belt use was 80 percent for
the period in question). In spite of the effectiveness of seat belts
and seat belt warnings, most new vehicles continue to lack a rear seat
belt warning, and, while many vehicles provide significantly enhanced
reminders for the front seats, many do not. This suggests a need for a
beneficial safety technology that is not being met in the vehicle
market. This final rule is intended to meet that need.
Rulemaking Petition, MAP-21 Mandate, and Prior Rulemaking Notices for
This Action
On November 21, 2007, Public Citizen and Advocates for Highway and
Auto Safety (Advocates, and, collectively, petitioners) petitioned
NHTSA to amend FMVSS No. 208 to require a seat belt warning system for
rear seats on passenger cars and MPVs with a GVWR of 4,536 kg (10,000
lb) or less.\25\ On June 29, 2010, the agency published a Request for
Comments document (RFC) on the petition.\26\ The RFC discussed the
agency's research and findings regarding rear seat belt warnings and
solicited comments. NHTSA subsequently granted the petition.
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\25\ Docket No. NHTSA-2010-0061-0002.
\26\ 75 FR 37343 (June 29, 2010) (Docket No. NHTSA-2010-0061).
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In 2012, Congress passed the Moving Ahead for Progress in the 21st
Century Act (MAP-21).\27\ That legislation contained two provisions
regarding seat belt warning systems. First, it repealed the 8-second
durational limit for the driver's seat belt audible warning.\28\
Second, it required the Secretary of Transportation to initiate a
rulemaking proceeding to amend FMVSS No. 208 to provide a safety belt
use warning system for designated seating positions in the rear
seat.\29\ It directed the Secretary to either issue a final rule, or,
if the Secretary determines that such an amendment does not meet the
requirements and considerations of 49 U.S.C. 30111,\30\ to submit a
report to Congress describing the reasons for not prescribing such a
standard.
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\27\ Public Law 112-141 (2012).
\28\ Id. at section 31202(a)(2) (repealing portion of 49 U.S.C.
30124).
\29\ Id. at section 31503. Authority has been delegated to
NHTSA. 49 CFR 1.95.
\30\ Section 30111 requires that a Motor Vehicle Safety Standard
meet the need for safety, be stated in objective terms, and be
practicable, among other requirements. See infra Section IV.
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In 2019, NHTSA published an Advance Notice of Proposed Rulemaking
(ANPRM) seeking comment on a variety of issues related to potential
rear seat belt warning requirements.\31\ NHTSA published the NPRM on
September 7, 2023.\32\
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\31\ 84 FR 51076 (Sept. 27, 2019) (Docket No. NHTSA-2019-0093).
\32\ 88 FR 61674.
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III. Other Seat Belt Reminder Requirements and Protocols

The Economic Commission for Europe (ECE) has instituted seat belt
warning requirements, and the European New Car Assessment Programme
(Euro NCAP) and the Insurance Institute for Highway Safety (IIHS) have
also included seat belt reminder systems in their respective ratings
protocols. Below we briefly summarize the seat belt reminder provisions
in each of these.
ECE Requirements
The ECE has issued an updated version of Regulation No. 16 \33\
(R16) that requires seat belt reminder systems in all front and rear
seats on new cars.\34\ The seat belt reminder system is required to
have both a start-of-trip warning and a change-of-status warning for
both the rear and front seats, though the exact requirements differ
somewhat for rear and front seats.
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\33\ ECE Regulation No. 16, Revision 10.
\34\ The regulation was introduced in two phases: September 1,
2019 for new vehicle types (i.e., all vehicle models with a new type
approval) and September 1, 2021 for all newly-produced and
registered vehicles.
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Rear seat requirements. R16 specifies a two-level warning. The
first-level warning is a visual warning and the second-level warning is
an audio-visual warning. The first-level warning applies at the start
of a trip and the second-level warning applies when a fastened belt
becomes unfastened during a trip. The first-level warning must activate
when the seat belt of any of the rear seats is not fastened and the
ignition switch or master control switch is activated. The first-level
warning must last at least 60 seconds or until the belt is fastened (or
the seat is no longer occupied, if equipped with occupant detection).
The second-level warning must activate when a belt becomes unfastened
and certain specified speed or distance thresholds are met and must
last for 30 seconds unless other specified criteria are met (e.g., the
belt is re-fastened).
Front seat requirements. The front seat belt warning requirements
are similar to the rear seat warnings, with some differences. First,
the first-level visual warning is only required to last 30 seconds, not
60 seconds. Second, the second-level audio-visual warning applies to
unfastened belts at the start of the trip as well as to changes in belt
status (i.e., a fastened belt that becomes unfastened).
The regulation also contains a variety of other requirements
relating to the seat belt warning systems (e.g., telltales, exemptions
for certain vehicles and seating positions). R16 also allows for short-
and long-term deactivation of both front and rear warnings.
The ECE requirements are discussed in more detail where relevant in
later sections of this preamble.

Euro NCAP

Euro NCAP introduced seat belt warnings in their assessment
protocol in 2002. The Euro NCAP protocol for Safety Assist systems
describes which features a seat belt reminder must have to qualify for
points in this area of assessment,\35\ which is then used to calculate
the overall vehicle rating.\36\
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\35\ Euro NCAP's overall safety rating is based on four areas of
assessment (Adult Occupant Protection, Child Occupant Protection,
Vulnerable Road Users, and Safety Assist).
\36\ European New Car Assessment Programme Assessment Protocol--
Safety Assist, Safe Driving, Version 10.3, December 2023.

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[[Page 398]]

Rear seat warnings. For rear seats, a visual signal must start once
the ignition switch is engaged. The visual signal must be at least 60
seconds long. Occupant detection is required for rear seats to be
eligible for a score; this is a new requirement that was instituted
after NHTSA published the NPRM. For systems without occupant
detection,\37\ the visual signal must clearly indicate to the driver
which seat belts are in use and not in use. For systems with occupant
detection on all rear seating positions, the visual signal does not
need to indicate the number of seat belts in use or not in use, but the
signal must remain active if a seat belt remains unfastened on any of
the occupied seats in the rear. No visual signal is required if all the
rear occupants are belted. For systems with rear seat occupant
detection, a 30-second audible signal needs to activate before the
vehicle reaches a speed of 25 km/h (15.5 mph) or before it travels 500
meters when any occupied seat has an unbuckled belt. When any seat belt
experiences a change of status at vehicle speeds above 25 km/h (15.5
mph), an audio-visual signal is required, with the visual signal
lasting 60 seconds and the audible warning lasting 30 seconds, unless
certain conditions are met.
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\37\ This language remains in the protocol as a precondition for
receiving a score for seats with occupant detection. In a vehicle
where not all the rear seats are equipped with occupant detection,
if seats without occupant detection do not meet these requirements
the seats with occupant detection would not receive a score.
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Front seat warnings. The Euro NCAP protocol requires that, to
receive points, at the start of a trip the system must provide a visual
seat belt warning that lasts until the belt is fastened \38\ and an
audible warning that activates when certain conditions are met and
generally must last at least about 90 seconds (the exact duration
depends on a variety of specified criteria, such as vehicle speed or
distance travelled). It also specifies an audio-visual change-of-status
warning that meets the requirements of the initial start-of-trip
warning.
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\38\ Section 3.4.2.1.
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Insurance Institute for Highway Safety (IIHS) Protocol
On December 2021, IIHS released its Seat Belt Reminder System Test
and Rating protocol.\39\ It sets out general requirements for the seat
belt reminder visual and audible signals for front outboard and rear
seating positions. It specifies that a visual signal must be displayed
in the instrument panel, overhead panel, or center console, indicating
an unfastened belt. The audible warning must begin if the seat belt is
unfastened at ignition and for change-of-status, and can cease when the
seat belt is unfastened, the vehicle is no longer in motion, or the
seat is no longer occupied. The protocol also has sound pressure level
and frequency requirements for the audible warning.
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\39\ Insurance Institute for Highway Safety. (April 2024.) Seat
Belt Reminder System Test and Rating Protocol, Version III,
available at <a href="https://www.iihs.org/media/f15e5be9-ac62-4ea6-a88d-7511105bfff5/H3hGKQ/Ratings/Protocols/current/Seat%20Belt%20Reminder%20Test%20Protocol.pdf">https://www.iihs.org/media/f15e5be9-ac62-4ea6-a88d-7511105bfff5/H3hGKQ/Ratings/Protocols/current/Seat%20Belt%20Reminder%20Test%20Protocol.pdf</a> (last accessed May 16,
2024).
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For the rear seats, the IIHS protocol specifies that the visual
signal must activate within 10 seconds of the ignition being turned on,
that the signal must indicate whether the seat belt at each rear
seating position is fastened or unfastened, and that it must last at
least 60 seconds. It does not require a visual signal if the seat belts
at all occupied rear seats are fastened or if no rear occupants are
present. It allows the visual signal to be cancelled by the driver. For
a seat belt change-of-status in the rear seats when the vehicle is in
motion, it requires an audible and visual signal that lasts at least 30
seconds. It further specifies that the audible and visual signal can
stop when seat belts at the occupied rear seats are fastened, the
vehicle is no longer in motion, or the seats are no longer occupied.
For the front seats, under the IIHS ratings protocol, the primary
audible reminder signal for the front outboard seats must be at least
90 seconds in total duration to obtain an ``acceptable'' or ``good''
rating.
Unlike Euro NCAP, the IIHS rating system provides ratings (Poor,
Marginal, Acceptable, and Good) instead of points. For instance, if the
front-passenger seat has an audible signal that lasts less than 8
seconds it would be given a ``Poor'' rating. For a ``Good'' rating both
the driver and front-passenger belt reminder must have an audible
signal that lasts at least 90 seconds and meet the rest of the belt
reminder system requirements for an ``Acceptable'' rating, including
the requirements for a rear seat belt reminder system. Accordingly, a
vehicle cannot receive a ``Good'' rating without having a rear seat
belt reminder system, and a rear seat belt reminder system is not
required for all the other ratings. The protocol does not specify
occupancy criteria (that is, the smallest occupant (or the size and
weight corresponding to the smallest occupant)) that the system must be
able to detect.

IV. Statutory Authority

NHTSA is issuing this final rule pursuant to its authority under
the National Traffic and Motor Vehicle Safety Act (Safety Act). Under
49 U.S.C. chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 et seq.),
the Secretary of Transportation is responsible for prescribing motor
vehicle safety standards. The responsibility for promulgation of FMVSS
is delegated to NHTSA.\40\
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\40\ See 49 CFR 1.95.
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Section 30111 of the Safety Act requires that an FMVSS be
practicable, meet the need for motor vehicle safety, and be stated in
objective terms.\41\ The Safety Act defines ``motor vehicle safety'' as
``the performance of a motor vehicle or motor vehicle equipment in a
way that protects the public against unreasonable risk of accidents
occurring because of the design, construction, or performance of a
motor vehicle, and against unreasonable risk of death or injury in an
accident, and includes nonoperational safety of a motor vehicle.'' \42\
``Motor vehicle safety standard'' means a minimum performance standard
for motor vehicles or motor vehicle equipment.\43\ When prescribing
safety standards, the Secretary must consider all relevant, available
motor vehicle safety information.\44\ The Secretary must also consider
whether a proposed standard is reasonable, practicable, and appropriate
for the types of motor vehicles or motor vehicle equipment for which it
is prescribed, and the extent to which the standard will further the
statutory purpose of reducing traffic accidents and associated
deaths.\45\
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\41\ 49 U.S.C. 30111(a).
\42\ 49 U.S.C. 30102(a)(9).
\43\ Section 30102(a)(10).
\44\ Section 30111(b)(1).
\45\ Section 30111(b)(3)-(4).
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The statutory criterion of practicability is multidimensional. Most
relevant to this rule, it means that in issuing this final rule, NHTSA
must balance benefits and costs, with safety as the preeminent
consideration.\46\ This requirement means that NHTSA ought not simply
choose the least costly regulatory option.\47\ It also means that

[[Page 399]]

the final rule must be reasonably feasible, both economically \48\ and
technologically.\49\ Importantly, however, the Safety Act does allow
NHTSA to issue technology-forcing safety standards.\50\ NHTSA must also
consider the public acceptability of safety standards \51\ and provide
adequate lead time.\52\
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\46\ See, e.g., Motor Vehicle Mfrs. Ass'n of U.S., Inc. v. State
Farm Mut. Auto. Ins. Co., 463 U.S. 29, 55 (1983) (``The agency is
correct to look at the costs as well as the benefits of Standard 208
. . . When the agency reexamines its findings as to the likely
increase in seatbelt usage, it must also reconsider its judgment of
the reasonableness of the monetary and other costs associated with
the Standard. In reaching its judgment, NHTSA should bear in mind
that Congress intended safety to be the preeminent factor under the
Motor Vehicle Safety Act.'').
\47\ See, e.g., Public Citizen, Inc. v. Mineta, 340 F.3d 39, 58
(2nd Cir. 2003) (``The notion that `cheapest is best' is contrary to
State Farm. There the Court instructed NHTSA `to look at the costs
as well as the benefits' of motor vehicle safety standards, and to
``bear in mind that Congress intended safety to be the pre-eminent
factor under the [Safety Act.] Thus, when NHTSA issues standards
under the Safety Act, State Farm requires that the agency weigh
safety benefits against economic costs; moreover, State Farm
instructs the agency to place a thumb on the safety side of the
scale.'') (quoting Motor Vehicle Mfrs. Ass'n of U.S., Inc., 463 U.S.
at 54) (citations omitted).
\48\ See, e.g., Public Citizen, Inc. v. Mineta, 340 F.3d at 58
(2nd Cir. 2003) (``The committee recognizes . . . that the Secretary
will necessarily consider reasonableness of cost, feasibility and
adequate lead time.'') (quoting H. Rep. No. 1776, at 16 (1966)).
\49\ See, e.g., Paccar, Inc. v. Nat'l Highway Traffic Safety
Admin., 573 F.2d 632, 635 n.5 (9th Cir. 1978) (``Practicable is
defined to require consideration of all relevant factors, including
technological ability to achieve the goal of a particular
standard[.]'') (citations and quotations omitted) (quoting H.R. Rep.
No. 1776, 89th Cong., 2d Sess. 16 (1966)).
\50\ Chrysler Corp. v. Dep't of Transp., 472 F.2d 659, 673 (6th
Cir. 1972) (``[T]he Agency is empowered to issue safety standards
which require improvements in existing technology or which require
the development of new technology, and it is not limited to issuing
standards based solely on devices already fully developed.'').
\51\ Pac. Legal Found. v. Dep't of Transp., 593 F.2d 1338, 1345-
46 (D.C. Cir. 1979) (``We believe that the agency cannot fulfill its
statutory responsibility unless it considers popular reaction.
Without public cooperation there can be no assurance that a safety
system can meet the need for motor vehicle safety.'') (quotations
and citations omitted).
\52\ 2 U.S. Code Cong. & Adm. News, 89th Cong., 2d Sess., 1966,
p. 2714, quoted in H & H Tire Co. v. U. S. Dep't of Transp., 471
F.2d 350, 353 (7th Cir. 1972). (``The committee recognizes . . .
that the Secretary will necessarily consider [in the issuance of
standards] reasonableness of cost, feasibility and adequate lead
time.'').
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In developing this final rule, the agency carefully considered
these statutory requirements and has concluded that it meets them. They
are discussed in more detail throughout the preamble and in the
regulatory analyses where relevant.

V. Summary of the NPRM

The NPRM had two main components. The first proposed requiring a
seat belt reminder for the rear seats. The second proposed changes and
enhancements to the seat belt warning requirements for the front
outboard seats, most notably an audio-visual warning that persists
until the seat belt at any occupied front outboard seat is fastened.
These proposed requirements would apply to passenger cars and trucks,
buses (except school buses), and MPVs with a GVWR of 4,536 kg (10,000
lb) or less.

Rear Seat Belt Reminder Requirements

The first component of the NPRM was a set of proposed requirements
for a seat belt warning for rear seats. The proposed requirements had
four main elements.
<bullet> Visual warning on vehicle start-up to inform the driver of
the status of the rear seat belts. We proposed three different
compliance options from which manufacturers could choose for the rear
seat belt warning system. The first would require the system to
indicate how many or which rear seat belts are in use (the ``positive-
only'' option). The second would require the system to indicate, for
the occupied rear seats, how many or which rear seat belts are not in
use (the ``negative-only'' option). The third would require the system
to indicate, for the occupied rear seats, how many or which rear seat
belts are in use and how many or which rear seat belts are not in use
(the ``full-status'' option). Certain features would be required of all
the options. Each system would have to provide a continuous or flashing
visual warning, consisting of either icons or text, visible to the
driver. The visual warning would have to last for at least 60 seconds,
beginning when the vehicle's ignition switch is moved to the ``on'' or
``start'' position. All the systems would require that the vehicle be
equipped with technology to determine that the belt latch is
fastened.\53\ The negative-only and full-status compliance options
would additionally have required that the vehicle be equipped with an
occupant detection system (which facilitates these more informative
warnings).
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\53\ We note the preamble language imprecisely indicated the
necessity for a belt latch sensor. As discussed later in this
document, it was not our intention to require a specific technology.
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<bullet> Audio-visual change-of-status warning. We proposed an
audio-visual warning whenever a fastened rear seat belt is unfastened
while the ignition switch is in the ``on'' or ``start'' position and
the vehicle's transmission selector is in a forward or reverse gear.
The warning would have to last for at least 30 seconds. We did not
propose any requirements for the volume or tone of the warning. The
intent of this warning was to alert the driver or other occupants to a
change in belt status during a trip. The warning would not be required
if a door is open, which would be the case if a rear passenger
unfastened their belt in order to exit the vehicle.
<bullet> Requirements related to electrical connections. We
proposed to require that readily removable rear seats either
automatically re-establish the necessary electrical connections, or, if
a manual connection is required, have readily accessible connectors.
Further, vehicles with the negative-only compliance option would be
required to provide a visual warning to the driver if a proper
electrical connection has not been established for a readily removable
rear seat.
<bullet> Owner's manual requirements. We proposed that the vehicle
owner's manual (which includes information provided by the vehicle
manufacturer to the consumer, whether in digital or printed form)
describe the warning system's features (including the location and
format of the visual warnings) and include instructions on how to make
any manual electrical connections for readily removable seats.

Front Outboard Seat Belt Warning Requirements

The NPRM included several enhancements to the seat belt warning
requirements for the front outboard seats. We proposed three main
changes.
<bullet> Audio-visual warning on vehicle start-up for front
outboard passenger seat. We proposed to require a seat belt warning for
the front outboard passenger seat.
<bullet> Increasing the duration of the audio-visual warning on
vehicle start-up. We proposed enhancing the front seat warning
requirements by requiring an audio-visual warning that remains active
until the seat belt at any occupied front outboard seat is fastened.
Vehicle manufacturers could adjust the characteristics of the auditory
warning signal (such as frequency and volume) to make the warning both
effective and acceptable to consumers. The proposal included specific
duty cycle characteristics.
<bullet> Audio-visual change-of-status warning. We also proposed to
require an audio-visual change-of-status warning whenever a front
outboard seat belt is unbuckled during a trip (unless a front door is
open, to account for an occupant unfastening the belt to exit the
vehicle). The warning would be required to remain active until the seat
belt is refastened.

Proposed Compliance Date

We proposed a compliance date for the amendments to FMVSS No. 208,
``Occupant crash protection,'' as follows. Manufacturers would be
required to comply with the amendments as of the first September 1 that
is one year after the publication of the final rule for the front seat
belt warning system requirements and the first September 1 that is two
years after the publication of the final rule for the rear seat belt
warning system requirements, with optional early

[[Page 400]]

compliance. Multi-stage manufacturers and alterers would have an
additional year to comply.

Regulatory Alternatives

NHTSA considered alternatives to the proposed requirements. The
main alternatives NHTSA considered were the seat belt warning
requirements in ECE R16 and Euro NCAP. The proposed requirements were
identical or similar to ECE R16 and Euro NCAP in many respects but
differed from them in several ways. For instance, while the ECE rear
seat belt warning regulations allow a warning for an unfastened seat
belt at an unoccupied seat, the proposal would not allow this, because
we tentatively believed that the resulting ``false'' warning would
potentially annoy drivers and lead to behaviors that would decrease
system effectiveness. Another way the proposal differed from ECE R16 is
the duration of the front seat belt warning on vehicle start-up: R16
generally requires only a 30-60 second audio-visual warning; NHTSA
proposed a warning that lasts until the seat belt is buckled.

VI. Final Rule and Response to Comments

A. Rear Seat Belt Warning Requirements

1. Applicability
The proposal applied to all rear designated seating positions in
passenger cars and all rear designated seating positions certified to a
compliance option requiring a seat belt in trucks, buses, and MPVs with
a GVWR of 4,536 kg (10,000 lb) or less, except for school buses and law
enforcement vehicles. NHTSA's regulations define a bus as a vehicle
designed for carrying more than ten persons.\54\ The proposal included
small buses, which refers to buses with a GVWR not more than 10,000 lb;
this therefore includes high-capacity vans. However, the proposal did
not include medium-sized buses (with a GVWR 10,000 lb-26,000 lb) or
large buses (with a GVWR greater than 26,000 lb). We proposed to apply
the proposed requirements to the specified categories of vehicles
because these vehicles are required to have seat belts at all rear
designated seating positions and (except for some buses) a seat belt
warning for the driver's seat. We noted that some types of trucks and
MPVs (motor homes, walk-in van-type trucks, vehicles designed to be
sold exclusively to the U.S. Postal Service, or vehicles with a GVWR
between 8,500-10,000 lb carrying a chassis-mount camper) \55\ and over-
the-road buses that are also prison buses \56\ are not required to have
rear seat belts. In the NPRM we explained that we did not propose to
exempt special-purpose vehicle types such as ambulances because NHTSA
believed that they are typically customized after first sale.
---------------------------------------------------------------------------

\54\ 49 CFR 571.3 (``Bus means a motor vehicle with motive
power, except a trailer, designed for carrying more than 10
persons.'') (italics in original).
\55\ S4.2.7.1.
\56\ S4.4.3.3; S4.4.5.1.
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The proposed applicability was largely consistent with ECE R16,
with a few differences. The rear seat belt reminder requirements in R16
do not include vehicles that carry more than nine persons (including
the driver).\57\ There is also no weight specification for the
passenger vehicles to which R16 applies. R16 also exempts ``ambulances,
hearses, and motor-caravans as well as for all seats for vehicles used
for transport of disabled persons, vehicles intended for use by the
armed services, civil defense, fire services and forces responsible for
maintaining public order.'' \58\
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\57\ Section 8.4.1.2 (rear seat belt warning requirements apply
to M<INF>1</INF> and N<INF>1</INF> category vehicles); Consolidated
Resolution on the Construction of Vehicles (R.E.3) Revision 6,
Section 2.2.1 (category M<INF>1</INF> vehicles) (``Vehicles used for
the carriage of passengers and comprising not more than eight seats
in addition to the driver's seat.'') and Section 2.3.1 (category
N<INF>1</INF> vehicles) (``Vehicles used for the carriage of goods
and having a maximum mass not exceeding 3.5 tonnes [7,716 lb].'').
\58\ Section 8.4.1.3.
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Comments
NHTSA received comments that supported the proposal; comments that
recommended expanding the applicability; and comments that recommended
excluding additional vehicle types.
Some commenters specifically supported various aspects of the
proposal. Freedman Seating Company (FSC) and Mr. Koo supported the
vehicles covered by the proposal and Ms. Tombrello supported including
van-like buses because she believed some have been prone to misloading
of passengers and baggage. Mr. Stange agreed that the final rule should
exclude medium and large buses, due to the distraction the system would
create for the driver; problems with maintenance and sensor
reliability; and the fact that bus passengers are not required to wear
seat belts in some states.
Some commenters argued for including additional higher-capacity
vehicles that the proposal excluded. The National Safety Council (NSC)
and Ms. Tombrello supported including school buses (regardless of
weight) and Mr. Koo supported including school buses with a GVWR 10,000
lb and under. FSC supported extending the requirements to over-the-road
buses with a GVWR between 10,000 and 26,000 lb (except school,
perimeter seating and transit buses). NSC commented that the final rule
should include limousines. Relatedly, InterMotive Vehicle Controls
(InterMotive) commented that it manufactures an aftermarket seat belt
reminder system for buses and vans with a GVWR both below and above
10,000 lb.
On the other hand, some comments argued for excluding additional
vehicles from the requirements. The Alliance for Automotive Innovation
(Auto Innovators) and Mercedes-Benz and Mercedes-Benz Research and
Development North America (Mercedes) recommended exempting vehicles
with more than six rear seats or more than two rear rows, pointing to
challenges with providing the driver with the status information on all
seating positions via the instrument panel (or other in-vehicle
display) due to the number of seats that may need to be displayed. Auto
Innovators further commented that for high-occupancy vehicles with
removeable seats, an electronic control unit and other hardware are
needed, which leads to practicability concerns, including increased
costs for customers. Mercedes reiterated these practicability concerns.
The Recreational Vehicle Industry Association (RVIA) similarly
commented that this final rule should harmonize with R16 and not apply
to motor homes. RVIA raised several different issues specific to motor
homes. First, it explained that motor homes are used in unique ways
because they are used both for transportation and for temporary,
recreational, and seasonal use. As an example, RVIA discussed a
scenario where occupants are seated in a rear seating position with the
motor home turned on, but where the vehicle remains stationary, leading
to a false warning. Second, it commented that motor homes' rear seats
are often used for storage, which could again lead to false warnings.
Third, RVIA commented that, because motor homes are often equipped with
non-conventional seats that convert into a bed, developing wiring and
sensors that would not be damaged in the conversion process would be
challenging if not impossible. Fourth, RVIA commented that the rear
portion of a motor home also has its own electrical system with very
little interface with the chassis electronics. This lack of interface
between electrical systems is unique in comparison to other types of
vehicles that typically have seats installed in standard

[[Page 401]]

configurations in the same factory as the vehicle is assembled,
completed, and shipped. RVIA stated that there is currently not a way
to provide electronic signals from the seating positions in the rear
portion of the motor home to the sophisticated electronics controls
that are proprietary to the chassis manufacturers.
Finally, Braun Northwest (BNW) commented that the final rule should
exempt ambulances, giving essentially two different reasons. First, BNW
commented that the reason NHTSA gave for not exempting ambulances--that
they are typically customized after first sale--was factually
inaccurate. BNW commented that while some special-purpose vehicles may
be customized after first sale, that is not the case with ambulances.
BNW explained that data from the Ambulance Manufacturer's Division of
the National Truck Equipment Association indicates that van ambulances
with a GVWR under 10,000 lb, which would be affected by this NPRM,
comprise more than 20 percent of the annual production of United States
ambulance manufacturers. Second, BNW pointed out that, while circuited
buckles needed for seat belt buckle status indication are commonly
available and simple to install on the two- and three-point seat belts
commonly used on most vehicles, they are inherently problematic on the
four, five, and six-point belts needed on ambulances. BNW explained
that recent work facilitated by NHTSA resulted in a new SAE
International (SAE) recommended practice, SAE J3026 Ambulance Patient
Compartment Seating Integrity and Occupant Restraint, developed
specifically for testing occupant restraint systems in ambulances. All
three national ambulance standards (KKK-A-1822F, Federal Specification:
Star-Of-Life Ambulance; NFPA 1917 Standard for Automotive Ambulances;
and CAAS Ground Vehicle Standard) now require compliance with SAE
J3026. BNW indicated that the critical ramification of SAE J3026 for
the NPRM was that side-facing ambulance bench seats must be fitted with
four-point, five-point, or six-point seat belts. BNW commented that
there are practicability concerns with enabling buckle status
indication for these seat belts, including the problem of getting wires
from an emergency locking seat belt retractor to a circuited buckle
located at the center front of the occupant's torso. Additionally, BNW
argued that seat belt reminders may prevent medical personnel from
administering medical care, as changes in occupant position required to
render patient care would cause alarm indications that add distraction
and confusion in an environment where such distractions can have dire
consequences.
Agency Response
NHTSA is adopting the proposal except that the final rule contains
an additional exemption for ambulances.
The major difference between the vehicles to which R16 and the
final rule apply is that the final rule applies to small buses, which
typically include buses with up to about four rear rows--mainly high-
capacity passenger vans (10 to 15-passengers), such as Chevrolet
Express, Ford Transit, GMC Savana, and Mercedes Sprinter passenger
vans. However, because the rule applies only to vehicles with a GVWR
less than 10,000 lb, it would generally not include vehicles with more
than four rows.
We believe that including small buses such as these high-capacity
vans addresses an important safety need. As we explained in the NPRM,
we believe it is particularly important to include vehicles with a GVWR
greater than 3,855 kg (8,500 lb), but less than or equal to 4,536 kg
(10,000 lb), because this range includes high-occupancy vehicles.
Including these vehicles is important because an increasing number of
high-occupancy vehicles are used as personal vehicles and are not
solely used for work-related purposes.\59\ In addition, multiple rear
seats or rows make it more difficult for the driver to ascertain rear
seat belt use, so a warning could prove especially useful in these
vehicles. We think this requirement would be especially beneficial for
15-passenger vans, for which there is both an increased risk of
rollover (related to the occupancy level of these vehicles) and lower
seat belt use rates compared to other passenger vehicles.\60\
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\59\ See, e.g., <a href="https://media.ford.com/content/fordmedia/fna/us/en/news/2016/07/29/nothing-mini-about-this-van--ford-transit-attracts-large-familie.html">https://media.ford.com/content/fordmedia/fna/us/en/news/2016/07/29/nothing-mini-about-this-van--ford-transit-attracts-large-familie.html</a> (last accessed May 16, 2024).
\60\ Belt use rates among occupants in 15-passenger vans
involved in fatal crashes are significantly lower compared to other
passenger vehicles. See Subramanian, R. (2008). Fatalities to
Occupants of 15-Passenger Vans, 1997-2006. (Report No. DOT-HS 810
947). National Highway Traffic Safety Administration.
---------------------------------------------------------------------------

Providing a reminder in vehicles with multiple rear rows is
technically feasible. As we noted above, because the final rule applies
to vehicles with a GVWR 10,000 lb or less, it generally would not
include vehicles with more than four rear rows of seats, which should
make it easier to implement a reminder. We are unaware of any currently
produced full-size passenger vans having a rear seat belt reminder
system. We did find aftermarket solutions from abroad for medium to
large buses,\61\ and InterMotive commented that a seat belt warning
system already exists for multipurpose passenger vehicles with a GVWR
both below and above 10,000 lb. They currently manufacture an after-
market solution, SeatLink, for the bus and van market, including seats
supplied by Freedman Seating Company (Freedman). However, we do not
have any information on the performance and reliability of these
systems.
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\61\ See <a href="https://www.phoenixseating.com/our-products/all-buckled-up">https://www.phoenixseating.com/our-products/all-buckled-up</a> and <a href="https://www.fsrtek.com/applications/bus-seat-belt-alarm-system">https://www.fsrtek.com/applications/bus-seat-belt-alarm-system</a> (last accessed May 16, 2024).
---------------------------------------------------------------------------

We do acknowledge that vehicles such as high-capacity vans may
encounter visual signal complexities. Accordingly, our intent was to
propose performance requirements that provide manufacturers with the
flexibility to design a warning system that is appropriate for each
vehicle type (for example, the final rule does not require a full
schematic of the rear seats). For example, a visual warning option for
vehicles with multiple rows could be the seat belt icon with an
adjacent number corresponding to how many rear seat belts are fastened.
In addition, as we explain in more detail below (see Section
VI.A.2.a.i), in response to the comments, we have expanded the
compliance options to allow additional types of visual warning systems.
This too should help address any concerns related to feasibility.
The final rule, however, also follows the proposal in excluding
school buses and medium and large buses. As we explained in the NPRM,
extending the requirements to school buses would place additional cost
burden on school systems and may result in reductions in service; would
place additional burdens on the driver; and raises liability issues and
the potential for buses being out of service due to malfunctioning
systems. Many of these concerns were raised by commenters to the ANPRM
and we believe these concerns are still valid. Moreover, as we also
pointed out in the NPRM, school buses use compartmentalization, which
provides protection even to unbelted occupants. Similarly, the final
rule also excludes medium and large buses because of issues such as
those noted by Mr. Stange, including cost, reliability, and driver
burden.
The final rule also follows the proposal by including motor homes.
As an initial matter, we note that some motor homes are not required to
have

[[Page 402]]

rear seat belts so the requirements will not necessarily apply to all
motor homes. In addition, the seat belt requirements do not apply to
seats in motor homes with a GVWR over 10,000 lb and classified as MPVs
which the manufacturer designates and conspicuously labels as not
intended for occupancy while the vehicle is in motion.\62\ Accordingly,
such vehicles are not subject to the requirements in this rule.
Although we recognize that R16 exempts motor homes (motor caravans), we
see no reason to exclude from this rule designated seating positions
(DSPs) in motor homes that are required to have seat belts. Those DSPs
are designed to have passengers while the vehicle is in motion. Such
occupants would benefit from a seat belt and therefore, from a seat
belt reminder. We note that if the motor home is turned on for other
purposes than driving, the start-up warning is a 30-second visual
warning that should not be unduly annoying.
---------------------------------------------------------------------------

\62\ 49 CFR 571.3 (definition of ``designated seating
position''); FMVSS No. 207 S4.4.
---------------------------------------------------------------------------

Limousines, depending on their characteristics, may also be covered
by the rule. Limousines are not currently a vehicle class defined in
the FMVSS. Depending on its characteristics, a limousine might be
classified as a passenger car, MPV, or bus.\63\ Generally, a passenger
car is designed for carrying 10 or fewer persons, an MPV is a vehicle
carrying 10 or fewer persons which is constructed either on a truck
chassis or with certain special features, and a bus is designed to
carry more than 10 persons. The final rule encompasses all these
vehicle types, so a limousine would be covered by the requirements as
long as it weighed 10,000 lb or less. At the same time, the FMVSS
generally apply to new vehicles, including new vehicles that are
altered, or vehicles manufactured in more than one stage. Limousines
(such as ``stretch'' limousines) that are the result of modifications
made to a vehicle after first purchase other than for resale would not
be required to be certified to the seat belt reminder requirements for
seating positions that are added in the modification process.\64\
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\63\ 49 CFR 571.3.
\64\ The Infrastructure, Investment and Jobs Act, H.R. 3684,
Sections 23015, 23023 (117th Congress) (2021), contains two
provisions that direct NHTSA to conduct research and issue rules (if
such rules would meet the criteria in section 30111 of the Safety
Act) related to various aspects of limousine crashworthiness and
occupant protection. NHTSA's research in these areas is ongoing.
See, e.g., DOT Regulatory Agenda, Fall 2023, RIN 2127-AM48, ``Seat
Belts in Limousines,'' available at <a href="https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202310&RIN=2127-AM48">https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202310&RIN=2127-AM48</a> (last accessed
December 16, 2024). The law also directs that the rules issued
pursuant to it apply to modified vehicles. However, that law also
defines the term ``limousine'' to, among other things, refer to
vehicles weighing between 10,000 and 26,000 lb. This would therefore
not include any limousines that are covered by this final rule,
which is limited to vehicles up to 10,000 lb. GVWR.
---------------------------------------------------------------------------

The one way the final rule does depart from the proposal with
respect to the applicability is by including an exemption for
ambulances from the rear seat belt warning system requirements.\65\
Given the information provided by BNW, the original intent of the rule
not applying to ambulances, and the fact that excluding ambulances
harmonizes with ECE R16, the final rule exempts ambulances. Although
neither FMVSS No. 208 nor 49 CFR 571.3 defines ``ambulance,'' FMVSS No.
201, ``Occupant protection in interior impact,'' defines it to mean ``a
motor vehicle designed exclusively for the purpose of emergency medical
care, as evidenced by the presence of a passenger compartment to
accommodate emergency medical personnel, one or more patients on
litters or cots, and equipment and supplies for emergency care at a
location or during transport.'' \66\ We are including a cross-reference
to this definition in the regulatory text. However, we have not
included a broader carve-out for emergency vehicles. We did not receive
any comments indicating that such a carve-out was necessary. Moreover,
there are a number of ways that owners and purchasers of emergency
vehicles for official purposes could disable the warnings. These owners
and purchasers already sometimes alter vehicles significantly.\67\
---------------------------------------------------------------------------

\65\ This does not exempt ambulances from the front seat belt
warning requirements.
\66\ FMVSS No. 201, S3 (definitions).
\67\ Although section 30122 of the Safety Act prohibits making
inoperative required safety devices, this prohibition does not apply
to vehicle owners. See infra n. 91 and accompanying text.
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2. Requirements
The NPRM proposed a 60-second visual warning on vehicle start-up; a
30-second audio-visual warning if a buckled belt is unfastened during a
trip; and requirements or criteria related to readily removable seats,
the owner's manual instructions, the location of the telltale, and how
NHTSA would determine that a belt was or was not in use. We discuss
these requirements in turn below.
a. Visual Warning on Vehicle Start-Up
The NPRM proposed a 60-second visual warning on vehicle start-up
that would inform the driver of how many or which seat belts are and/or
are not in use. We proposed three different compliance options for the
type of information conveyed to the driver. Occupant detection would
not be required for one of the three compliance options. The warning
would be triggered when the ignition is placed in the ``on'' or
``start'' position. When testing a system certified to one of the
compliance options necessitating occupant detection, NHTSA would seat a
dummy or human occupant corresponding to a 6-year-old. We discuss these
proposed requirements below in more detail.
i. Type of Information Conveyed by the Visual Warning and Whether
Occupant Detection Should Be Required
The proposed requirements for the rear seat belt warning system
(RSBWS) included a visual warning that would activate on vehicle start-
up to inform the driver of the status of the rear seat belts. We
proposed three different compliance options. The first would require
the system to indicate how many or which rear seat belts are in use
(the ``positive-only'' option). The second would require the system to
indicate, for the occupied rear seats, how many or which rear seat
belts are not in use (the ``negative-only'' option). The third would
require the system to indicate, for the occupied rear seats, how many
or which rear seat belts are in use and how many or which rear seat
belts are not in use (the ``full-status'' option). The negative-only
and full-status compliance options would require that the rear seats be
equipped with a mechanism to determine when a belt latch is fastened
and an occupant detection system (which facilitates these more-
informative warnings), while the positive-only option would only
require that the rear seats be equipped with a mechanism to determine
when a belt latch is fastened.
In the NPRM we stated that we had tentatively decided not to
require occupant detection in the rear seats because occupant detection
continued to present technical challenges which could reduce the
effectiveness and/or acceptance of these systems. This tentative
decision was also based on factors such as the needed increase in seat
belt use for this regulatory alternative to have positive net benefits.
Because we did not propose to require occupant detection, we also did
not propose requiring enhanced warnings (such as an audible warning on
vehicle start-up).
The proposal harmonized with ECE R16 and Euro NCAP in a variety of
ways, but also deviated from them in some respects.

[[Page 403]]

ECE R16 requires a visual warning at the start of a trip. That
warning ``indicate[s] at least all rear seating positions to allow the
driver to identify, while facing forward as seated on the driver seat,
any seating position in which the safety-belt is unfastened.'' \68\
Occupant detection is not required, but in vehicles that do have
occupant detection the warning does not need to indicate unfastened
belts for unoccupied seating positions.\69\
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\68\ Section 8.4.4.2.
\69\ Section 8.4.4.2.
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The Euro NCAP rating protocol also requires a visual warning at the
start of a trip. The requirements are similar to ECE R16. However, Euro
NCAP's rating protocol was recently revised to require occupant
detection in the rear seat to receive points for this feature. For
systems without occupant detection, the visual signal must clearly
indicate to the driver the seating positions showing the rear seat
belts in use and not in use. (These seats would not be eligible for
points, but in order for seats with occupant detection to receive
points the seats without occupant detection would have to meet these
requirements.) For systems with occupant detection, the visual signal
does not need to indicate the number of seat belts in use or not in
use, but the signal must remain as long as the seat belt remains
unfastened on any of the occupied seats in the rear.\70\ No signal is
required if all of the rear occupants are belted \71\ or no rear
occupants are detected.\72\
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\70\ Section 3.4.3.1.3.
\71\ Section 3.4.3.1.4.
\72\ Section 3.4.3.1.1.
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The IIHS rating protocol requires a visual signal indicating
``whether the seat belt at each rear seating position is fastened or
unfastened.'' \73\
---------------------------------------------------------------------------

\73\ Seat Belt Reminder System Test and Rating Protocol, Version
III at pg. 7.
---------------------------------------------------------------------------

The NPRM acknowledged that the proposed compliance options were not
consistent with all seat belt warning systems currently deployed in the
U.S. and Europe or with Euro NCAP's requirements. Specifically, we
noted that manufacturers appeared to be deploying systems that would be
categorized as either positive-only or negative-only except without
occupant detection, the latter of which would not be permitted under
the proposed compliance options. We also noted that the positive-only
compliance option did not appear to be consistent with Euro NCAP
because Euro NCAP requires that systems without occupant detection show
the rear seat belts in use and not in use, and the positive-only
compliance option would not permit a visual signal for an unfastened
seat belt.
Accordingly, while we tentatively concluded that the proposed
compliance options would help mitigate false warnings and the possibly
attendant consumer acceptance issues, we explained that we were
considering altering the proposed compliance options to accommodate
systems that are currently being deployed, or that manufacturers may
wish to deploy in the future.
Comments
Auto Innovators, General Motors (GM), American Honda Motor Co.
(Honda), and Hyundai America Technical Center, Inc. (HATCI) generally
supported including multiple compliance options in the final rule.
Freedman, Automotive Safety Council (ASC), Tesla, Advocates and Public
Citizen, and the National Automobile Dealers Association (NADA)
generally supported the proposed compliance options, although as noted
below some of these commenters preferred certain compliance options or
requested that additional compliance options be added.
Several commenters (Consumer Reports, Safe Kids Worldwide (SKW),
Paradise, NSC, Safe Ride News (SRN), Cross, and Ms. Tombrello) argued
that NHTSA should require occupant detection in the rear seats. Other
commenters (Freedman, IEE,\74\ ASC), while not explicitly recommending
that occupant detection be required, either preferred options requiring
occupant detection or focused on the benefits and feasibility of rear-
seat occupant detection. These commenters made a variety of arguments.
---------------------------------------------------------------------------

\74\ A supplier of automotive sensing systems.
---------------------------------------------------------------------------

Some commenters argued that the necessary technology for occupant
detection is feasible. Consumer Reports commented that occupant
detection does not pose unreasonable technical challenges, and is not
prohibitively expensive (see Section VIII, Overview of Costs and
Benefits). Consumer Reports and Mr. Paradise commented that rear-seat
occupant detection technology is already widely available; Mr. Paradise
also noted that 7 percent of vehicles already have the technological
capability of occupant detection in rear seats. NSC commented that
challenges with false positives (e.g., transportation of cargo and
pets) can be addressed through a relatively small investment, such as
with low-cost 2-D or digital cameras, and that costs would further
decrease over time if it were required. Consumer Reports noted that
occupant detection is already widely deployed in the front outboard
passenger seats. Relatedly, although not recommending that occupant
detection be required, IEE commented that today's occupant detection
sensors, predominantly designed for a detection of 5th percentile adult
female, can reliably differentiate occupants from cargo.
Several commenters focused on the benefits of requiring occupant
detection. Consumer Reports, Mr. Paradise, SKW, SRN, ASC, Ms. Cross,
NSC, and Ms. Tombrello commented that warning systems using occupant
detection would be more effective than those without it. Consumer
Reports, Paradise, Ms. Cross, and NSC noted that occupant detection
would enable enhanced warnings, which are more effective.
Accordingly, some of these commenters recommended requiring the
proposed full-status and/or negative-only options that required
occupant detection. Consumer Reports argued that NHTSA should require
the full-status compliance option because the ``positive-only'' and
``negative-only'' compliance options are insufficient to incentivize
rear seat belt use. Consumer Reports commented that the positive-only
option would be the least technically complex, but it would also be the
least effective type of warning system (because it creates unnecessary
mental work for the driver and allows room for human error). Consumer
Reports further explained that the positive-only system would be a
departure from Euro NCAP, which requires that systems without occupant
detection show both the rear seat belts in use and those not in use.
Consumer Reports also commented that given that both the negative-only
and the full-status options require a belt latch sensor and an occupant
detection system, the negative-only option should be eliminated because
the full-status option is more informative and effective. SRN, ASC,
NSC, and Ms. Cross similarly commented that NHTSA should require
negative-only or full-status systems, which would be more effective in
alerting caregivers to an unbuckled rear passenger than ``positive-
only'' systems. Ms. Cross commented that negative-only and full-status
systems can inform the driver whether any rear seat occupants are
unbuckled without having to make a comparison between number of seats
to the number of occupants and an audible component can be added. ASC
also noted that permitting only negative-only and full-status systems
would harmonize with the requirements in Europe.

[[Page 404]]

Consumer Reports, Cross, and SKW also recommended requiring
occupant detection because that feature could eventually be used for
other safety functions such as rear occupant alerts for vehicular
heatstroke prevention and air bag suppression. SKW and Ms. Cross
pointed to the potential to detect children or other vulnerable
occupants in child safety seats, booster seats, or seat belts.
On the other hand, vehicle manufacturers commented that the final
rule should not require occupant detection. Toyota Motor North America,
Inc. and Toyota Motor Corporation (Toyota) and Auto Innovators
commented that an occupant detection system can introduce false
positives. Several manufacturers requested removing the requirement for
occupant detection from one or both of the proposed compliance options
that required it (full-status and negative-only).
Toyota argued that NHTSA should allow negative-only systems without
occupant detection because an occupant detection system does not
provide any additional safety benefit for the negative-only system.
Toyota explained that it is reasonable to anticipate that a driver
knows whether a rear occupant is in the vehicle, and, as with a
positive-only system, can combine that knowledge with the information
from the visual indicator. Toyota also commented that a telltale
indicating a seat belt is not fastened at an unoccupied seat is not a
false positive, but is instead useful information for the driver.
More generally, several manufacturers and trade groups (Auto
Innovators, Ford Motor Company (Ford), Nissan North America (Nissan),
NADA, Honda, Hyundai Motor Company (Hyundai)) commented that NHTSA
should permit manufacturers to convey information on positive belt
status information (i.e., when belt is in use) and/or negative belt
status information (i.e., when the belt is not in use) without occupant
detection--that is, NHTSA should expand the proposed compliance options
to permit negative-only systems without occupant detection and/or full-
status systems without occupant detection.\75\ NADA argued that these
options would provide better contextual information for drivers than
the proposed full[hyphen]status option because they would provide seat
belt status information for all seating positions regardless of
occupancy. Nissan, Ford, and Auto Innovators argued that presenting
information on the seat belt status regardless of whether the seat is
occupied or not should not be deemed as misleading but rather as
furnishing the driver with pertinent contextual information concerning
seat belt usage across all positions. Nissan and Ford argued that this
information would empower the driver to distinguish easily between
buckled and unbuckled seat belts, particularly when compared to the
locations where known passengers are situated in the rear row. Auto
Innovators, Nissan, NADA and Ford commented that this approach would be
consistent with European regulations. Nissan, NADA, and Ford indicated
that this approach would align with ECE R16, and Ford and Auto
Innovators commented that the approach aligns with the IIHS approach.
Honda commented that systems without occupant detection that provide
visual information on both fastened and unfastened seat belts have been
in use in Europe for many years and are well understood by those that
use it regularly. Auto Innovators and NADA commented that not expanding
the compliance options in this way would require development and
deployment of new systems and increase cost and lead time for some
original equipment manufacturers (OEMs), which ultimately harms
consumers and hinders achievement of NHTSA's safety objective. Auto
Innovators further commented that it was unaware aware of any data that
would support NHTSA's claim that a visual indication of an unfastened
seat belt at an unoccupied seat would annoy drivers and argued that if
driver annoyance is a concern, NHTSA should consider allowing a
dismissible initial warning, as is the case with both IIHS and R16.
---------------------------------------------------------------------------

\75\ Some of the comments were ambiguous with respect to whether
they were referring to full-status systems, negative-only systems,
or both.
---------------------------------------------------------------------------

In addition, Ford, Toyota, and Honda raised concerns with the
proposed positive-only compliance option. Ford and Toyota commented
that it conflicts with R16 and the IIHS protocol. Honda commented that
if all rear occupants are unbuckled and there is no indication of their
status, the driver may remain unaware of the system's ability to
support the determination of the statuses of the belts for the rear
occupants.
Agency Response
In response to the comments, the final rule follows the proposal in
not requiring occupant detection, but modifies the proposal by revising
the requirements to allow full-status and negative-only reminder
systems without occupant detection.
The final rule follows the proposal in not requiring that rear seat
belt reminder systems be equipped with occupant detection. There are a
few reasons for this decision.
One reason is that we believe rear-seat occupant detection
continues to present technical challenges. This is especially the case
because we have concluded that rear-seat occupant detection systems
should be able to detect, at a minimum, occupant characteristics
matching a 6-year-old for determining whether a rear seat is occupied.
This standard differs from ECE R16 and Euro NCAP, both of which base
their requirements for occupant detection-equipped rear seat belt
reminder systems on the 5th percentile female. This difference is
discussed in more detail in Section VI.A.2.a.iv, Seat Occupancy
Criteria and Interaction with Child Restraint Systems. Rear-seat belt
reminder systems with occupant detection have only been recently
deployed in vehicles sold in the U.S. (starting in MY 2021 based on our
available data) and are currently offered on only a small proportion of
new vehicles.\76\ Based on the projected sales for MY 2022,
approximately 7 percent of vehicles were equipped with rear-seat
occupant detection. We have no data on how the occupant detection in
these vehicles is working.
---------------------------------------------------------------------------

\76\ NHTSA does not have any specific information on the size of
occupant these systems are designed to detect. However, based on the
manufacturer comments requesting that NHTSA require occupant
detection systems to detect a 5th percentile female occupant, it is
likely that these systems are designed to detect occupants as small
as the 5th percentile female.
---------------------------------------------------------------------------

While occupant detection technology is readily available and
standard equipment in most front outboard passenger seats, the occupant
detection technology used for the front outboard passenger seat does
not necessarily translate directly to the rear seats. By comparison,
vehicles subject to advanced air bag requirements comply using either
suppression or low-risk deployment for different size child dummies,
including the 6-year-old child dummy, in the front outboard passenger
seat. Vehicles with a suppression system use some type of occupant
detection technology in addition to other inputs (e.g., seat belt use,
seat position, etc.) to determine whether or not to deploy the air bag.
Vehicles using low-risk deployment, however, do not necessarily need to
use occupant detection to meet the advanced air bag requirements for
that option. The vast majority of vehicles use the suppression option
in the front outboard passenger

[[Page 405]]

seat for at least one child dummy, and therefore use occupant
detection.77 78
---------------------------------------------------------------------------

\77\ There is also an option to use a dynamic automatic
suppression system. To date, no manufacturer has attempted to
certify using this option.
\78\ With respect to the driver's seat, while it is subject to
certain advanced air bag requirements, those particular requirements
do not necessitate occupant detection.
---------------------------------------------------------------------------

Vehicle manufacturers that opt to use a rear seat belt warning
system with occupant detection will have to develop and implement
occupant detection solutions that work for the unique seat designs and
configurations found in rear seats (e.g., bench seats, folding seats,
different types of seat cushions, etc.) and validate the performance to
ensure that they meet the new requirements and mitigate the potential
for false positives. Among other challenges, rear seats create more
potential for false positives than the front seats. As we explained in
the NPRM and ANPRM, while occupant detection can reduce false warnings
for unoccupied seats, it can also result in false warnings, due to the
limitations of the sensors and different use scenarios in the rear
seats (e.g., transportation of cargo and pets). In addition, rear seats
may be less well-defined than front seats (most rear seat rows, unlike
the front seat rows, are comprised of three closely spaced seating
positions), which could impede accurate detection. This deficiency
could negatively affect consumer acceptance and/or effectiveness.
Another reason the final rule does not require occupant detection
is that it adds non-trivial costs to the seat belt warning system.
While we agree with Consumer Reports that rear-seat occupant detection
is not prohibitively expensive in the sense that this is true for some
vehicle lines, our cost-benefit analysis shows that occupant detection
would be cost-beneficial only if rear seat belt use increased
substantially more than we estimate it would for a warning system
without occupant detection. Our teardown analysis indicates that
occupant detection components cost $39.74 per vehicle, which, added to
the $19.59 per vehicle cost of the buckle sensor, results in a combined
warning system cost of $59.33 per vehicle (2020 $). We estimate that
the total new fleet cost of a rear seat belt warning system with
occupant detection would be about $802 million (2020 $). With respect
to benefits, there is uncertainty with respect to how much more
effective systems with occupant detection are compared to systems
without it. Because of this uncertainty, our regulatory analysis does
not attempt to estimate the net benefits or cost-effectiveness of rear
seat belt reminder systems that use an occupant detection system. The
regulatory analysis does, however, include a break-even analysis for a
rear seat belt reminder system that requires occupant detection. For
benefits and costs to break even (be equal) for this regulatory option,
seat belt use for rear seat occupants 11 years and older would need to
increase by approximately 5.2 percent when discounted at 3 percent and
6.4 percent when discounted at 7 percent. Furthermore, NHTSA considered
the increase in seat belt use for rear seat occupants that would be
required to match the net benefits under the final rule, which does not
require occupant detection. When discounted at three and seven percent,
seat belt use for rear seat occupants 11 years and older would need to
increase by 6.43 percent to 8.57 percent to match the net benefits
(taking into account the Low and High estimates) under the final rule.
This is about two to three times greater than that estimated for the
compliance option without occupant detection. (For more details, see
Section VIII.B.1 and the FRIA.) Accordingly, while we agree with the
commenters who supported a requirement for occupant detection because
there may be benefits to having occupant detection (such as
facilitating enhanced or more effective warnings) \79\ and would expect
some potential increase in seat belt use from that specific
functionality, an effectiveness increase of this order of magnitude
seems unlikely. Therefore, we do not expect this regulatory alternative
to be net beneficial and would not generate the same level of net
benefits as the final rule. Manufacturers may voluntarily equip
vehicles with occupant detection if they so choose. Our hope is that
over time, as the systems evolve and penetrate the fleet, the
technology will mature and per-unit costs will decrease.
---------------------------------------------------------------------------

\79\ With respect to SKW's comments about the benefits of
monitoring children in forward- or rear-facing CRSs, as we explained
in the NPRM, children restrained by child restraint systems are not
part of the target population for this rule.
---------------------------------------------------------------------------

With respect to the comment from Mr. Paradise concerning what he
believed was an inconsistency between NHTSA's statements that a single-
digit percentage of vehicles with rear-seat occupant detection being a
small percentage of the fleet, and weighing in favor of not requiring
it, and a single-digit percentage of vehicles with an indefinite
reminder being non-trivial and supporting our proposal to require an
indefinite reminder for the front seat belt start-of-trip warning, we
do not believe these statements are inconsistent. In the context of
occupant detection, we are referring to technological feasibility and
likely regulatory cost; in the front seat belt warning section, we are
referring solely to the optimum duration, as there is no question about
feasibility. That is, a single-digit percentage has a different meaning
in the two contexts.
Because we have decided not to require occupant detection, we
disagreed with commenters who recommended requiring one or both of the
proposed options that required occupant detection (full-status with
occupant detection or negative-only with occupant detection). We
continue to believe, as we explained in the NPRM, that while the full-
status system (with occupant detection) does provide the driver with
the most information, the other allowable types of systems, including
those without occupant detection, will provide the driver with
sufficient information to easily determine whether and where there are
any unbuckled occupants and request that they fasten their seat belts.
Accordingly, the final rule allows the proposed positive-only
option. These systems, while not providing information on the occupancy
status of each seat, do provide information on which seat belts are
buckled. The driver can combine this information with knowledge of the
other occupants in the vehicle and determine if there are any unbuckled
occupants and request them to fasten their belts. While this does
require mental work on the part of the driver, and may not be as
effective as a full-status system, we believe it is not so burdensome
as to render such systems ineffectual to such a degree that we see a
basis for prohibiting them. While such systems are not permitted under
ECE R16 or Euro NCAP, manufacturers could select another type of system
if they wished to harmonize with those protocols. (The positive-only
system without occupant detection does conform with the IIHS protocol.)
With respect to Honda's comment that the proposed positive-only option
could potentially leave the driver unaware that the vehicle was
equipped with a seat belt reminder system, we acknowledge that is a
possibility, but it would not be a long-term problem. This would be
limited to times when a driver is driving a vehicle new to them (unless
the driver always reads owner's manuals first) and would only be an
issue until a rear passenger buckles up. Once a rear passenger buckles
up the driver would become aware of the existence of the warning.
We have modified the proposal so that the final rule does not
dictate

[[Page 406]]

specific compliance options for the information conveyed by the visual
warning; the finalized requirements for the visual warning allow all of
the systems that would have been allowed under the proposed rule, as
well as additional systems that would not have been allowed under the
proposal, such as a negative-only system without occupant detection,
and a full-status system without occupant detection. Both the negative-
only system without occupant detection and the full-status system
without occupant detection are consistent with ECE R16 and the IIHS
protocol (they would not be eligible for points under Euro NCAP). One
factor underlying this choice is the lack of firm research data that
could lead NHTSA to meaningfully compare the effectiveness of the
different types of systems,\80\ coupled with the fact that rear seat
belt reminder systems conforming to the finalized requirements have
already been deployed on vehicles sold in the United States.\81\ These
factors make us reluctant to prohibit particular design choices and
inhibit manufacturer flexibility and ability to optimize system
characteristics. We believe that the finalized regulatory text (``A
visual warning indicating how many or which rear seat belts are in use
and/or not in use must activate when the ignition switch is placed in
the `on' or `start' position (or upon manual activation of the
propulsion system, but prior to the vehicle being placed in ``possible
active driving mode'' as defined by FMVSS No. 305))'' \82\ includes all
of the systems manufacturers are currently deploying, but is specific
enough to be objective and enforceable. For example, if there is one
rear occupant, and that occupant is belted, a positive-only system
without occupant detection that accurately indicates one buckled rear
belt, and a full-status system with occupant detection that accurately
indicates one rear occupant with a fastened belt, would both comply
with the finalized regulatory text.
---------------------------------------------------------------------------

\80\ See Mark Freedman et al., Effectiveness and Acceptance of
Enhanced Seat Belt Reminder Systems: Characteristics of Optimal
Reminder Systems Final Report. DOT HS 811 097 at pg. 49 (Feb. 2009)
(hereinafter ``DOT 2009 Seat Belt Study'').
\81\ An exception is a positive-only system with occupant
detection, which is not prohibited by the finalized requirements and
has yet to be deployed on vehicles sold in the United States.
However, we believe it would be unlikely that a manufacturer would
deploy such a system because the presence of occupant detection
allows for more informative reminders--for example, a full-status
reminder--than provided by a positive-only system. This is reflected
in the fact that while we are aware of production versions of
positive-only systems without occupant detection, negative-only and
full-status systems with and without occupant detection, we are not
aware of any vehicle equipped with both occupant detection and a
positive-only reminder system.
\82\ The language relating to EVs is discussed in Section
VI.C.1.
---------------------------------------------------------------------------

We agree with Toyota and Honda that the negative-only system
requires the same cognitive effort on the part of the driver as the
proposed positive-only option, and that it would still be effective and
beneficial, even without occupant detection. We no longer agree with
the view we expressed in the NPRM that such a signal is a false
positive that might either desensitize the driver to the warning signal
or lead them to circumvent or defeat the system. We now agree with
Toyota that this is instead more accurately considered relevant
information on seat belt status that the driver can use to determine
whether there are any unbuckled occupants and request them to fasten
their seat belts.
We reached a similar conclusion with respect to full-status systems
without occupant detection. As we discussed above for the negative-only
systems without occupant detection, we agree that while this system
does not provide as much information as would a system with occupant
detection, the information it does provide on the seat belt status at
every seating position (occupied or not) is useful information for the
driver. We also agree with the commenters who argued that allowing this
option would support the introduction of systems that are already in
widespread use, without adding in additional cost and complexity.
ii. Lack of an Audible Warning
The NPRM recognized that warnings with an audible component are
generally more effective than visual-only warnings. However, we also
recognized that requiring an audio-visual warning would necessitate
requiring occupant detection because, without occupant detection, an
audible warning would activate every time a rear seat is empty. These
``false positives'' would annoy the driver (as well as other occupants)
and would decrease the effectiveness of the warning. Thus, the NPRM did
not propose an audible warning on start-up. However, manufacturers
would be free to provide an audible warning on start-up if they so
choose. This approach is also consistent with ECE R16, Euro NCAP, and
IIHS.
Comments
Many of the commenters who supported requiring occupant detection
also supported requiring an audible warning (NSC, Consumer Reports,
SRN, Karleigh Cross, and an anonymous commenter). SRN, Consumer
Reports, and Ms. Cross commented that audible warnings are more
effective than visual-only warnings. Consumer Reports also commented
that requiring an audible component to the rear seat start-up warning
would also make start-up warnings more consistent throughout a vehicle,
regardless of the seating position.
Agency Response
The final rule does not require a rear seat audible start-of-trip
warning, for the reasons articulated in the proposal. Because the final
rule does not require occupant detection in the rear seats, it does not
require an audible warning. We acknowledge that audio-visual warnings
are more effective than visual warnings alone, and we believe that
consumers would accept them. However, we believe that a visual warning
alone will still be effective. While we cannot precisely estimate
effectiveness, we have used a three to five percent belt use rate
increase range (``lower'' and ``higher'' scenario) in our analysis
based on the available research. This analysis is explained in detail
in the FRIA. We agree that in general, consistency between the rear
reminder and front reminder requirements (which do require an audio-
visual start-of-trip warning) is desirable, but do not believe that not
requiring an audible component to the rear start-of-trip warning will
create an issue in practice. In this context, the relevant potential
concern with this inconsistency is that the driver--the recipient of
the warning--would be confused or annoyed by any differences in the two
warnings. Ultimately, we do not believe this inconsistency is a
significant problem. The front seat belt warnings have been in vehicles
for many years. Rear seat belt warnings will be new to most drivers, so
drivers will have to become accustomed to them. In addition, the rear
reminder will be a fairly prominent visual warning. If the driver is
unsure of how the warnings operate, this rule also requires that the
owner's manual include an accurate and easily understandable
description of system features and operation.
iii. Triggering Conditions for Start-of-Trip Warning (Not Including
Occupant Detection Criteria)
The NPRM proposed that the rear seat start-of-trip warning (which,
as discussed above, is only required to be a visual warning) activate
when the ignition switch is placed in the ``on'' or ``start'' position,
except for negative-only systems when there are no occupied rear seats
with a seat belt not

[[Page 407]]

in use (for which we proposed that a warning not be required to
activate). The activation criteria were modeled on the existing driver
seat belt warning requirements and are also similar to those in ECE
R16, Euro NCAP, and the IIHS protocol.
ECE R16 requires that the rear seat belt visual warning activate
when a belt is not fastened and the ignition or master control switch
activated.\83\ It also provides that for vehicles with rear seat
occupant detection, the visual signal does not need to indicate
unfastened belts at unoccupied seats.\84\
---------------------------------------------------------------------------

\83\ Section 8.4.2.3.1.
\84\ Section 8.4.4.2.
---------------------------------------------------------------------------

Euro NCAP similarly requires that the warning ```start' at the
commencement of each `journey' that the vehicle makes.'' \85\ More
specifically, the Euro NCAP protocol specifies that the visual signal
be activated ``when the ignition switch is engaged (engine running or
not) and a seatbelt is not fastened.'' \86\ However, Euro NCAP allows
for short breaks in the journey (up to 30 seconds) to account for
events such as engine stalling where the reminder is not required to
start again.\87\ Euro NCAP also provides that for systems with rear
seat occupant detection, the visual signal does not need to indicate
the number of rear seat belts in use or not in use.\88\
---------------------------------------------------------------------------

\85\ Section 3.4.1.
\86\ Section 3.4.2.1 (front); Sec. 3.4.3.1.1 (rear).
\87\ Section 3.4.1.
\88\ Section 3.4.3.1.3.
---------------------------------------------------------------------------

For the rear seats, the IIHS protocol permits a 10-second delay
between the ignition being turned on and the activation of the visual
signal. Similar to ECE R16 and Euro NCAP, no visual signal is required
for the rear seat belts if there are no unfastened belts at occupied
seats.
The major differences between the proposal and other approaches
were that, unlike ECE R16, we did not propose to refer to a ``master
control switch'' because we did not believe it is necessary to
introduce this new term into FMVSS No. 208; unlike Euro NCAP we
proposed not allowing for short breaks in the journey; and unlike IIHS
we did not propose allowing any delay after the ignition was turned on.
Comments
Commenters differed on whether the start-of-trip warning should be
permitted to be delayed. HATCI and Ford supported the proposed trigger
conditions (which did not permit a delay). On the other hand, Auto
Innovators, NADA, Freedman, and Nissan recommended allowing a delay.
Nissan, Auto Innovators, and NADA recommended aligning with the IIHS
protocol and permitting a 10-second delay, while Freedman favored a 30-
second delay. Auto Innovators also commented that while it generally
supports the agency harmonizing with ECE R16, the agency should
maintain flexibility for when these warnings are displayed on startup
and allow for a brief delay for when the alert is provided. Freedman
also commented that certain systems, such as an electronic system
separate from that of the OEM system, will require a powerup and boot
cycle which can take several seconds.
Auto Innovators also requested that the final rule allow the visual
warning to be suppressed if all rear row seating positions are belted
or determined to be empty based on occupant detection.
Lastly, RVIA explained that motor homes can be used in many ways
other than for transportation, such that the ignition may be turned on
with occupants seated in the rear accessing the vehicle's amenities,
but with no intention of placing the vehicle in motion. RVIA was
concerned that such use of the rear seats would trigger the rear seat
belt visual warning, even though the motor homeowner has no intention
of operating the vehicle. RVIA concluded that a visual warning system
on vehicle start-up would often go unnoticed in this scenario, creating
a requirement not suitable for the application of the start-up trigger
in a motor home.
Agency Response
The final rule adopts the proposal for the warning to activate on
start-up, with no provision for a delay. We continue to believe that
basing the trigger on the ignition switch is preferable to delaying the
warning until the vehicle is placed in gear because with a delay, there
could be instances where a driver would pull out onto the road before
the warning starts and before passengers have belted. The finalized
requirements increase the likelihood that the occupants fasten their
belts before the vehicle is in motion.\89\ With respect to mitigating
interaction with other vehicle warnings, NHTSA does not believe this
will be an issue at vehicle start-up because critical safety warnings
that activate at start-up would likely have dedicated space on the
display. Interactions between warnings is discussed in more detail in
Section VI.C.4. We believe consumers will accept this start-up warning.
The longstanding current front seat belt warning is based on similar
triggers and has not caused any issues. In addition, the rear start-of-
trip warning is visual-only, so any potential annoyance is minimized.
This factor distinguishes the rear-seat warning from the front seat
belt warning, which we are requiring to be both audio-visual and to
have two phases. We acknowledge there may be some scenarios during a
trip where a rear seat belt warning is not required for an unbuckled
occupant; for example, a passenger pickup scenario when the car is not
turned off. In such a scenario, we are not requiring a warning because
we are not requiring occupant detection, which would be necessary to
detect the new occupant (and potentially avoid a false warning).
Manufacturers of vehicles with rear-seat occupant detection may choose
to provide warnings for such situations.
---------------------------------------------------------------------------

\89\ See DOT 2009 Seat Belt Study at pg. 65.
---------------------------------------------------------------------------

In addition, we are modifying the proposed trigger condition
related to the vehicle ignition being in the ``on'' or ``start''
position for both the front and rear seat belt warning to better
account for EVs. This change is discussed in Section VI.C.1. This
modification generally harmonizes with ECE R16, Euro NCAP, and the IIHS
protocol, so that a vehicle that complies with the finalized trigger
requirements can still meet these requirements; some exceptions are
discussed immediately below.
In addition, we have also modified the proposal so that the final
rule does not require a visual warning in three circumstances: (1) for
an unoccupied seat if the system is able to determine whether a seat is
occupied; (2) for a seat belt that is in use in a system designed to
indicate to the driver how many or which rear seat belts are not in
use; and (3) for a seat belt that is not in use in a system designed to
indicate to the driver how many or which rear seat belts are in use.
This regulatory text is intended to clarify two things.
First, that, depending on the type of seat belt reminder system and
belt use/occupancy scenario, a visual signal may not be necessary for a
particular DSP, or may not be necessary for any DSP. So, for example,
no visual warning would be required for a negative-only system when
every rear seat is occupied by a belted occupant. Another example: if
no rear seats are occupied, no visual signal is required for negative-
only, positive-only, or full-status systems with occupant detection; a
visual warning would, however, be required in this case for a negative-
only system without occupant detection (assuming that no rear belts
were in use) and a full-status system without occupant detection.

[[Page 408]]

This requirement is consistent with ECE R16, Euro NCAP, and IIHS.
Second, this also clarifies, in response to the comments, that
systems utilizing symbols or numbers may utilize colors other than
green or red to indicate unoccupied seats or seating positions for
which the system is not providing information on belt use. Accordingly,
a negative-only system would be permitted to display a pictogram that
denotes a seating position with an in-use belt as grayed-out (to give
one example).\90\
---------------------------------------------------------------------------

\90\ See also Section VI.C.3, Visual Warning Characteristics.
---------------------------------------------------------------------------

Freedman's comment regarding certain vehicles requiring more time
to boot up appears to be referring to accommodating aftermarket
systems. Because the final requirements apply to vehicles before first
purchase other than for resale, they do not directly apply to
aftermarket systems that are installed later on. However, Sec. 30122
of the Safety Act prohibits a vehicle modifier from taking a vehicle
out of compliance with an applicable FMVSS.\91\ (The vehicle owner is
not subject to the make inoperative provision). Therefore, a vehicle
modification performed after the compliance date of this final rule on
a vehicle with a rear seat belt warning system certified to the
requirements in this rule that modifies the vehicle such that the rear
seat belt visual warning does not activate when the ignition is in the
``on'' or ``start'' position (or upon manual activation of the
propulsion system, but prior to the vehicle being placed in ``possible
active driving mode'' as defined by FMVSS No. 305) \92\ would violate
Sec. 30122 and would therefore not be permitted.
---------------------------------------------------------------------------

\91\ 49 U.S.C. 30122(b) (``A manufacturer, distributor, dealer,
rental company, or motor vehicle repair business may not knowingly
make inoperative any part of a device or element of design installed
on or in a motor vehicle or motor vehicle equipment in compliance
with an applicable motor vehicle safety standard prescribed under
this chapter unless the manufacturer, distributor, dealer, rental
company, or repair business reasonably believes the vehicle or
equipment will not be used (except for testing or a similar purpose
during maintenance or repair) when the device or element is
inoperative.''); section 30122(a) (``(a) Definition. In this
section, ``motor vehicle repair business'' means a person holding
itself out to the public to repair for compensation a motor vehicle
or motor vehicle equipment.'').
\92\ See Section VI.C.1.
---------------------------------------------------------------------------

The final rule does not incorporate RVIA's request to accommodate
use scenarios specific to Recreational Vehicles (RVs). We agree that in
the scenarios identified by RVIA the warning would activate when the
vehicle was turned on with no intent to drive (thus obviating the need
for a seat belt). A speed or motion trigger could address this issue,
but we believe that such a trigger is undesirable because there is a
safety benefit to having occupants belted before the vehicle is in
motion or when it is travelling at lower speeds. Moreover, because the
rear seat belt start-of-trip warning is visual-only, there are not the
same consumer acceptance concerns that led us to include a speed
criterion like we have included for the second-phase front seat belt
audible warning. (See Section VI.B.3.) We could also potentially
address this concern by either exempting RVs or crafting trigger
criteria specific to RVs. We conclude the former is undesirable due to
the significant safety benefit of belts when the vehicle is in motion,
and that the latter would be overly complex. In addition, the rear seat
belt start-of-trip warning is a mild visual warning that should not
cause meaningful consumer annoyance (or condition them to ignore the
warning) in these use cases.
iv. Seat Occupancy Criteria and Interaction With Child Restraint
Systems
For rear seat belt warning systems that manufacturers voluntarily
choose to equip with occupant detection, NHTSA proposed the occupancy
criteria for the test dummy (or human, at the manufacturer's option)
that NHTSA would position in the seat to conduct compliance testing of
the system. NHTSA proposed that a rear designated seating position
would be considered ``occupied'' when an occupant who weighs at least
46.5 lb (21 kg), and is at least 45 in (114 cm) tall, is seated there.
These criteria are proxies for a 6-year-old child, which roughly
corresponds to a typical age at which a child would begin using a seat
belt (with a booster seat), transitioning from a forward-facing child
restraint system (CRS). These are the same criteria used in FMVSS No.
208 to specify the smallest child that may be used as an alternative to
the 6-year-old dummy in static suppression tests under FMVSS No. 208.
We proposed using either a human being, at the manufacturer's option,
or any anthropomorphic test device specified in 49 CFR part 572 that
meets these proposed weight and height criteria (Section VI.C.8., Test
Procedures).
The proposed criteria corresponded to a smaller occupant than ECE
R16 or Euro NCAP, each of which essentially specifies an occupant (or
load) no smaller than a 5th percentile adult female (e.g., the HIII-5F
specified in 49 CFR part 572). In the NPRM we explained that we
believed that harmonizing with ECE R16 and using a heavier dummy would
not capture the child segment of the population that could be
restrained with a seat belt. We also did not believe it was necessary
to use a larger-size occupant because a system capable of recognizing a
6-year-old should also be capable of recognizing larger occupants.
At the same time, we tentatively believed that the proposed
criteria were preferable to criteria reflecting a younger occupant
(lower weight). The smallest dummy that would meet the proposed weight
and height criteria is the 6-year-old dummy specified in part 572. The
next smallest dummy represents a 3-year-old child (i.e., the Hybrid III
3-year-old); we believed it would not be appropriate to specify the use
of the 3-year-old because a child represented by this dummy should be
seated in a forward- or rear-facing CRS, not restrained with a seat
belt.
NHTSA did not propose to require any sort of CRS detection
capabilities. As explained in the NPRM, there are essentially three
types of CRSs: rear-facing CRSs, forward-facing CRSs, and booster
seats. Rear-facing and forward-facing CRSs are child seats that are
installed using either Lower Anchors and Tethers for Children (LATCH)
or a seat belt to secure it in place. Booster seats raise and position
a child so the vehicle's lap-and-shoulder belt fits properly. We
tentatively believed that a forward- or rear-facing CRS installed with
the seat belt would not cause problematic false warnings; rather the
system would just register the CRS as a buckled passenger. Similarly,
we believed that a forward- or rear-facing CRS installed with LATCH
would not pose issues necessitating any specific requirements related
to the LATCH system, such as LATCH sensors.
We also did not believe a booster seat would present any special
challenges to a seat belt warning system. If an unbelted child is in a
booster seat, the system would register the belt as not fastened and,
if equipped with occupant detection, that the seat was occupied. The
system would not have to specifically detect the booster seat because
the performance criteria are weight-based. In addition, we would not
expect an occupant detection system to provide a false warning for an
unoccupied booster seat because the proposed seat occupancy criterion
(roughly equivalent to a 6-year-old) is heavier than an unoccupied
booster seat. We did not propose to specify the use of a booster seat
for testing because children may be prematurely transitioned to a seat
belt without the use of a booster, and we believe it is desirable to
test the lower end of the

[[Page 409]]

possible weight range that encompasses children that could conceivably
be restrained with a seat belt.
Comments
A number of commenters (Auto Innovators, Mercedes, GM, NADA, IEE,
Honda, HATCI, and Consumer Reports) disagreed with the proposal and
recommended harmonizing with ECE R16 and Euro NCAP and specifying
occupancy criteria based on a 5th-percentile adult female occupant.
These commenters made a variety of arguments.
Auto Innovators commented that harmonizing with the ECE
requirements would avoid introducing unnecessary complexity and reduce
the need for additional lead time to develop U.S.-specific designs. IEE
commented that the proposed detection criterion would entail
significant additional costs.
IEE also commented that a detection criterion based on the 5th
percentile female would address the key target population of unbelted
teenagers and adults. Relatedly, IEE noted that the NPRM analysis
investigated potential benefits for the age group 6 to 10 years old and
only found a very small belt usage increase (by only 0.27 percent to
0.41 percent) and concluded that members of this age group already have
high rates of seat belt use (98 percent according to the preliminary
regulatory impact analysis).
Consumer Reports, IEE, Auto Innovators, Honda, HATCI, NADA, RVIA,
and GM raised concerns regarding feasibility. Consumer Reports agreed
with NHTSA on the importance of testing the lower end of the possible
weight range that encompasses children that could conceivably be
restrained with a seat belt alone, but believed that it would be
premature to require the detection of dummies smaller than the 5th
percentile adult female because the ability to detect occupants smaller
than the 5th percentile adult female is limited. IEE commented that
while detecting a 5th percentile female is well-established in the
market and would not present any design or technical challenges, it was
not aware of any car on the market that would be able to meet the
proposed detection of the 6-year-old child scenarios, with or without a
booster cushion. IEE commented that the 5th percentile female is the
state-of-the art in contemporary sensing technology for seat belt
reminder-related occupant detection and that no realistic alternative
technologies are readily available at comparably low costs. IEE stated
that it believed that the 7 percent of U.S. MY 2022 vehicles with rear
seat occupant detection all meet the 5th percentile female detection
criterion, not the one 6-year-old proposed in the NPRM.
IEE also commented that the proposal assumed that a 6-year-old
child on the booster seat would be automatically covered and detected
as it has a higher total weight than the weight proposed for the
occupancy criteria. IEE stated that this assumption is wrong: rear
occupant detection systems are designed to detect a load that is
generating a pressure profile on the seat foam that matches the
pressure profile of a human buttocks. IEE commented that the pressure
profile generated by a booster seat is different and would not be
classified by the system as an occupant; contemporary occupant
detection sensors used for seat belt reminder systems are not designed
to detect booster seats, and child seats are considered as non-
detection objects. IEE indicated that this distinction is also required
to differentiate between humans and objects, to avoid objects that
would be likely to trigger false positives. Auto Innovators similarly
commented that the contact area between a booster seat and a seat
cushion can vary, causing some of the occupant's weight to be
distributed to the seat itself or to the LATCH system, rather than to
the weight sensor.
Auto Innovators also pointed out that child occupants are also more
likely to be out-of-position compared to an adult, further contributing
to uneven weight transfer. Auto Innovators argued that if the weight of
a child in a booster seat is not transferred to the weight sensor, the
proposed system could misclassify the seat as empty. If this
misclassification occurs, coupled with the lack of a visual warning for
an unfastened seat belt at an unoccupied seat, Auto Innovators argued
there would be no visual warning for cases where an age-appropriate
child is sitting in a booster seat and not wearing a belt. Relatedly,
IEE commented that more advanced detection technologies (such as
cameras or radar sensors) are not currently used in the context of a
seat belt reminder function, and that these technologies would still
have to prove their reliability and robustness for the occupant
detection needs of a seat belt reminder system. IEE explained that
while future developments may enable the support of seat belt reminder
functionalities with these technologies, it is too early to consider
such a potential innovation in a regulatory pass/fail scenario.
Honda, HATCI, Auto Innovators, NADA, IEE, RVIA, Honda, and GM
commented that specifying criteria matching a 6-year-old would
exacerbate the problem of false positives. HATCI and IEE commented that
behavioral alternatives to avoid false positives, such as moving cargo
to the floor of the vehicle or buckling the belt before loading heavy
cargo onto seats, may not always be feasible or reliable. Auto
Innovators and Honda argued that the proposed criteria would
potentially discourage manufacturers from implementing occupant
detection systems due to the potential for false warnings.
IEE similarly commented that if the agency were to adopt the 6-
year-old criterion proposed in the NPRM, manufacturers would be
disincentivized from implementing occupant detection in rear seats. IEE
explained that because the proposed detection threshold is not
technically feasible today within a regulatory pass/fail context, the
threshold proposed in the NPRM would fail advanced rear seat belt
reminder systems that have already entered the U.S. market and that
offer a seat belt warning functionality that exceeds the proposed legal
minimum. IEE stated that this requirement would force vehicle
manufacturers to withdraw these advanced seat belt reminder systems
from the market and downgrade the seat belt reminder systems features
to the legal minimum (the positive-only compliance option). IEE argued
that this result would be counterproductive from a safety perspective.
IEE and Consumer Reports commented that manufacturers could
voluntarily detect occupants smaller than the 5th percentile female.
IEE argued that making such detection voluntary would provide
flexibility for innovation. Consumer Reports recommended that NHTSA
incorporate detection of dummies smaller than the 5th percentile female
into NCAP ratings for rear seat belt reminders, which would award
manufacturers for going above and beyond the regulatory minimum and
drive innovation.
On the other hand, NSC and SRN suggested a 3-year-old child for the
occupancy criterion. NSC commented that data from the National Digital
Car Seat Check Form show that many children are not riding in the
appropriate CRS based on their height and weight, so specifying
criteria corresponding to a 3-year-old child would protect children.
SRN similarly noted that the weight of a 3-year-old dummy, though
average for a toddler, is also the weight of many older children in the
lower growth chart percentiles. SRN argued that since nearly all
school-age children ride in seat belts or boosters (including these
lighter-weight

[[Page 410]]

children, regardless of NHTSA best-practice recommendations), families
would benefit from warnings about the belt-use status of those
children. SRN explained that this is especially true for warnings that
a passenger has unbuckled during a ride, which younger, less mature
children may be prone to do. SRN explained that, as proposed, a system
with occupant detection would not recognize some of the youngest
booster/belt users, may provide inadequate warnings to families, and
may cause caregivers some frustration in interpreting status
indicators. SRN also commented that in comments to the ANPRM, SRN had
voiced the concern that LATCH-installed car seats could trigger false
alarms. SRN was less concerned that the proposed system will rise to
the level of nuisance and is more concerned that false warnings will
happen, such as when relatively heavy car seats are installed using
LATCH. SRN argued that owners will need clear guidance in owner's
manuals on how to interpret warnings when traveling with children, and
that these instructions should be included (or at least referenced) in
the child passenger section of the manual.
Consumer Reports, HATCI, and Freedman agreed with NHTSA that a CRS
detection requirement was not necessary. Consumer Reports stated that
consumers might be better served by incorporating CRS detection into a
component of NCAP for rear seat belt reminder systems to help drive
safety innovation. Freedman commented that the easiest and most
effective solution for LATCH-installed CRS is to continue recommending
the seat belt be fastened behind the CRS.
Auto Innovators and GM recommended that NHTSA ensure a technology-
neutral approach that includes consideration of compliance options that
permit the use of camera- or vision-based sensors, or other
technologies that may be adopted in lieu of weight-based sensors, as a
means for determining occupant presence at a given designated seating
position. Advocates and Public Citizen commented that the final rule
should not preclude or discourage the use of existing state-of-the-art
technology.
Agency Response
After considering the comments, NHTSA has decided to adopt the
proposal to use (at the option of the manufacturer) either a
anthropomorphic test device at least as large as a 49 CFR part 572,
subpart N 6-year-old child dummy or a person, at the manufacturer's
option, that is at least 21 kg in weight and 114 cm in height to define
an occupied rear designated seating position for the purposes of
testing the rear seat belt reminder system. These criteria represent a
50th percentile 6-year-old child, and only specify the low end of the
occupancy criteria used for compliance testing. Therefore, when we
refer to a 6-year-old as our occupancy criteria, this includes
occupants or dummies that are larger.
Before addressing the specific issues raised by the commenters, it
is important to recognize that this final rule does not require or
necessitate occupant detection. Moreover, we recognize that a
manufacturer currently deploying reminder systems with occupant
detection based on the 5th percentile female would likely need some
time and effort to develop and implement new sensor solutions in the
rear. Based on MY 2022 NCAP data, approximately 7 percent of vehicles
sold in the U.S. are equipped with rear seat belt reminders using
occupant detection. The commenters, however, did not provide specific
information on what additional development would be necessary to meet
the requirements when tested with a 6-year-old.
Further, as explained above (Section VI.A.2.a.i) we have revised
the proposed requirements to provide greater flexibility for systems
without occupant detection. The proposal only included one compliance
option (the positive-only compliance option) without occupant
detection. In response to the comments, the final rule would allow for
additional warning systems without occupant detection (e.g., negative-
only and full-status). Given this flexibility, manufacturers can simply
use reminder systems without occupant detection if they believe they
cannot deploy a reminder system using occupant detection that would
comply with the requirements when tested with a 6-year-old.
Given the above, NHTSA has concluded that it would fulfill the MAP-
21 mandate, meet the need for safety, and be practicable and
appropriate to require that an occupant detection system be capable of
detecting at least a 6-year-old. There are several reasons for this
decision.
First, section 31503 of MAP-21 directs NHTSA to initiate (and
finalize, if the Sec. 30111 criteria are met) a rulemaking proceeding
``to provide a safety belt use warning system for designated seating
positions in the rear seat.'' Section 31503 itself does not refer to
particular classes of occupants or identify a target population.
``Subtitle E--Child Safety Standards'', in which Sec. 31503 is
located, however, contains four mandates related to child passenger
safety: improving the protection seated in CRSs during side impact
crashes; improving the ease of use for LATCH systems; providing seat
belt reminders for rear seats; and researching the risk of hyper- or
hypothermia to children or other unattended passengers in rear seating
positions.93 94
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\93\ See, e.g., Norman J. Singer & Shambie Singer, 2b Sutherland
Statutory Construction section 46:5 (7th ed.) (``[E]ach part or
section of a statute should be construed in connection with every
other part or section to produce a harmonious whole. Thus, it is not
proper to confine interpretation to the one section to be
construed.''); section 47:3 (explaining that while legislative
titles cannot control a statute's plain words they ``may help
resolve uncertainty'' and ``illuminat[e] statutory meaning''). See
also id. section 47:6 (``Courts give effect to all the language of a
purview as a harmonious whole, in light of the statute's purpose,
and regardless of sectional formatting, unless to do so is plainly
contrary to legislative intent.'').
\94\ MAP-21, Division C, Title I, ``MOTOR VEHICLE AND HIGHWAY
SAFETY IMPROVEMENT ACT OF 2012.''
---------------------------------------------------------------------------

In addition, the Safety Act gives NHTSA the discretionary authority
to issue safety standards to address specific safety needs, provided
that the standard is objective, practicable, and appropriate for the
type(s) of vehicles to which it applies.\95\ NHTSA has concluded that
requiring a rear seat belt warning system equipped with occupant
detection be able to detect unbelted children smaller than the size
represented by the 5th percentile female crash test dummy meets a
safety need and is practicable and appropriate.
---------------------------------------------------------------------------

\95\ 49 U.S.C. 30111.
---------------------------------------------------------------------------

Specifying occupant characteristics corresponding to a 5th
percentile female would not address rear seat belt usage by children
because the vast majority of children are smaller than the 5th
percentile female test dummy. The population of children seated in the
rear who should be restrained with a seat belt is comprised of children
seated in a booster seat and children who have transitioned out of a
booster seat to sit directly on the vehicle seat. As we explained in
the NPRM, children typically begin sitting in a booster seat
(transitioning out of a forward-facing CRS) around 4-7 years old
(depending on the height and weight of the child and the respective
limits of their forward-facing car seat). Children typically transition
out of a booster seat between the ages of about eight and thirteen
(again, exactly when depends on the child's height and weight). The
Hybrid III 5th percentile female crash test dummy weighs 108 lb (50
kg). This weight corresponds (approximately) to a 50th percentile
fourteen-year-old girl and a 50th percentile thirteen-and-a-half-year-
old boy.\96\ This means that if

[[Page 411]]

NHTSA were to specify criteria matching the 5th percentile female, it
would essentially be ignoring a large percentage of children ages 6-14,
and likely some 15-18 year old children with weight lower than that of
a 5th percentile female. That is, if NHTSA specified the 5th percentile
female, the rear seat belt warning requirements would only be targeting
older children, not younger children.\97\ This disparity strongly
suggests that NHTSA should specify a smaller occupant for testing if
doing so would be practicable.
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\96\ Center for Disease Control Growth Charts for Children 2-20
years of age: Boys Stature-for-age and Weight-for-age percentiles
and Girls Stature-for-age and Weight-for-age percentiles, published
in May 2000 (modified in November 2000) and available at <a href="https://www.cdc.gov/growthcharts/data/set1clinical/cj41c022.pdf">https://www.cdc.gov/growthcharts/data/set1clinical/cj41c022.pdf</a> and <a href="https://www.cdc.gov/growthcharts/data/set1clinical/cj41c021.pdf">https://www.cdc.gov/growthcharts/data/set1clinical/cj41c021.pdf</a>,
respectively. (last accessed September 10, 2024).
\97\ A booster seat augments the total weight on the rear seat.
However, as we explained in the NPRM--and as we adopt in this final
rule--we will not be testing with a booster seat because we are
aware that children can be prematurely transitioned to a seat belt
without the use of a booster, and we believe it is desirable to test
the lower end of the possible weight range that encompasses children
that could conceivably be restrained with a seat belt alone. We
discuss the issue of booster seats in our discussion regarding
feasibility later in this section.
---------------------------------------------------------------------------

Although NHTSA has concluded that specifying occupant
characteristics matching those of a 6-year-old child would meet a
safety need and be fully consistent with MAP-21, MAP-21 directs NHTSA
to issue a final rule only if the rule would meet the criteria set out
in Sec. 30111 of the Safety Act. These criteria include that the rule
be practicable. As noted earlier, the statutory criterion of
practicability is multidimensional (see Section IV. Statutory
Authority). After considering the comments, NHTSA agrees that most
currently deployed rear seat belt warning systems utilizing occupant
detection are not able (or designed) to reliably detect a 6-year-old
occupant. NHTSA also agrees with the commenters who indicated that
there are a number of challenges to rear-seat occupant detection,
related both to false negatives and false positives. However, while
many or most currently deployed rear occupant detection systems used
for seat belt warnings may not comply with the requirements in the
final rule, we believe that OEMs are capable of improving the
technology and meeting these challenges. Further, NHTSA believes that
selecting a 6-year-old child instead of the 5th percentile female
appropriately balances benefits and costs. We explain this conclusion
in more detail below.
NHTSA believes that while current occupant detection systems might
not reliably detect a 6-year-old child, or a booster seat, such a
requirement is feasible. NHTSA acknowledges the commenters who argued
that many or most rear occupant detection systems that are currently
deployed may not be able to reliably detect a 6-year-old occupant,
either seated directly on the seat or in a booster seat. NHTSA has not
tested current systems to verify or refute this claim, so we have no
firm basis on which to agree or disagree with these comments. NHTSA
has, though, noted that some owner's manuals inform consumers that if
they place lightweight objects (such as a briefcase) on the rear seat,
it may trigger the seat belt warning; this suggests that some rear seat
belt occupant detection systems may be capable of detecting younger
(and therefore lighter) occupants. For example, the owner's manual for
the MY 2024 Cadillac Escalade states that ``[t]he rear passenger seat
belt reminder light and chime may come on if an object is put on the
seat such as a briefcase, handbag, grocery bag, laptop, or other
electronic device. To turn off the reminder light and/or chime, remove
the object from the seat or buckle the seat belt.'' \98\ In most cases
the weights of these listed items would be less than the weight of a 6-
year-old. Furthermore, we understand (although again, have not been
able to verify) that at least one manufacturer's system may be able to
detect a 6-year-old not in a booster.\99\
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\98\ Page 114. As another example, the owner's manual for the MY
2024 Tesla Model Y states: ``If all occupants are buckled up and the
[seat belt] reminder stays on, . . . remove any heavy objects (such
as a briefcase) from an unoccupied seat.''
\99\ NHTSA is not disclosing further details about this finding
because this information is confidential.
---------------------------------------------------------------------------

We also acknowledge that some rear-seat occupant detection systems
may not be able to reliably classify a young child seated in a booster
seat as an occupant. We explained in the NPRM that children start using
belts (with a booster seat) at about 6 years old, and typically
transition out of a booster seat around 8 to 13 years old. We
acknowledge, as IEE commented, that some rear detection systems may not
simply classify objects/occupants based on weight, but may also base
the classification on other information, such as the pressure profile,
so that a child seated in a booster seat may not be classified as a
human occupant, regardless of the child's weight and height. We
recognize that manufacturers would have to develop a solution to this
issue. We also acknowledge other issues pointed out by the commenters
that make accurate detection a challenge, such as out-of-position
children.
Nevertheless, we believe that it is feasible to develop this
technology. We agree with IEE that more advanced technologies (such as
radar sensors) are not yet proven. However, occupant detection
technology similar to that used for advanced air bag testing in the
front that is used to detect different sized dummies in different test
scenarios,\100\ including 6-year-old dummies, could potentially be
reprogrammed to address our occupancy criteria needs and this would
also address the comments about not being able to detect children in
boosters. Testing with a 6-year-old should also be compatible with the
requirements in ECE R16 and Euro NCAP; if a system can recognize a 6-
year-old occupant, it should also be able to recognize an occupant with
the characteristics of the 5th percentile female. Moreover, to give
manufacturers flexibility, we have kept the requirements as technology-
neutral as possible in order to facilitate innovation. We acknowledge
that requiring an occupant detection system to meet the final
requirements when tested with a dummy or human representing a 6-year-
old could increase the cost of the system and may take some time to
implement and test, but again, the final rule does not require occupant
detection. We are also providing two years of lead time, so current
occupant detection systems could be offered until then (See Section IX,
Compliance Date).
---------------------------------------------------------------------------

\100\ The Advanced Air Bag rule was targeted at protecting all
individuals from potential harm from air bags; specific requirements
were included that were targeted at protecting children. See Section
VI.A.2.a.1.
---------------------------------------------------------------------------

With respect to the comments on cargo (or pets) leading to false
warnings based on the relatively low weight specification for the
occupancy criteria, while this is a potential issue, we believe that it
is mitigated in a variety of ways. First, potential consumer annoyance
should be mitigated by the relatively short duration of the warning (60
sec) and the fact that it does not have an audible component. The
weight of the types of objects typically placed on the rear seats (such
as briefcases, water bottles, and groceries) would also likely be well
under the weight of a 6-year-old (46.5 lb).
There may also be technical solutions to mitigate false warnings.
Several comments referred to complications with detection related to
the weight of the occupant or object placed on the seat. However,
occupant detection technology reliant solely on weight-based sensors
may not necessarily be the only technology solution to meet the
performance requirements in this final

[[Page 412]]

rule. We also note that, based on the comments alone, it appears that
there are presently issues with false alarms for current systems which
are presumably based on detecting a 5th percentile female occupant.
(However, no specific data were provided on the performance of these
systems with relation to false warnings or how such false warnings have
affected acceptance.)
If technical solutions to mitigating any remaining consumer
acceptance concerns are not readily available, NHTSA continues to
believe the behavioral solutions we suggested in the NPRM (such as
placing objects on the floor instead of the seat, or buckling the belt
if cargo is placed on the seat) are viable. Although Honda and HATCI
did not believe such behavioral solutions were viable, as noted
earlier, at least some manufacturers are already providing such
guidance in the owner's manual. We acknowledge that there may be some
trade-off in effectiveness if consumers frequently buckle the belt when
cargo is placed on the seat or become accustomed to ignoring the
warning. (We are not aware of any data or research on such trade-offs.)
Nevertheless, we believe that this concern would not meaningfully
affect the warning's effectiveness, and that any lessening in
effectiveness should be offset by the system being able to detect the
full range of occupants that should be using a seat belt.
With respect to interactions between the occupant detection system
and CRSs, we agree with the commenters that the final rule should not
require that the occupant detection system be able to detect a forward-
or rear-facing CRS installed with LATCH. We agree with Freedman and
Honda that the easiest and most effective solution to avoid false
warnings for LATCH-installed CRSs is to continue recommending the seat
belt be fastened behind the CRS. We encourage this practice on our
website \101\ and some manufacturers are already providing consumers
with this guidance.\102\
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\101\ See <a href="http://www.nhtsa.gov/road-safety/child-safety">www.nhtsa.gov/road-safety/child-safety</a> (last accessed
May 16, 2024).
\102\ For example, the owner's manual for the MY 2024 Subaru
Forester advises the consumer that ``[t]he seatbelt warning system
of the rear seats detects if any of the seats are occupied by a
passenger. Installing a child restraint system in the rear seating
area, using the LATCH anchors, may result in the activation of the
passenger seatbelt warning light and chime. Fastening the rear
seatbelt prior to installing the child restraint system will avoid
activating the passenger seatbelt warning light and chime.''
---------------------------------------------------------------------------

NHTSA also considered the relative costs and benefits of specifying
a 6-year-old child as opposed to the 5th percentile female. In
particular, we considered some commenters' assertions that specifying
the 6-year-old would discourage manufacturers from adopting systems
with occupant detection or would force manufacturers to downgrade their
systems to the positive-only option (which did not require occupant
detection). We have concluded that specifying a 6-year-old as opposed
to the 5th percentile female appropriately balances costs and benefits.
There are several reasons for this conclusion.
First, and most important, a system that does not monitor child
occupants smaller than a 5th percentile female does not monitor the
entire population of children who can and should be using seat belts.
As we noted above, the height and weight of the 5th percentile female
dummy correspond, approximately, to that of a 14-year-old. Because the
5th percentile female dummy would not represent most younger children,
the system would not work accurately for these children. This is
especially worrisome given that children 12 years old and younger
represent more than half of the rear seat occupant population.\103\
---------------------------------------------------------------------------

\103\ See https://www.nhtsa.gov/crashworthiness/child-safety-
crashworthiness-
research#:~:text=Since%20children%2012%2Dyears%2Dold,booster%20seats%
20and%20seat%20belts (last accessed May 16, 2024).
---------------------------------------------------------------------------

Accordingly, specifying the 5th percentile female could result in
unbelted child occupants in the rear not benefiting from the seat belt
warning. For instance, if a negative-only system with occupant
detection did not detect an unbelted child smaller than the 5th
percentile female seated in a rear seat, the visual warning would not
indicate an unbelted occupant at an occupied seat (e.g., for systems
with a pictogram that indicates which seat are not in use, the
pictogram would likely display something like a ``grayed-out'' seat to
indicate that the system was registering a seat as unoccupied). In this
scenario, the driver may not realize that the system was not detecting
the child occupant and may think the child is buckled when they are
not. This concern is not hypothetical. The owner's manual for the MY
2024 Subaru Forester states that ``[t]he driver must check that all the
passengers have fastened their seatbelts properly since the seatbelt
warning system may not detect passengers under the following
circumstances.--When cushions or child restraint systems, etc., are
used--When a child or small adult is sitting in the seat.'' The fact
that the system does not work for some classes of occupants could also
lead the driver to be less likely to respond to accurate warnings.
These shortcomings could also affect consumer acceptance of the system.
Second, the concern about downgrading to a positive-only system is
alleviated because we have modified the proposal so that the final rule
does not dictate specific compliance options for the information
conveyed by the visual warning; the finalized requirements for the
visual warning allow all of the systems that would have been allowed
under the proposed rule, as well as additional systems that would not
have been allowed under the proposal.
Third, a very small percentage of vehicles currently sold in the
U.S. is equipped with rear-seat occupant detection. Based on the 2022
NCAP data, approximately seven percent of light vehicles have SBWS with
occupant detection for the rear seats. Relatedly, rear systems with
occupant detection are a relatively new feature in the U.S. vehicle
market. So even if some manufacturers were to stop offering occupant
detection, it would affect a relatively new feature on a small fraction
of vehicles offered for sale in the U.S. and would not be a meaningful
reduction in the choices presently offered to consumers.
Fourth, this trade-off may or may not materialize. The trade-off
would not occur if manufacturers develop and deploy rear-seat occupant
detection systems capable of detecting a 6-year-old within the allotted
lead time (two years).
Fifth, the possibility that some manufacturers may choose to forgo
occupant detection because the final rule specifies the 6-year-old does
not lead us to conclude that it would be preferable to specify the 5th
percentile female. We considered the relative benefits and costs of
specifying each of these systems.
The target population addressed by this rule will necessarily be
larger if we specify the 6-year-old--and, importantly, this addition to
the target population consists of children. Due to a lack of data, the
FRIA was unable to establish how much more effective a rear seat belt
reminder system with occupant detection would be relative to a seat
belt reminder system without occupant detection. However, it is
important to note that the baseline seat belt use rate for rear seat
occupants ages 6 to 10 years is already very high. As it is unlikely
that the seat belt use rate would reach 100 percent, this leaves very
little room for improvement. Accordingly, the children who will benefit
from the rule if we specify the 6-year-old is effectively children from
about ages 11-18. This is still a larger

[[Page 413]]

target population than if we specified the 5th percentile female.
Targeting this population points towards greater benefits.
On the other hand, if NHTSA specifies the 6-year-old, at least some
manufacturers may offer fewer rear seat belt reminder systems with
occupant detection. However, we are unable to estimate the overall
impact of this potential reduction because of several unknowns: how
many fewer systems with occupant detection will be offered; the
difference in effectiveness between systems with occupant detection and
systems without occupant detection; \104\ and the seat belt use rates,
injuries, or fatalities for children ages 11-18.\105\ We also believe
that any short-term decrease in net benefits (if that should in fact
materialize) is outweighed by what we anticipate to be the greater
benefits in the medium-to-long term for children. Moreover, specifying
the 6-year-old would result in seat belt reminder systems that are able
to reliably inform the driver of unbelted children in the rear seat.
While our regulatory analysis is not able to quantify these benefits to
an especially vulnerable occupant population, we recognize the
importance of these unquantified benefits. NHTSA therefore concludes
that specifying the 6-year-old appropriately balances benefits and
costs compared to specifying the 5th percentile female.
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\104\ The NPRM explained that while the main advantage is more
informative warnings and that it can reduce false warnings for
unoccupied seats, it can also (as pointed out by some commenters)
result in false warnings.
\105\ Because of data limitations, NHTSA was unable to break out
this information for this age group specifically. NHTSA was only
able to segment the analysis into occupants ages 6-10 and occupants
11 and older.
---------------------------------------------------------------------------

v. Duration
NHTSA proposed that the start-of-trip warning last for at least 60
seconds. We believed that 60 seconds would be sufficient to capture the
driver's attention and appropriately balanced effectiveness and
acceptance.
60 seconds is a shorter warning than we proposed for the front
outboard seats. There were a couple of reasons for our tentative
decision that a shorter warning is warranted for the rear seats. First,
we did not propose to require occupant detection for the rear seat belt
warning system; the positive-only compliance option would require that
the driver be informed of which rear seat belts are fastened. This type
of ``warning'' functions more to provide information to the driver,
rather than a true warning (because it will be providing information to
the driver even if all rear occupants have fastened their seat belts),
so we tentatively believed that it is not necessary to require that it
be particularly long-lasting. Second, and related, even for the
compliance options that would entail occupant detection, the
complexities of occupant detection in the rear seats and the
possibilities for false positives provide another reason for not
requiring an extremely long-lasting warning. Manufacturers would be
free to provide a longer warning.
This duration was consistent with ECE R16, Euro NCAP, and the IIHS
protocol, each of which requires a visual warning at the start of the
trip for the rear seat belts lasting at least 60 seconds. It is also
consistent with many of the rear seat belt warning systems currently
deployed in the United States. In the NPRM we noted that, of the
fifteen manufacturers that provide vehicle models with a rear seat belt
warning system in the United States, eight appeared to provide systems
with initial visual warnings that are active for at least 60 seconds.
An additional three manufacturers appeared to provide visual warnings
until the seat belt is fastened.
Comments
Auto Innovators, Freedman, Honda, HATCI, and Consumer Reports
supported a 60-second minimum requirement. Auto Innovators and HATCI
commented that this requirement would align with ECE R16.
SRN requested a longer-duration warning requirement. It argued that
the proposed warning would be only moderately effective (especially for
occupants of rideshare vehicles) because it could be easily ignored.
SRN also commented that caregivers, who may have children in car seats
and boosters, may need more time to interpret the warning. SRN also
suggested that a seat belt status indicator could be valuable as a
constant readout on the dashboard, as warning lights are sometimes
dismissed or ignored.
Agency Response
The final rule adopts the proposed 60-second minimum duration. We
believe this requirement appropriately balances effectiveness and
acceptance. A 2015 survey of drivers of vehicles with RSBWSs found that
28 percent of GM drivers noticed an increase in rear seat belt usage,
and 23 percent of Volvo drivers reported an increase in rear seat belt
usage.\106\ The GM system used a 30-second visual warning at start-up
and the Volvo system provided a short message at start-up, suggesting
that a 60-second warning would be at least as effective. The 60-second
minimum duration also harmonizes with ECE R16, Euro NCAP, and the IIHS
protocol.
---------------------------------------------------------------------------

\106\ Paul Schroeder & Melanie Wilbur, Survey of Principal
Drivers of Vehicles with a Rear Seat Belt Reminder System.
Washington, DC: National Highway Traffic Safety Administration
(2015).
---------------------------------------------------------------------------

A longer warning then 60 seconds could be annoying (in particular
for systems without occupant detection that display unfastened belts).
We also believe that 60 seconds is long enough to interpret the
warning. This is what some current systems use, and we have no
information to suggest that consumers have had difficulty interpreting
the warning. This is a minimum performance requirement so manufacturers
may voluntarily provide warnings lasting longer than 60 seconds. On the
other hand, we are aware of vehicles that provide shorter warnings, so
having a 60-second requirement will ensure a minimum level of
performance.
vi. Other Aspects
NHTSA also received comments on other aspects of the proposed rear
seat belt warning requirements.
Comments
Tesla requested that NHTSA clarify whether the ``rear rows''
reference includes all designated rear seating positions. Tesla also
commented asking if the agency had a plan to also address integrated
child seats that have seat belt reminder technology. Auto Innovators
commented that the proposed S7.5(c)(1)(ii), requiring a visual and
audible change of status warning, and S7.5(c)(2)(ii), prohibiting a
visual warning that a seat belt is not in use for an unoccupied seat,
are inconsistent and require clarification.
Agency Response
The final rule retains the reference to ``all rear designated
seating positions.'' The proposed regulatory text did not refer to
``rows''; it simply referred to ``rear designated seating positions.''
Accordingly, it applies to all rear designated seating positions in
applicable vehicles.
It is not necessary that the rule specifically address integrated
child seats. Integrated child seats are CRSs or booster seats that are
built into the vehicle seat. A child seated in an integrated child seat
is secured with either a seat belt or a harness. If the child is
secured with a seat belt, then the seat belt warning should monitor
belt use as with any seat belt. If the child is secured with a harness,
the seat belt reminder would not be required for the harness, because
children in an integrated seat with a harness are not part of the
target population for this rule

[[Page 414]]

just as children in rear- and forward-facing CRSs are not part of the
target population. In addition, we were unable to identify any new
vehicles with integrated child seats that use a harness. Integrated
booster seats would not pose an issue for the seat belt warning system,
and we are aware of only one vehicle manufacturer that offers
integrated booster seats on some vehicles as an option.\107\ Regarding
Auto Innovators comment, the final rule does not include the proposed
requirement that the warning is not permitted to indicate a seat belt
is not in use for an unoccupied seat because we do not believe this is
necessary.
---------------------------------------------------------------------------

\107\ See <a href="https://www.volvocars.com/lb/support/car/xc90/article/3212aabb4f810a77c0a8015146e81cc9">https://www.volvocars.com/lb/support/car/xc90/article/3212aabb4f810a77c0a8015146e81cc9</a> (last accessed May 16, 2024).
---------------------------------------------------------------------------

b. Audio-Visual Change-of-Status Warning
NHTSA proposed requiring an audio-visual warning when a rear seat
belt is unbuckled during a trip. We proposed that an audio-visual
warning must activate when the ignition switch is in the ``on'' or
``start'' position, the vehicle is in forward or reverse drive mode,
and the status of the seat belt changes from in use to not in use,
unless any rear door is open, in which case a change-of-status warning
would not be required. The exception for an open rear door was intended
to allow for passengers to exit the vehicle when the driver does not
shift into park without activating the change-of-status warning.
The audio-visual warning would have to last for at least 30 seconds
or until the seat belt that triggered the warning is in use. We
proposed that the audible signal may be ``intermittent'' (i.e., not
continuous), which mirrors the longstanding requirements for the
driver's seat belt warning. If intermittent, we proposed that inactive
periods longer than three seconds would not be counted toward the total
minimum duration of the audible warning. Because the required minimum
duration was relatively short, we did not propose additional audible
signal characteristics, such as a duty cycle. (In contrast, we proposed
additional signal characteristics for the front seat belt change-of-
status warning because of the required longer duration for that
warning. The final rule decisions on these aspects of the front seat
warning are discussed in Section VI.B.3).
ECE R16 similarly specifies an audio-visual change-of-status
warning for rear seats. Specifically, if a fastened belt becomes
unfastened when the vehicle is in ``normal operation'' (defined as
forward motion at a speed greater than 10 km/h (6.2 mph)),\108\ ECE R16
specifies an audio-visual warning (second level) when certain distance,
time, and/or speed threshold(s) (at the choice of the manufacturer) are
exceeded.\109\ The additional thresholds are distance traveled (not to
exceed 500 meters), vehicle speed (not to exceed 25 km/h (15.5 mph),
and/or travel time (not to exceed 60 sec). This warning must last for
at least 30 seconds unless the unfastened belt becomes fastened, the
seat associated with the unfastened belt is no longer occupied, or the
vehicle is no longer in normal operation.\110\ This warning may not be
canceled by the driver.
---------------------------------------------------------------------------

\108\ Section 2.47.
\109\ Section 8.4.3.3 (front seat belts) and section 8.4.4.5
(rear seat belts).
\110\ These summaries simplify the requirements somewhat. They
will be discussed in greater detail later in the preamble where
relevant.
---------------------------------------------------------------------------

Euro NCAP also requires (to earn points) an audio-visual change-of-
status warning at vehicle speeds of 25 km/h (15.5 mph) and above.\111\
If the change of status occurs below 25 km/h (15.5 mph) and no doors
are opened, the signal may be delayed until the vehicle has been in
forward motion for 500 meters or has reached a forward speed of 25 km/h
(15.5 mph).\112\ A warning is not required if the system has occupant
detection as long as all doors remain closed and the number of buckled
positions remains the same, in order to minimize the number of false
positives (e.g., children remaining in the vehicle but swapping seats
in the rear while at a traffic light).\113\ The warning duration
differs for the visual and audible warnings. With respect to the visual
warning, if the system does not have occupant detection, the warning
must last until the seat belt is fastened or 60 seconds have
elapsed.\114\ If the system does have occupant detection, the signal
must remain on until the belt is fastened. The audible warning must
last until the belt is fastened,\115\ 30 seconds have elapsed,\116\ or
the vehicle speed falls below 10 km/h (6.2 mph).\117\
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\111\ Section 3.4.1.5.
\112\ Section 3.4.1.5.
\113\ Section 3.4.1.5.
\114\ Section 3.4.3.1.1.
\115\ Section 3.4.1.6.
\116\ Section 3.4.3.2.
\117\ Section 3.4.1.6. The audio signal must resume when the
speed goes above 25 km/h (15.5 mph) and no doors have been opened
and the seat belt(s) remain unbuckled. In addition, the audible
signal may instead meet the requirements for the front seating
positions, if the vehicle is equipped with occupant detection.
---------------------------------------------------------------------------

ECE R16 \118\ and Euro NCAP \119\ do not count periods in which the
warning stops for longer than three seconds as part of the overall
duration.
---------------------------------------------------------------------------

\118\ Section 8.4.2.4.1.
\119\ Section 3.4.3.2.3.
---------------------------------------------------------------------------

The IIHS protocol also requires an audio-visual change-of-status
warning lasting at least 30 seconds when the vehicle is in motion. The
exact trigger depends on vehicle speed. When vehicle speed is between
10 and 40 km/h (6.2 and 24.9 mph), the audio-visual warning must start
within 30 seconds of continuous forward motion, and when the speed
exceeds 40 km/h (24.9 mph), the audio-visual warning must begin within
two seconds if the signal has not already begun. The warning can
deactivate when the seat belt that triggered the warning is fastened;
the vehicle is no longer in forward motion above 10 km/h (6.2 mph); or
the seat or seats that triggered the warning are no longer occupied.
Similar to Euro NCAP, the thresholds to trigger the primary audible
signal and visual signal may be reset if any doors have been opened
when the vehicle is not in motion.
The proposal differed from ECE R16, Euro NCAP, and the IIHS
protocol in some respects. The proposed 30-second duration was shorter
than the 60-second duration for the visual signal specified in Euro
NCAP, but consistent with the 30-second duration for the audible
signal. We also did not propose any speed, distance, or time triggers.
And we did not propose the Euro NCAP allowance for not requiring a
change-of-status warning when all doors remain closed and the number of
buckled positions remains the same because it would require a delay in
the activation of the change-of-status warning; also, these types of
events are likely uncommon and require very little time to complete, so
exposure to the warning would be very limited.
Comments
Consumer Reports agreed with the agency's decision to require the
change-of-status warning to include both audible and visual components.
It also supported departing from ECE R16 and Euro NCAP and requiring a
warning whether or not a vehicle is in motion because a stopped vehicle
presents the best opportunity for the driver to ensure that the
occupants are belted.
On the other hand, Honda, Nissan, NADA, Tesla, Ford, Auto
Innovators, and HATCI commented that reminder trigger conditions should
harmonize with ECE R16 and/or Euro NCAP and be based on vehicle motion.
Auto Innovators and Honda commented that the proposed requirements for
providing an audible alert may result in widespread consumer acceptance
issues. For example, Auto Innovators argued that establishing a trigger

[[Page 415]]

threshold based solely on the ignition being on, absent vehicle motion,
will result in scenarios where an unbelted condition that may otherwise
be viewed as reasonably acceptable would result in an audible alarm,
including those where the vehicle is either stopped (and in drive) or
slowing in anticipation of an upcoming stop (e.g., in a rideshare
scenario or school drop-off). Auto Innovators recommended that NHTSA
harmonize with ECE R16, which requires the audio-visual warning to be
provided only when there is a change in seat belt status when the
vehicle is traveling above 25 km/h (15.5 mph) or moving below 25 km/h
(15.5 mph) for a period of 60 seconds.
Auto Innovators further commented that the agency did not
articulate why it has proposed that an audible alert occur when the
vehicle is in reverse. Auto Innovators explained that such maneuvers
are typically low-speed events, and that the agency has not provided
clear justification for why an audible alert is needed in these
scenarios.
Honda commented that if NHTSA does not adopt a speed threshold, it
could consider an alternative approach that would allow a single chime
when the change of status occurs (assuming the vehicle is stationary)
and then resume the full alarm when the vehicle begins moving. Honda
commented this modification w

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