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Proposed Rule2023-19008

Anthropomorphic Test Devices; THOR 50th Percentile Adult Male Test Dummy; Incorporation by Reference

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Published

September 7, 2023

Issuing agencies

Transportation DepartmentNational Highway Traffic Safety Administration

Abstract

This document proposes to amend NHTSA's regulations to include an advanced crash test dummy, the Test Device for Human Occupant Restraint (THOR) 50th percentile adult male (THOR-50M). The dummy represents an adult male of roughly average height and weight and is designed for use in frontal crash tests. NHTSA plans to issue a separate NPRM to amend Federal Motor Vehicle Safety Standard (FMVSS) No. 208, "Occupant crash protection," to specify the THOR-50M as an alternative (at the vehicle manufacturer's option) to the 50th percentile adult male dummy currently specified in FMVSS No. 208 for use in frontal crash compliance tests.

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[Federal Register Volume 88, Number 172 (Thursday, September 7, 2023)]
[Proposed Rules]
[Pages 61896-61949]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-19008]

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Vol. 88

Thursday,

No. 172

September 7, 2023

Part VI

Department of Transportation

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National Highway Traffic Safety Administration

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49 CFR Part 572

Anthropomorphic Test Devices; THOR 50th Percentile Adult Male Test
Dummy; Incorporation by Reference; Proposed Rule

Federal Register / Vol. 88, No. 172 / Thursday, September 7, 2023 /
Proposed Rules

[[Page 61896]]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 572

[Docket No. NHTSA-2023-0031]
RIN 2127-AM20

Anthropomorphic Test Devices; THOR 50th Percentile Adult Male
Test Dummy; Incorporation by Reference

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to amend NHTSA's regulations to include
an advanced crash test dummy, the Test Device for Human Occupant
Restraint (THOR) 50th percentile adult male (THOR-50M). The dummy
represents an adult male of roughly average height and weight and is
designed for use in frontal crash tests. NHTSA plans to issue a
separate NPRM to amend Federal Motor Vehicle Safety Standard (FMVSS)
No. 208, ``Occupant crash protection,'' to specify the THOR-50M as an
alternative (at the vehicle manufacturer's option) to the 50th
percentile adult male dummy currently specified in FMVSS No. 208 for
use in frontal crash compliance tests.

DATES: You should submit your comments early enough to be received not
later than November 6, 2023.
Proposed Effective Date: Since this rulemaking action would not
impose requirements on anyone, we are proposing that the final rule
would be effective on publication in the Federal Register.

ADDRESSES: You may submit comments electronically to the docket
identified in the heading of this document by visiting the Federal
eRulemaking Portal at <a href="http://www.regulations.gov">http://www.regulations.gov</a>. Follow the online
instructions for submitting comments.
Alternatively, you can file comments using the following methods:
<bullet> Mail: Docket Management Facility: U.S. Department of
Transportation, 1200 New Jersey Avenue SE, West Building Ground Floor,
Room W12-140, Washington, DC 20590-0001.
<bullet> Hand Delivery or Courier: West Building Ground Floor, Room
W12-140, 1200 New Jersey Avenue SE, between 9 a.m. and 5 p.m. ET,
Monday through Friday, except Federal holidays. To be sure someone is
there to help you, please call (202) 366-9826 before coming.
<bullet> Fax: (202) 493-2251.
Instructions: All submissions must include the agency name and
docket number or Regulatory Information Number (RIN) for this
rulemaking. For detailed instructions on submitting comments and
additional information on the rulemaking process, see the Public
Participation heading of the Supplementary Information section of this
document. Note that all comments received will be posted without change
to <a href="http://www.regulations.gov">http://www.regulations.gov</a>, including any personal information
provided. Please see the Privacy Act heading below.
Docket: For access to the docket to read background documents or
comments received, go to <a href="http://www.regulations.gov">http://www.regulations.gov</a>. You may also
access the docket at 1200 New Jersey Avenue SE, West Building, Room
W12-140, Washington, DC 20590, between 9 a.m. and 5 p.m., Monday
through Friday, except Federal Holidays. Telephone: 202-366-9826.
Confidential Business Information: If you claim that any of the
information in your comment (including any additional documents or
attachments) constitutes confidential business information within the
meaning of 5 U.S.C. 552(b)(4) or is protected from disclosure pursuant
to 18 U.S.C. 1905, please see the detailed instructions given under the
Public Participation heading of the Supplementary Information section
of this document.
Privacy Act: Please see the Privacy Act heading under the
Regulatory Analyses section of this document.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact
Mr. Garry Brock, Office of Crashworthiness Standards, Telephone: (202)
366-1740; Email: <a href="/cdn-cgi/l/email-protection#9cdbfdeeeee5b2deeef3fff7dcf8f3e8b2fbf3ea">[email&#160;protected]</a>; Facsimile: (202) 493-2739. For
legal issues, you may contact Mr. John Piazza, Office of Chief Counsel,
Telephone: (202) 366-2992; Email: <a href="/cdn-cgi/l/email-protection#165c797e7838467f776c6c775672796238717960">[email&#160;protected]</a>; 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. Design, Construction, and Instrumentation
A. Anthropometry
B. Technical Data Package
C. Head and Face
D. Neck
E. Chest
1. Design
2. Instrumentation
F. Shoulder
1. Alternate Shoulder Specification
2. Shoulder Slip
G. Hands
H. Spine
I. Abdomen
J. Pelvis
K. Upper Leg
L. Knee
M. Lower Leg
N. Data Acquisition System
IV. Biofidelity
V. Qualification Tests
A. Head Impact
B. Face Impact
C. Neck
D. Upper Thorax
E. Lower Thorax
F. Abdomen
G. Upper Leg
H. Knee and Lower Leg
VI. Repeatability and Reproducibility
A. Qualification Tests
B. Sled Tests
1. Methodology
2. Thoracic Injury Criteria Development Sled Tests
3. Low-Speed Belted Sled Tests
4. Low-Speed Unbelted Sled Tests
VII. Overall Usability and Performance
A. Assembly and Qualification
B. Durability and Maintenance
1. Elevated Energy Qualification Test Series
2. Oblique OMDB Test Series
3. FMVSS No. 208 Unbelted Vehicle Crash Tests
C. Sensitivity to Restraint System Performance
VIII. Intellectual Property
IX. Consideration of Alternatives
X. Lead Time
XI. Incorporation by Reference
XII. Regulatory Analyses
XIII. Public Participation
Proposed Regulatory Text

I. Executive Summary

This document proposes to amend NHTSA's regulation on
anthropomorphic test devices--or, more colloquially, crash test
dummies--to include an advanced crash test dummy, the Test Device for
Human Occupant Restraint (THOR) 50th percentile adult male (THOR-50M).
The dummy represents an adult male of roughly average height and weight
and is designed for use in frontal crash tests.
Crash test dummies are complex instruments that simulate the
response of a human occupant in a crash. Each type of test dummy is
designed for use in specific types of crashes (for instance, frontal or
side) and is instrumented with sensors to measure the forces that would
have been experienced by a human occupant in a similar crash in the
real world. These measurements are then used to assess the potential
for injury.
Crash test dummies are used by NHTSA and by the broader vehicle
safety community in a variety of ways.

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NHTSA uses crash test dummies to test vehicles for compliance with
Federal Motor Vehicle Safety Standards (FMVSSs) and to determine
vehicle crashworthiness ratings for the New Car Assessment Program's
(NCAP) 5-Star Safety Ratings, as well as to conduct vehicle safety
research. Crash test dummies are also used by regulatory authorities in
other countries and regions, third-party vehicle rating programs, motor
vehicle and equipment manufacturers, and others to evaluate vehicle
safety and design safer vehicles and equipment.
The dummies NHTSA currently uses in FMVSS compliance testing and
NCAP are documented in 49 CFR part 572, Anthropomorphic Test Devices.
Part 572 sets out detailed design information, including engineering
drawings and procedures for assembly and inspection. These are intended
to describe the dummy with sufficient detail so that it is an objective
measuring tool that produces consistent responses. NHTSA has codified
numerous dummies that range in sex, size, age, and measurement
capability. This includes dummies representing midsize adult males,
small-stature adult females, infants, toddlers, and older children.\1\
These dummies are meant to provide a range of body types in order to
maximize data and test results that can assess injury and fatality
risks in a range of crash outcomes. The 50th percentile male dummy
currently defined in Part 572 for frontal impacts is the Hybrid III-
50M, which NHTSA uses to test for compliance with the frontal crash
test requirements in FMVSS No. 208, ``Occupant crash protection'' and
to rate vehicles for NCAP. NHTSA added the HIII-50M to Part 572 in
1986.
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\1\ This reflects a ``bookend'' approach to testing vehicles for
crashworthiness, in which a range of occupant types, bookended by an
average male and a small-stature female, is tested. NHTSA is
currently supporting research to assess the possible benefits of
developing new crash test dummies, such as a 50th percentile female
crash test dummy.
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NHTSA is continually researching and improving its test dummies and
has been researching advanced test dummies since the implementation of
the HIII-50M. An initial THOR-50M design was published in 2001. There
are currently two different THOR dummies, the THOR-50M, and one under
development that represents a small-statured adult female, the THOR 5th
percentile adult female (THOR-05F). Although this proposal is limited
to the THOR-50M, we anticipate publishing a rulemaking proposal in the
near future to add the THOR-05F to Part 572.
The THOR-50M improves on the HIII-50M in a number of ways. It
responds more like a human occupant in a crash and its advanced
instrumentation enables it to more accurately measure the forces acting
on the dummy. As a result, it is better able to predict the risk of
injury to a human occupant. This should help vehicle designers develop
and test improved occupant restraint systems (e.g., advanced seat belts
and air bags) as well as the types of novel vehicle seating
configurations likely to be used in highly automated vehicles.
NHTSA has tentatively concluded that the THOR-50M is sufficiently
biofidelic, exhibits repeatable and reproducible performance, and is
sufficiently durable. As such, we believe that it would be suitable for
use in regulatory compliance testing and is therefore suitable for
incorporation into Part 572. NHTSA and others have already taken
advantage of the THOR-50M's advanced capabilities. NHTSA, vehicle and
restraint manufacturers, and vehicle safety researchers have used the
THOR-50M to evaluate vehicle crashworthiness and develop occupant
protection countermeasures for frontal and oblique crashes. The
European New Car Assessment Programme (Euro NCAP) has officially
adopted the THOR-50M and is currently rating vehicles using the dummy.
Moreover, the Economic Commission for Europe is considering adopting
the THOR-50M for use in frontal crash testing under its vehicle safety
regulations.
NHTSA expects a variety of benefits from incorporating the THOR-50M
into Part 572. The definition of the THOR-50M in Part 572 will enable
its use in regulatory and consumer information programs, both within
NHTSA and externally. NHTSA believes that the THOR-50M's enhancements
will lead to more effective restraint system designs and more
informative comparisons of the safety of different vehicles. Because of
this--as well as the fact that manufacturers are already using the
dummy--we believe vehicle manufacturers would choose to certify
vehicles to FMVSS No. 208 using the THOR-50M if given the option. This
would enable manufacturers to streamline testing by using the same
dummy for research and development and to verify compliance. NHTSA
anticipates issuing a proposal in the near future to amend FMVSS No.
208 to specify the THOR-50M as an alternative (at the vehicle
manufacturer's option) to the HIII-50M test dummy for use in frontal
crash compliance tests. There would be other benefits as well. For
instance, NHTSA's test dummies are used in a range of applications
beyond FMVSS compliance testing--such as NCAP testing, standards and
regulations in other transportation modes, and research. Including the
dummy design in Part 572 will help provide a suitable, standardized,
and objective test tool for the safety community.

II. Background

This document proposes to amend 49 CFR part 572, Anthropomorphic
Test Devices, to include an advanced test dummy representing a 50th
percentile adult male, the Test Device for Human Occupant Restraint
(THOR-50M).\2\ The THOR-50M is a test dummy designed for use in frontal
crash tests. It has several advanced capabilities and advantages over
the Hybrid III 50th percentile male test dummy (HIII-50M) that is
currently specified in Part 572 and used in frontal crash testing under
FMVSS No. 208, ``Occupant crash protection,'' and the U.S. New Car
Assessment Program (NCAP).\3\ NHTSA plans to issue a proposal in the
near future to amend FMVSS No. 208 to specify the THOR-50M as an
alternative to the HIII-50M for use in frontal crash tests.\4\
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\2\ NHTSA has registered the term ``THOR'' as a trademark (U.S.
Registration No. 5,104,395).
\3\ The HIII-50M is also specified for use in FMVSS No. 202a,
Head Restraints, in an optional rear impact dynamic test.
\4\ FMVSS No. 208 THOR-50M Compliance Option (RIN 2127-AM21),
Spring 2023 Unified Agenda of Regulatory and Deregulatory Actions;
Department of Transportation, available at <a href="https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21">https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21</a>.
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This document proposes incorporating by reference in Part 572 a
parts list, design drawings, qualification procedures, and procedures
for assembly, disassembly, and inspection, to ensure that THOR-50M
dummies are uniform in design, construction, and response. This section
provides background on NHTSA's crash test dummies, the development of
the THOR-50M, and its use in other jurisdictions, among other topics.

Overview of Use of Vehicle Crash Test Dummies

Anthropomorphic Test Devices (ATDs)--or crash test dummies--are
complex instruments that serve as human surrogates in vehicle crash
tests (among other types of tests \5\). Test dummies simulate the
response of a human occupant in a crash and measure

[[Page 61898]]

the effects of the crash forces on the occupant. They are used to
estimate the severity of the injuries that would have been experienced
by a human occupant in a similar crash in the real world. Each type of
test dummy is designed for use in specific types of crashes (frontal,
side, etc.), and is instrumented with a wide array of sensors to
measure the forces that would be relevant in the type of crash for
which it is designed and to assess the potential for injury. The more
closely a dummy represents how an actual human would respond, the more
biofidelic the dummy is considered to be.
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\5\ NHTSA also uses ATDs in sled tests (which simulate a vehicle
crash by using a simplified test buck to represent a vehicle), and
out-of-position air bag tests. ATDs are also used outside the
vehicle safety context to measure human responses in a variety of
other areas, such as aviation and aeronautics.
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NHTSA and the vehicle safety community use crash test dummies in a
variety of ways. NHTSA uses crash test dummies for vehicle compliance
testing, safety ratings, and safety research. NHTSA's Federal Motor
Vehicle Safety Standards establish mandatory minimum safety performance
requirements for motor vehicles and motor vehicle equipment. Vehicles
and equipment manufactured for sale in the United States must be
certified to comply with all applicable FMVSSs. A number of the FMVSSs
specify crash tests, using specified dummies, that the vehicle must be
certified as passing.\6\ NHTSA's vehicle safety compliance program
selects vehicles (and equipment) for compliance testing every year;
this includes crash testing vehicles to ensure that they comply with
the performance requirements that are evaluated by means of crash
tests. NHTSA's NCAP also evaluates vehicle performance in crash tests
using dummies as part of its 5-Star Safety Ratings. Finally, NHTSA's
vehicle safety research program uses crash test dummies to evaluate new
vehicle safety countermeasures and develop new vehicle crash testing
protocols. Dummies are also used outside of NHTSA by regulatory
authorities in other countries and regions, for third-party ratings
(such as Insurance Institute for Highway Safety ratings), and by
industry and the vehicle safety community to measure performance and
design safer vehicles.
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\6\ The FMVSS specify the procedures NHTSA will use in
compliance testing, including what dummies it will use for testing.
Part 572 specifies the dummies. While manufacturers must exercise
reasonable care in certifying that their products meet applicable
standards, they are not required to follow the compliance test
procedures set forth in a standard or use the dummy specified in
Part 572. See, e.g., 38 FR 12934, 12935 (May 17, 1973)
(``Manufacturers should understand that they are not required to
test their products in any particular manner, as long as they
exercise due care that their products will meet the requirements
when tested by the NHTSA under the procedures specified in the
standard.'').
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The dummies NHTSA currently uses in FMVSS compliance testing and in
NCAP are documented in 49 CFR part 572, Anthropomorphic Test Devices.
Part 572 sets out detailed design information, including engineering
drawings and procedures for assembly and inspection. These are all
intended to describe the dummy with sufficient detail so that it
produces consistent responses when it is tested under similar
conditions in repeated tests at the same laboratory (repeatability) or
between multiple dummies manufactured to the same specification used at
different test laboratories (reproducibility).

FMVSS No. 208 Frontal Crash Tests Using a 50th Percentile Male Dummy

FMVSS No. 208, ``Occupant crash protection,'' specifies a variety
of different requirements using crash test dummies. This includes
frontal crash tests in which the vehicle is moving and tests that are
performed with a stationary vehicle and are intended to help ensure
that air bags do not harm small-stature occupants and children. The
test dummies used in FMVSS No. 208 were designed to evaluate vehicle
performance in frontal crashes and are fitted with a variety of
instruments to measure the forces typically experienced by an occupant
in a frontal crash.\7\ The 50th percentile male dummy that is currently
specified for use in FMVSS No. 208 is the Hybrid III-50M.\8\ The HIII-
50M has been specified in FMVSS No. 208 since 1986,\9\ and replaced an
even earlier dummy, the Hybrid II. FMVSS No. 208 also specifies tests
using dummies representing a 5th percentile female, a 6-year-old, a 3-
year-old, and an infant.\10\
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\7\ Other FMVSS specify different types of crash or sled tests
that use different dummies. For example, FMVSS No. 214, Side Impact
Protection, specifies two crash tests (simulating a side impact with
a vehicle and a pole impact). This test uses two different side
impact dummies.
\8\ Part 572, Subpart E.
\9\ 51 FR 26688 (July 25, 1986) (final rule adding HIII-50M).
The Hybrid III-50M was developed by General Motors and added to Part
572 and for use in FMVSS No. 208 in response to a petition for
rulemaking from GM.
\10\ This reflects a ``bookend'' approach to testing vehicles
for crashworthiness, in which a range of occupant types, bookended
by an average male and a small-stature female, is tested. NHTSA is
currently supporting research to assess the possible benefits of
developing new crash test dummies, such as a 50th percentile female
crash test dummy.
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FMVSS No. 208 specifies two tests (both of which are crash tests)
using the HIII-50M: a crash test in which the dummy is belted and the
test vehicle, traveling up to 35 mph, impacts a rigid barrier at a
ninety-degree angle or perpendicular; \11\ and a crash test in which
the dummy is unbelted and the test vehicle, traveling 20-25 mph,
impacts a rigid barrier at an angle ranging from <plus-minus> 30
degrees oblique from perpendicular.\12\ NCAP also evaluates vehicle
performance in a frontal crash test at 35 mph using a belted HIII-50M
dummy.
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\11\ S5.1.1(b)(2), S14.5.1(b).
\12\ S5.1.2(b), S14.5.2.
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FMVSS No. 208 regulates vehicle performance in these crash tests by
specifying injury criteria and associated injury assessment reference
values (IARVs). Injury criteria and their respective risk functions
relate instrumentation measurements to a predicted risk of human
injury. Each IARV is a maximum value or threshold for a specific injury
criterion that may not be exceeded when the vehicle is tested with the
specified dummy under the specified test conditions and procedures. For
example, FMVSS No. 208 specifies a head injury criterion,
HIC<INF>15</INF>, with an IARV of 700. Thus, if NHTSA runs a compliance
frontal crash test and the calculated HIC<INF>15</INF> value exceeds
700, this would be considered an apparent noncompliance. FMVSS No. 208
specifies the following injury criteria for the HIII-50M: a head injury
criterion (HIC<INF>15</INF>); \13\ a thoracic acceleration criterion;
\14\ a chest deflection criterion; \15\ a criterion based on the
maximum force transmitted axially through the upper leg (femur); \16\
and three neck injury criteria.\17\
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\13\ S6.2(b).
\14\ S6.3.
\15\ S6.4.
\16\ S6.5.
\17\ S6.6.
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Development of the THOR ATDs

NHTSA has continually conducted research into advancements in crash
safety, including the development of advanced dummies.\18\ The goal of
this research has been to create ATDs that represent the responses of
human occupants in modern vehicle environments with advanced restraint
systems. This research has led to the development of the two Test
Device for Human Occupant Restraint (THOR) ATDs, designed primarily for
use in frontal and frontal oblique motor vehicle crash environments.
There are currently two main implementations of the THOR design, both
representing seated motor vehicle occupants: one representing a 50th
percentile male and

[[Page 61899]]

one representing a 5th percentile female.
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\18\ Haffner, M., Rangarajan, N., Artis, M., Beach, D.,
Eppinger, R., Shams, T., ``Foundations and Elements of the NHTSA
THOR Alpha ATD Design,'' The 17th International Technical Conference
for the Enhanced Safety of Vehicles, Paper No. 458, 2001.
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Development of THOR-50M

The initial design version of the THOR-50M, introduced in 2001, was
the THOR Alpha.\19\ The THOR Alpha, which integrated some components
from the earlier prototype demonstrator known as the Trauma Assessment
Device, introduced some of the features that exist in the current
version of THOR-50M, including the multi-direction neck, human-like
ribcage geometry and impact response, multi-point thorax and abdomen
deflection measurement system, and instrumented lower extremities.
NHTSA refined the THOR Alpha design and reintroduced it in 2005 as the
THOR-NT,\20\ which included updates to anthropometry, durability,
usability, biofidelity, and fit and finish. In 2011, NHTSA, in
coordination with the SAE International (SAE) THOR Evaluation Task
Group, introduced a modification package (Mod Kit) intended to enhance
the biofidelity, repeatability, durability, and usability of the THOR-
NT.\21\ After the introduction of the THOR Mod Kit, an upgrade to the
Chalmers shoulder assembly that was developed through the European
Union's THORAX project was integrated into the THOR-50M design.\22\ The
THOR-50M drawing package was then converted from the traditional
measurement system to the metric system through soft conversion (where
any non-metric measurements are mathematically converted to metric
equivalents without changes to the physical dimensions). All fasteners
were also replaced with the nearest metric equivalents. NHTSA made this
integrated drawing package (with incremental improvements and
corrections) publicly available online in 2015,\23\ 2016,\24\ 2020,\25\
and 2023.\26\ The version published in 2023 is referred to as the 2023
drawing package, which consists of two-dimensional drawings and a Parts
list; this, together with the Procedures for Assembly, Disassembly, and
Inspection (PADI), and qualification procedures, is referred to as the
2023 technical data package. (The version published in 2020 is referred
to as the ``2018 drawing package'' or the ``2018 technical data
package.'') The version of THOR that is being proposed is the version
defined in the 2023 technical data package. In 2019, NHTSA began
publishing THOR-50M documentation in a new docket titled, ``NHTSA
Crashworthiness Research--THOR-50M Documentation.'' \27\ In addition to
the documents that make up the 2018 and 2023 technical data packages,
the docket folder includes the following: durability report; seating
procedure; injury criteria; biofidelity report; Oblique Moving
Deformable Barrier (OMDB) Repeatability and Reproducibility (R&R); and
Qualification test R&R. This documentation is discussed further in
Section III.B and in the relevant sections of this preamble.\28\ NHTSA
has tentatively concluded that the THOR-50M is sufficiently biofidelic,
exhibits repeatable and reproducible performance, and is sufficiently
durable. As such, we believe that it would be suitable for use in
regulatory compliance testing and is therefore suitable for
incorporation into Part 572. A more detailed discussion of the
technical data package is provided in Section III.B.
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\19\ Id.
\20\ Shams, T., Rangarajan, N., McDonald, J., Wang, Y., Platten,
G., Spade, C., Pope, P., Haffner, M., ``Development of THOR NT:
Enhancement of THOR Alpha--the NHTSA Advanced Frontal Dummy,'' The
19th International Technical Conference for the Enhanced Safety of
Vehicles, Paper No. 05-0455, 2005.
\21\ Ridella, S., Parent, D., ``Modifications to Improve the
Durability, Usability, and Biofidelity of the THOR-NT Dummy,'' The
22nd International Technical Conference for the Enhanced Safety of
Vehicles, Paper No. 11-0312, 2011.
\22\ Lemmen, P., Been, B., Carroll, J., Hynd, D., Davidsson, J.,
Song, E., Lecuyer, E., ``Development of an advanced frontal dummy
thorax demonstrator,'' Proceedings of the 2012 IRCOBI Conference,
2012.
\23\ National Highway Traffic Safety Administration (2015).
Parts List and Drawings, THOR-M Advanced Frontal Crash Test Dummy,
September 2015. <a href="http://Regulations.gov">Regulations.gov</a> Docket ID NHTSA-2015-0119-0005,
available at: <a href="https://www.regulations.gov/document/NHTSA-2015-0119-0005">https://www.regulations.gov/document/NHTSA-2015-0119-0005</a> (NCAP docket).
\24\ National Highway Traffic Safety Administration (2016).
Parts List and Drawings, THOR-50M Advanced Frontal Crash Test Dummy,
August 2016, available at: <a href="https://www.nhtsa.gov/es/document/thor-50m-drawing-package-august-2016.pdf">https://www.nhtsa.gov/es/document/thor-50m-drawing-package-august-2016.pdf</a>.
\25\ National Highway Traffic Safety Administration. Parts List
and Drawings, THOR-50M Advanced Frontal Crash Test Dummy, August
2018. <a href="http://Regulations.gov">Regulations.gov</a> Docket ID NHTSA-2019-0106-0002, available at:
<a href="https://www.regulations.gov/document/NHTSA-2019-0106-0002">https://www.regulations.gov/document/NHTSA-2019-0106-0002</a>.
\26\ National Highway Traffic Safety Administration. THOR 50th
Percentile Male with Alternate Shoulders Frontal Crash Test Dummy
Drawings, External Dimensions, and Mass Properties, THOR-50M
Advanced Frontal Crash Test Dummy, August 2018. <a href="http://Regulations.gov">Regulations.gov</a>
Docket ID NHTSA-2019-0106-0013, available at: <a href="https://www.regulations.gov/document/NHTSA-2019-0106-0013">https://www.regulations.gov/document/NHTSA-2019-0106-0013</a>.
\27\ Docket NHTSA-2019-0106.
\28\ These documents are located in the research docket, Docket
No. NHTSA-2019-0106. NHTSA is not placing copies of these documents
in the docket for this rulemaking action in order to avoid potential
confusion from having identical documents docketed at different
times in different dockets. Nevertheless, NHTSA intends these to be
included as part of the rulemaking record for this rulemaking
action. A memorandum explaining this is also being placed in the
docket for this rulemaking.
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Development of THOR-05F

NHTSA understands that the risk of injury in a crash can depend on
the occupant's physical characteristics (e.g., height, weight, bone
density) and how they interact with the restraint system and vehicle
environment. To that end, NHTSA has developed comprehensive research
plans to address differences in crashworthiness safety testing and
outcomes, including differences in injury risk. Human body modeling
research efforts are underway to consider female and male occupants and
vulnerable road users of various ages, shapes, and sizes. This includes
continuing and accelerating research efforts to address differences in
motor vehicle safety based on physical characteristics, including sex,
and making data-driven decisions supported by the research outcomes. A
series of efforts is specifically focused on female occupant crash
safety, spanning field data analysis, tool development, demonstration,
and application.\29\
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\29\ See National Highway Traffic Safety Administration (2022).
NHTSA Female Crash Safety Research Plan, November 2022.
<a href="http://Regulations.gov">Regulations.gov</a> Docket ID NHTSA-2022-0091-0002, available at:
<a href="https://www.regulations.gov/document/NHTSA-2022-0091-0002">https://www.regulations.gov/document/NHTSA-2022-0091-0002</a>.
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As part of these efforts, NHTSA has been developing the THOR 5th
percentile adult female frontal crash test dummy (THOR-05F). The THOR-
05F represents a small adult female and has a seated height of 81.3 cm
(32.0 in), approximate standing height of 151 cm (59.4 in), and weight
of 49 kg (108.0 lbs). The THOR-05F has improved measurement
capabilities over the Hybrid III-5F, which is specified in FMVSS No.
208 and documented in Part 572. The THOR-05F's instrumentation is
similar to that of the THOR-50M. Improved designs resulting from the
development of the THOR-50M related to the head, neck, thorax, and
lower extremities have also been incorporated into the design of the
THOR-05F. Currently, NHTSA is evaluating the THOR-05F's biofidelity and
durability, developing design updates, injury criteria, and
documentation, and assessing its utility in full-scale crash testing.
NHTSA anticipates completing the research and testing necessary to
support a rulemaking for the THOR-05F

[[Page 61900]]

in 2023.\30\ Possible test modes in which THOR-05F may be used include
FMVSS No. 208 testing and NCAP frontal crash tests. NHTSA has placed
documentation and research for the THOR-05F in an online docket and
will continue adding additional research and information to this docket
as it becomes available.\31\
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\30\ Part 572 THOR 5th Female Crash Test Dummy (RIN 2127-AM56),
Spring 2023 Unified Agenda of Regulatory and Deregulatory Actions;
Department of Transportation, available at <a href="https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM56">https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM56</a>. This
rulemaking would amend 49 CFR part 572 by adding design and
performance specifications for a new test dummy known as the THOR-
05F.
\31\ See Docket No. NHTSA-2019-0107, available at
regulations.gov.
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Innovative Features of the THOR-50M

Frontal crashes are the leading cause of injuries and fatalities in
occupants of motor vehicle crashes on U.S. public roadways. The vehicle
front is the initial point of impact in a majority of crashes in the
U.S. In 2021, 15,570 occupants of passenger cars or light trucks died,
and 1,144,169 were injured, in frontal crashes.\32\ This suggests that
even though occupant protection systems have improved over the years
and saved many lives,\33\ improvements to occupant protection in
frontal crashes still need to be made.
---------------------------------------------------------------------------

\32\ Data Sources: Fatality Analysis Reporting System (FARS):
2017-2020 Final File and 2021 Annual Report File (ARF); Report
Generated: Wednesday, June 28, 2023 (12:48:52 p.m.); VERSION 5.6,
RELEASED MAY 19, 2023
\33\ 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).
---------------------------------------------------------------------------

The THOR-50M is designed to better evaluate the effectiveness of
modern vehicle restraint systems and address the types of injuries that
continue to occur. These improvements include the following:
Improved biofidelity. Biofidelity is a measure of how well a dummy
replicates the response of a human. The THOR-50M was designed with
advanced features that enable it to have improved biofidelity compared
to the HIII-50M. The dummy's head includes a deformable facial insert
that emulates human response to impact. The components in the neck
representing bone and ligament structure are separate from those
representing muscular structure, improving both kinematic response and
injury prediction. The thorax simulates the shape and impact response
of the human rib cage. The spine incorporates flexible joints in the
thoracic and lumbar spine, allowing dynamic spine flexion as well as
static adjustment in the neck and lumbar spine to accommodate seating
in various postures. The upper leg has a compressive element in the
femur and the lower leg has a compressive element in the tibia and an
Achilles tendon load path to achieve human-like impact response. The
biofidelity of the THOR-50M has been assessed in a wide array of both
component and full-body test conditions for which human response is
known and was found to be both qualitatively and quantitatively
congruent with human response corridors.
Improved instrumentation. The THOR-50M has both improved and
additional instrumentation compared to the HIII-50M. The thorax
instrumentation measures the three-dimensional deformation of the rib
cage at four locations. The abdomen is also designed with a multi-point
measurement system that monitors three-dimensional deformation of the
abdomen at two locations. The upper leg includes an acetabulum load
cell in the pelvis to measure load transfer from the femur to the hip.
The lower leg has extensive instrumentation to support injury risk
calculation.
Improved injury prediction. The biofidelity of the THOR-50M,
combined with its extensive instrumentation, provides an enhanced
capability to measure expected human response and predict injury.
Injury criteria and injury risk functions, which relate instrumentation
measurements to a predicted risk of human injury, have been developed
for the head, neck, chest, abdomen, pelvis, upper leg, and lower leg of
the THOR-50M.\34\ These include injury criteria analogous to those
currently specified for the HIII-50M in FMVSS No. 208 as well as injury
criteria that are not currently specified for the HIII-50M in FMVSS No.
208. We believe this enhanced injury prediction capability will
translate into restraint system designs that have the potential to
enhance occupant protection. NHTSA and others, including vehicle
manufacturers, have already taken advantage of these capabilities in
the research arena.
---------------------------------------------------------------------------

\34\ Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E.,
Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD.
<a href="http://Regulations.gov">Regulations.gov</a> Docket ID NHTSA-2019-0106-0008, available at:
<a href="https://www.regulations.gov/document/NHTSA-2019-0106-0008">https://www.regulations.gov/document/NHTSA-2019-0106-0008</a>.
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Improved evaluation of vehicle performance. These enhancements
allow the THOR-50M to better differentiate the performance of different
vehicles and restraint systems. The more sophisticated measurement
capabilities of an advanced ATD are better suited to develop and test
more sophisticated and highly tunable contemporary restraint systems
with features such as multi-stage air bags and force-limiting/
pretensioning seat belts. Motor vehicle manufacturers and restraint
suppliers have already used the THOR-50M to evaluate vehicle
crashworthiness and develop occupant protection countermeasures.
Numerous conference and journal articles describing the use of the
THOR-50M have been published. For example, in a study examining the
performance of different restraint systems in frontal impact sled tests
using both the THOR-50M and HIII-50M, the THOR-50M was found to be more
sensitive to the restraint conditions, as it was able to differentiate
between both crash severity and restraint performance.\35\ Another
study investigated a novel air bag system with three inflated chambers
with a connected sail panel to promote earlier engagement with the
occupant and prevent lateral motion and head rotation; sled testing
using the THOR-50M demonstrated a reduction in brain injury risk due to
head angular velocity, as quantified using the Brain Injury Criterion
(BrIC).\36\ Other studies have also implemented the THOR-50M to assess
and develop restraint systems.\37\
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\35\ Sunnev[aring]ng, C., Hynd, D., Carroll, J., Dahlgren, M.,
``Comparison of the THORAX Demonstrator and HIII Sensitivity to
Crash Severity and Occupant Restraint Variation,'' Proceedings of
the 2014 IRCOBI Conference, Paper No. IRC-14-42, 2014.
\36\ Hardesty, J. (2021). Next-Generation Passenger Airbag. SAE
Government-Industry Digital Summit (oral only).
\37\ See also, e.g., Hu, J., Reed, M. P., Rupp, J. D., Fischer,
K., Lange, P., & Adler, A. (2017). Optimizing seat belt and airbag
designs for rear seat occupant protection in frontal crashes (No.
2017-22-0004). SAE Technical Paper; Eggers, A., Eickhoff, B.,
Dobberstein, J., Zellmer, H., Adolph, T. (2014). Effects of
Variations in Belt Geometry, Double Pretensioning and Adaptive Load
Limiting on Advanced Chest Measurements of THOR and Hybrid III.
Proceedings of the 2014 IRCOBI Conference, Paper No. IRC-14-40; Hu,
J., Fischer, K., Schroeder, A., Boyle, K., Adler, A., & Reed, M.
(2019, October). Development of oblique restraint countermeasures
(Report No. DOT HS 812 814). Washington, DC: National Highway
Traffic Safety Administration. Available at: <a href="https://rosap.ntl.bts.gov/view/dot/44143">https://rosap.ntl.bts.gov/view/dot/44143</a>.
---------------------------------------------------------------------------

Adoption of the THOR-50M in Europe

In 2013, the European Commission (EC) issued a final report
detailing the need for a new crash test dummy as a means to implement
regulatory requirements for new vehicle safety technologies,
particularly those technologies that reduce thorax injuries in frontal
crashes.\38\ At the time, the

[[Page 61901]]

THOR-50M was envisioned as the best evaluation tool for this purpose.
In 2015, United Nations Economic Commission for Europe (UNECE)
Regulation No. 137 (R137) went into effect. R137 specifies a 50 km/h,
full-width rigid barrier frontal impact test with driver and passenger
HIII-50M and HIII-5F dummies respectively. One objective of the
regulation was to encourage better restraint systems across a wider
range of collision severities.\39\
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\38\ European Commission, Seventh Framework Programme, THORAX
Project Final Report, Thoracic injury assessment for improved
vehicle safety, 1/7/2013.
\39\ Seidl, M., Edwards, M., Barrow, A., Hynd, D., & Broertjes,
P. (2017). The Expected Impact of UN Regulation No. 137 Tests on
European Cars and Suggested Test Protocol Modifications to Maximise
Benefits. In 25th International Technical Conference on the Enhanced
Safety of Vehicles (ESV).
---------------------------------------------------------------------------

In 2017, an ECE-funded study found that the R137 condition and
dummy diversity were not sufficiently different to existing UN
Regulation No. 94 (R94) to force improvements in restraint systems. R94
involves a 56 km/h frontal offset test which also prescribes the HIII-
50M in the driver and right front seat. To deliver the expected
benefits, the 2017 final report recommended implementation of the THOR-
50M in R137 as a replacement for the HIII-50M.\40\ The THOR-50M was
recognized as being more biofidelic in its representation of thoracic
response and prediction of thorax injuries, which are the key serious
and fatal injury types in full-width collisions targeted by R137.
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\40\ Seidl M, Hynd D, McCarthy M, Martin P, Hunt R, Mohan S,
Krishnamurthy V and O'Connell S: TRL Ltd. (2017). In depth cost-
effectiveness analysis of the identified measures and features
regarding the way forward for EU vehicle safety, Final Report, ISBN
978-92-79-68704-4, European Commission, 08-31-2017.
---------------------------------------------------------------------------

In 2018, the EC published a report on the cost-effectiveness and
the number of future injuries and fatalities that could be prevented at
a European level for different sets of vehicle safety measures.\41\
Several new sets of safety measures were considered for mandatory
implementation in new vehicles starting from 2022. This included the
introduction of the THOR-50M into R137. The THOR-50M was considered for
inclusion in a program titled ``Full-width Frontal Occupant Protection
with THOR (FFW-THO),'' which would lower injury criteria thresholds to
encourage implementation of adaptive restraints. It was envisioned that
the implementation of the THOR-50M would result in an initial cost of
16 Euros per vehicle, for vehicles that currently comply with UN
Regulation No. 137 with Hybrid III ATDs but not with THOR-50M ATDs. It
was estimated that vehicles that comply with FFW-THO would provide a 6%
increase in effectiveness in protecting against serious injuries
compared to vehicles that comply with R137 alone.
---------------------------------------------------------------------------

\41\ Seidl, M., Khatry, R., Carroll, J., Hynd, D., Wallbank, C.,
Kent, J. (2018) Cost-effectiveness analysis of Policy Options for
the mandatory implementation of different sets of vehicle safety
measures--Review of the General Safety and Pedestrian Safety
Regulations, Technical Annex to GSR2 report SI2.733025.
---------------------------------------------------------------------------

In 2019, the EC presented work priorities to WP.29 \42\ for 2019-
2021 for UNECE activities. An amendment to introduce the THOR-50M into
R137 was included. The target date for a WP.29 vote was listed as Q4/
2021.\43\ In 2020, Japan and the EC jointly initiated discussions
within WP.29 to establish a priority for the new task. In preparation
for an eventual adoption into R137, the E.C. commissioned TRL
(Transport Research Laboratory, UK) \44\ to conduct a survey of various
stakeholders on the readiness of the THOR-50M. ATD manufacturers, crash
test laboratories, and crash safety research laboratories were
consulted. The results of the survey are contained within Annex 7 of a
broader report on general safety regulations, published by the E.C. in
2021.\45\ In the E.C. report, there are a number of recommendations
based on stakeholder feedback. They include revisions to the dummy
design and qualification procedures that may be needed prior to
adopting THOR-50M into M.R. 1 \46\ and R137. Most stakeholders
recommended the formation of either an Informal Working Group or a
Technical Evaluation Group under the umbrella of UNECE WP.29 to co-
ordinate this activity. As of May 2023, a WP.29 working group has yet
to be established and timelines for amendments to R137 and M.R. 1 are
undetermined. The areas for further investigation identified in Annex 7
are discussed in this NPRM.
---------------------------------------------------------------------------

\42\ This was a thrice-annual briefing on the regulatory status
within the various working parties under WP.29's World Forum for
Harmonization of Vehicle Regulations, including the status of R137
under the Working Party for Passive Safety (GRSP).
\43\ WP.29-177-18, 177th WP.29, 12-15 March 2019, EU Work
priorities for 2019-2021 for UNECE activities.
\44\ TRL serves as an independent advisory to the E.C. TRL's
report was performed under contract with the European Commission
(E.C.), who sought to update the General Safety Regulation for
Europe to include new and developing technologies with the aim of
reducing Europe's annual road fatalities. The report reflects TRL's
recommendations for consideration by the E.C.
\45\ General Safety Regulation: Technical study to assess and
develop performance requirements and test protocols for various
measures implementing the new General Safety Regulation, for
accident avoidance and vehicle occupant, pedestrian and cyclist
protection in case of collisions, Final Report, March 2021,
Publications Office of the EU (europa.eu)), ISBN 978-92-76-08556-0,
DOI 10.2873/499942, Catalogue number, ET-04-19-467-EN-N. <a href="https://op.europa.eu/en/publication-detail/-/publication/6987b729-a313-11eb-9585-01aa75ed71a1/language-en/format-PDF/source-217672351">https://op.europa.eu/en/publication-detail/-/publication/6987b729-a313-11eb-9585-01aa75ed71a1/language-en/format-PDF/source-217672351</a> (last
accessed 5/25/2023).
\46\ Mutual Resolution No. 1 (M.R.1) of the 1958 and the 1998
Agreements. Concerning the description and performance of test tools
and devices necessary for the assessment of compliance of wheeled
vehicles, equipment and parts according to the technical
prescriptions specified in Regulations and global technical
regulations, ECE/TRANS/WP.29/1101, 10 January 2013.
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Although the ECE has not yet officially adopted the THOR-50M, the
European New Car Assessment Programme (Euro NCAP) has been rating
vehicles using the dummy. Euro NCAP has implemented a moving
progressive deformable barrier (MPDB) frontal impact testing protocol
with a THOR-50M in the driver's seat.\47\ The THOR-50M used by Euro
NCAP is specified in Technical Bulletin 026 (TB026) \48\ ``THOR
Specification and Certification.''TB026 explicitly adopts--with some
variations--NHTSA's 2018 technical data package (i.e., the 2018 drawing
package,\49\ qualification procedures,\50\ and PADI \51\). The
variations to the 2018 technical data package are relatively limited.
For example, TB026 specifies an onboard (in-dummy) data acquisition
system and a variation to the adjustable spine to facilitate data
acquisition system (DAS) installation; minor deviations in the shoulder
assembly; and the use of the HIII-50M lower legs. These modifications
are discussed in more detail in the relevant sections of the preamble
and are summarized in Section IX, Consideration of alternatives.
NHTSA's understanding is that no regulatory authorities or third-party
vehicle rating programs other than Euro NCAP currently specify the
THOR-50M for use in vehicle crash tests.
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\47\ European New Car Assessment Programme (2022). MPDB Frontal
Impact Testing Protocol, Version 1.1.3, available at: <a href="https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/">https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/</a>.
\48\ European New Car Assessment Programme (2023). THOR
Specification and Certification, Version 1.3, available at: <a href="https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/">https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/</a>.
\49\ Sec. 1.1.
\50\ Sec. 2.1.
\51\ Sec. 3.1.
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Motor vehicle and equipment manufacturers' interest in the design
and operation of the THOR-50M has been heightened since the dummy was
introduced into Euro NCAP and plans for R137 were announced.
Discussions are taking place within International Standards
Organization (ISO) Technical Committee 22 (Road Vehicles), Sub-
Committee 36 (Safety and impact testing), Working Group 5
(Anthropomorphic test devices) for

[[Page 61902]]

modifications suggested by manufacturers. With no defined European
entity to maintain configuration control, ISO has enlisted Humanetics
Innovative Solutions, Inc. (Humanetics) to investigate its change
recommendations directly. In particular, discussions have taken place
regarding modifications to the shoulder pad and rib guide. These
modifications are discussed in the relevant sections of the NPRM.

Need for This Rulemaking

NHTSA expects a variety of benefits from incorporating the THOR-50M
in Part 572. The THOR-50M is an advanced dummy with many advantages
over existing dummies with respect to biofidelity, instrumentation, and
injury prediction. NHTSA believes that the THOR-50M's enhancements will
lead to more effective restraint system designs and more informative
comparisons of the safety of different vehicles. Euro NCAP has adopted
it, the ECE is considering it for use in R137, and it is likely being
used by vehicle and restraint manufacturers for testing, research, and
development. Therefore, we believe vehicle manufacturers would choose
to certify new vehicles using the THOR-50M if given the option, because
this would enable manufacturers to streamline testing by using the same
dummy for research and development and to verify compliance and vehicle
ratings. NHTSA is therefore also considering a proposal to amend FMVSS
No. 208 to give vehicle manufacturers the option of selecting the THOR-
50M for use in belted and unbelted crash testing instead of the HIII-
50M.\52\
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\52\ FMVSS No. 208 THOR-50M Compliance Option (RIN 2127-AM21),
Fall 2023 Unified Agenda of Regulatory and Deregulatory Actions;
Department of Transportation, available at <a href="https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21">https://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202304&RIN=2127-AM21</a>. This
rulemaking would propose injury assessment reference values for the
THOR-50M comparable to the IARVs currently specified for the HIII-
50M.
---------------------------------------------------------------------------

There would be other benefits as well. For instance, the THOR-50M
is well-suited for the types of new seating configurations brought on
by vehicles with Automated Driving Systems (ADS). NHTSA is developing
an adaptation of the THOR-50M that is better suited for reclined
postures which may be prevalent among ADS occupants.\53\ NHTSA's test
dummies are also used in a range of applications beyond FMVSS
compliance testing--such as NCAP testing, standards and regulations in
other transportation modes, and research. While the purpose of Part 572
is to describe the anthropomorphic test devices that are to be used for
compliance testing of motor vehicles and motor vehicle equipment with
motor vehicle safety standards,\54\ it also serves as a definition of
the ATD for other purposes, such as consumer information crash testing,
standards and regulations in other transportation modes, and research.
As such, it would be to the benefit of government, academia, and the
multi-modal transportation industry to include a definition of the
THOR-50M ATD in Part 572.\55\
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\53\ Forman, J., Caudillo-Huerta, A., McMahon, J., Panzer, M.,
Marshall, W., Winter, D., Dyer, M., Lemmen, P. (2021). Modifications
to the THOR-50M for Improved Usability in Reclined Postures--Update
and Preliminary Findings. 2021 SAE Government-Industry Digital
Summit, available at: <a href="https://www.nhtsa.gov/node/103691">https://www.nhtsa.gov/node/103691</a>. The
adaptation to the THOR-50M design for use in reclined seating
environments is outside of the scope of this Part 572 NPRM.
\54\ 49 CFR 572.1.
\55\ For example, American Public Transportation Association
standard APTA PR-CS-S-018-13 Rev. 1 describes the use of a THOR ATD
in the testing of fixed workstation tables in passenger rail cars.
American Public Transportation Association. (2015, October). Fixed
Workstation Tables in Passenger Rail Cars. PR-CS-S-018-13, Rev. 1.
Washington, DC, available at: <a href="https://www.apta.com/wp-content/uploads/Standards_Documents/APTA-PR-CS-S-018-13-Rev-1.pdf">https://www.apta.com/wp-content/uploads/Standards_Documents/APTA-PR-CS-S-018-13-Rev-1.pdf</a>.
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III. Design, Construction, and Instrumentation

In this section we discuss the anthropometry, design, construction,
and instrumentation of the THOR-50M.

A. Anthropometry

The THOR-50M is a physical model of a 50th percentile male motor
vehicle occupant. It is intended for use in the development and
evaluation of vehicle safety countermeasures and vehicle safety
performance in frontal crash tests. To ensure that the dummy responds
in a human-like manner in a vehicle crash environment, it is necessary
that the size and shape of the dummy, referred to as anthropometry,
provide an accurate representation of a mid-sized male. The
anthropometry of the THOR-50M is based on a study by the University of
Michigan Transportation Research Institute that documented the
anthropometry of a mid-sized (50th percentile in stature and weight)
male occupant in an automotive seating posture (AMVO
study).56 57 This study defines an average male as 76.57 kg
(168.8 lb) in weight with a standing height of 175.1 cm (68.9 in). The
AMVO study is currently internationally accepted as the standard
anthropometry for the 50th percentile male ATD. The THOR-50M has a mass
of 77.37 kg (170.6 lb) and a seated height of 101.8 cm (40.2 in). The
standing height of the ATD cannot be measured since the pelvis does not
allow a full standing posture; however, since it was developed using
the AMVO body segment geometry and seated anthropometry, it is assumed
that the stature of the THOR-50M is also 175.1 cm.
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\56\ Schneider, L.W., Robbins, D.H., Pflug, M.A., Snyder, R. G.,
``Development of Anthropometrically Based Design Specifications for
an Advanced Adult Anthropomorphic Dummy Family; Volume 1-Procedures,
Summary Findings and Appendices,'' U.S. Department of
Transportation, DOT-HS-806-715, 1985.
\57\ Robbins, D.H., ``Development of Anthropometrically Based
Design Specifications for an Advanced Adult Anthropomorphic Dummy
Family; Volume 2-Anthropometric Specifications for mid-Sized Male
Dummy; Volume 3- Anthropometric Specifications for Small Female and
Large Male Dummies,'' U.S. Department of Transportation, DOT-HS-806-
716 & 717, 1985.
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The THOR-50M is consistent with the AMVO anthropometry. NHTSA
compared the dimensions of a representative dummy (S/N 9798) with the
AMVO target dimensions (Table 1).\58\ The AMVO procedure originally
used to collect measurements from volunteers was adapted to collect the
same or similar measurements on the THOR-50M.\59\ Most of these
measurements were taken with the THOR-50M seated on the AMVO bench,
which has an angled seat and backrest. One adaptation was necessary to
collect leg measurements on the AMVO bench: the THOR-50M has an
integrated molded shoe that cannot be separated from its foot, while
the AMVO data were collected on barefoot volunteers. To remedy this
situation, the THOR-50M measurements were recorded after removing the
entire molded shoe assembly and positioning the center of the ankle
joint at the same location as the AMVO ankle landmark. Another
adaptation was that four of the measurements were collected with the
THOR-50M seated on a 90-degree bench, as specified on drawing 472-0000,
Sheet 4. NHTSA also compared

[[Page 61903]]

the body segment masses specified in the proposed THOR drawing package
(472-0000, Sheet 5) with the AMVO body segment masses (Table 2), and
the masses were also consistent.
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\58\ A THOR-50M unit is a collection of serialized parts that
can be swapped out with other dummies, so is not considered a
``serialized'' dummy. Indeed, many of the subassemblies that were
part of S/N 9798 when NHTSA took these measurements were
subsequently swapped out of the dummy. See Section VII.A.
\59\ These AMVO measurements were collected as an assessment of
anthropometry; it is understood that there is variation in initial
position and measurement methodology that prevents the use of such
measurements as a repeatable dimensional assessment. In practice, a
simplified set of dimensional requirements are put in place as a
check for overall part fit, tolerance stack, and to ensure that the
dummy is assembled correctly. These requirements are specified on
drawing 472-0000, Sheet 4, and are collected following the
``Procedures for Measuring External Dimensions'' section of the
PADI.

Table 1--THOR-50M Anthropometry Compared to AMVO
------------------------------------------------------------------------
AMVO target
Dimensions (all measurements in (Robbins et al THOR-50M S/N
centimeters) 1983) 9798
------------------------------------------------------------------------
Height of top of head to floor.......... 100.3 101.8
Height of shoulder to floor............. 72.1 74.2
H-point to knee joint distance (note 1). 43.2 42.3
Buttock to knee end distance (note 2)... 59.3 62.0
Height of knee from floor............... 45.3 47.0
Head circumference...................... 57.1 58.7
Head top-chin distance.................. 19.7 22.9
Head breadth............................ 15.8 15.3
Chest circumference..................... 101.1 95.5
Chest breadth........................... 34.9 30.9
Chest depth (note 3).................... 22.7 22.4
Abdomen circumference................... 91.3 99.0
Abdomen breadth......................... 32.5 32.5
Abdomen depth (note 2).................. 26.9 29.8
Pelvis breadth.......................... 38.5 38.8
Thigh max circumference................. 57.9 56.8
Thigh max breadth....................... 19.4 17.1
Mid thigh circumference................. 50.4 56.0
Mid thigh breadth....................... 15.5 17.8
Calf circumference...................... 37.3 37.5
Calf breadth............................ 11.0 9.1
Calf depth.............................. 11.8 11.9
------------------------------------------------------------------------
\1\ THOR-50M specified on 472-0000, Sh. 4, measurement F (Knee Pivot to
Hip Pivot) as seated upright on a 90-degree bench.
\2\ THOR-50M and AMVO measured as seated upright on a 90-degree bench.
\3\ THOR-50M specified on 472-0000, Sh. 4, measurement I (Rib #3 depth)
as seated upright on a 90-degree bench without jacket installed.

Table 2--THOR-50M Body Segment Masses Compared to AMVO
------------------------------------------------------------------------
AMVO target THOR-50M
Body segment masses (all measurements in (Robbins et al specification
kilograms) 1983) *
------------------------------------------------------------------------
Head.................................... 4.137 4.501
** (4.55)
Neck.................................... 0.965 2.363
Thorax.................................. 23.763 23.517
Lower Abdomen........................... 2.365 2.664
Pelvis.................................. 11.414 15.229
Upper Arm, Left or Right................ 1.769 1.701
Lower Arm with Hand, Left or Right...... 2.022 2.227
Upper Leg, Left or Right................ 8.614 5.618
Lower Legs, Left or Right............... 3.587 3.396
Feet, Left or Right including shoe...... *** 1.551 1.604
-------------------------------
Total Weight........................ 76.562 77.366
------------------------------------------------------------------------
* Listed on Drawing No. 472-0000, Sh. 5.
** Mass reported in Melvin JW, Weber, K. ``Task B Final Report: Review
of Biomechanical Impact Response and Injury in the Automotive
Environment,'' U.S. Department of Transportation, DOT-HS-807-042,
1985. The AMVO target is believed to be too low.
*** This adds the mass of a size 11 Oxford shoe (0.57 kg) specified for
use in FMVSS No. 208 for the HIII-50M) to the AMVO specification of
0.981 kg so as to be comparable to the THOR's foot-within-a-molded-
shoe mass.

B. Technical Data Package

The construction of the THOR-50M is similar to other ATDs currently
defined in Part 572, with a metallic frame largely covered in urethane
and/or vinyl representing flesh; body segments connected by
translational and rotational joints; and deformable rubber or foam
elements to prevent hard contact between metallic surfaces and to
provide human-like impact response. The kinematic and dynamic
biomechanical performance requirements of the THOR-50M were developed
based on post-mortem human subject (PMHS) and volunteer response data,
described in Section IV, Biofidelity.
The THOR-50M that we are proposing in this NPRM is the version
defined in the 2023 technical data package (consisting of two-
dimensional engineering drawings and a Parts list; procedures for
assembly, disassembly, and inspection (PADI); and qualification
procedures). The 2023 technical data package also includes an addendum
with the drawings and drawing/parts list for an alternate configuration
with an in-dummy data acquisition system, as discussed in Section
III.N, Data Acquisition System. It is anticipated that, upon
finalization of this proposal,

[[Page 61904]]

the in-dummy DAS drawings will be fully integrated within the relevant
technical data package components. The technical data package is
summarized in Table 3. For these documents, the NPRM cites to the
document location in the research docket. NHTSA is not placing copies
of these documents in the rulemaking docket, in order to avoid
potential confusion from having identical documents docketed at
different times in different dockets. However, NHTSA intends these to
be included as part of the rulemaking record. A memo explaining this is
also being included in the rulemaking docket. In addition, as noted in
the background section, NHTSA began publishing the technical data
package to its website starting in 2015. The 2023 technical data
package updates the 2018 technical data package. These updates were
made to address typographical errors, improve clarity, and add
alternative design elements. Table 4 summarizes these updates.

Table 3--THOR-50M Technical Data Package
------------------------------------------------------------------------
Title Link
------------------------------------------------------------------------
THOR 50th Percentile Male with https://www.regulations.gov/
Alternate Shoulders Frontal Crash Test document/NHTSA-2019-0106-0013.
Dummy Drawings, External Dimensions,
and Mass Properties.
*THOR-50M DAS Integration Kit Drawings, https://www.regulations.gov/
April 2023. document/NHTSA-2019-0106-0019.
*Parts List, THOR-50M DAS Integration https://www.regulations.gov/
Kit, April 2023. document/NHTSA-2019-0106-0018.
Parts List, THOR 50th Percentile Male https://www.regulations.gov/
Frontal Crash Test Dummy with document/NHTSA-2019-0106-0015.
Alternate Shoulders.
THOR 50th Percentile Male (THOR-50M): https://www.regulations.gov/
Procedures for Assembly, Disassembly, document/NHTSA-2019-0106-0017.
and Inspection (PADI): June 2023.
THOR 50th Percentile Male (THOR-50M) https://www.regulations.gov/
Qualification Procedures and document/NHTSA-2019-0106-0010.
Requirements, April 2023.
------------------------------------------------------------------------
* The DAS Integration Kit drawings and drawing/parts list would not
themselves be incorporated by reference into Part 572. It is
anticipated that, upon finalization of this proposal, these documents
will be fully integrated within the relevant technical data package
components.

Table 4--Summary of Updates Made in the 2023 THOR-50M Technical Data
Package
------------------------------------------------------------------------
Technical Data Package
Element Revisions in 2023 Version
------------------------------------------------------------------------
Drawing Package.............. Includes drawings for alternate shoulder,
removal of notes suggesting that
qualification specifications supersede
drawing specifications, and changes to
correct typographical drawing errors.
Complete change log found in ``THOR-50th
Percentile Male with Alternate Shoulders
(THOR-50M w/ALT. SHOULDERS) Drawing
Revisions''.\60\
PADI......................... Minor typographical changes; complete
change log found in Section 20 of ``THOR
50th Percentile Male (THOR-50M)
Procedures for Assembly, Disassembly,
and Inspection (PADI)''.
Qualification Procedures..... Revised upper leg qualification test
mode, adjusted language to be more
prescriptive, removed unit conversions,
and corrected typographical errors.
Complete change log found in Appendix B
of ``THOR 50th Percentile Male (THOR-
50M) Qualification Procedures and
Requirements, April 2023''.
------------------------------------------------------------------------

Below we briefly discuss several aspects of the technical data
package in more detail.
---------------------------------------------------------------------------

\60\ See Table 5.
---------------------------------------------------------------------------

Engineering Drawings and Parts List
The engineering drawings and parts list specify the configuration
of the THOR-50M. Included in the drawings are the required dimensions
and tolerances, material properties, and component or material testing
requirements and associated specifications. In a few instances, the
drawings specify quasi-static tests and/or performance requirements for
individual parts (such as a compression or flexion test for a molded
part or subassembly); however, passing a specified performance (or
qualification) test is not an alternate criterion for accepting a part
that deviates from the drawing specifications.\61\ All instruments are
specified by corresponding SA572-xxx drawings.\62\ SA drawings are
included for associated mounts and hardware that are not otherwise
needed when the dummy is configured with a corresponding structural
replacement. Brand name call-outs are only used for parts and materials
that have widespread availability and are used for a wide variety of
non-ATD applications. It includes materials widely identified by their
tradenames, such as Teflon, Acetal, Lexan, and Nitinol. Call-outs are
also used for bonding agents, fasteners, and other items that are also
widely available for non-ATD applications.
---------------------------------------------------------------------------

\61\ In the drawings which were part of the August 2018
technical data package, several notes state that ``qualification
takes precedence over design.'' These notes were unintentionally
carried over from earlier drawing versions used during THOR-50M
development, and have since been removed. These are reflected in the
proposed 2023 technical data package. In cases where some
flexibility is allowed in order to meet the qualification
specification, a ``REF.'' prefix is added to specific dimensions or
material specifications.
\62\ This convention is used for all instruments on all Part 572
dummies. SA572 simply indicates that it is an instrument, and Sxx is
the next-in-line number assigned by NHTSA to the instrument. Some
load cells (and part numbers) are used on different Part 572 subpart
dummies. For THOR, this applies to SA572-S4 (accelerometer) which is
used on many other dummies.
---------------------------------------------------------------------------

In some instances, the drawing package permits two different part
or instrumentation configurations that are both fully specified. For
example, the head accelerometer mounting plate assembly drawing (472-
1200) calls out three different angular rate sensors (SA572-S56, SA572-
S57, or SA572-S58) which may be desired by the end user depending on
the implementation of the ATD.\63\ In the sections below on specific
body regions we discuss the proposed as well as alternate designs and
instrumentations that are not included in the proposed specifications
but which we are considering specifying in the final rule and on which
we are seeking comment. If NHTSA were to use the dummy for FMVSS
compliance testing, NHTSA could test with any alternative
configurations at its own discretion. Thus, the IARVs would have

[[Page 61905]]

to be met using a dummy with any permissible configuration.
Manufacturers are not required to test their products in any particular
manner, as long as they exercise due care that their products will meet
the requirements when tested by NHTSA under the procedures specified in
the standard, including the relevant dummy specified in Part 572.\64\
However, a manufacturer would not be able to claim that a vehicle fully
complies with a standard if it meets the standard's requirements in
only one of the dummy's configurations, but not the other.
---------------------------------------------------------------------------

\63\ Similar situations exist with currently federalized ATDs,
such as the HIII-10C, where either a chest slider pot or an IR-TRACC
is permissible.
\64\ See, e.g., 38 FR 12934, 12935 (May 17, 1973)
(``Manufacturers should understand that they are not required to
test their products in any particular manner, as long as they
exercise due care that their products will meet the requirements
when tested by the NHTSA under the procedures specified in the
standard.'').
---------------------------------------------------------------------------

In addition to the engineering drawings that would be incorporated
by reference, we are also providing supplemental documentation on the
form and function of the THOR-50M. These reference materials are
summarized in Table 5. These files would not be incorporated by
reference in Part 572 and would therefore not be part of the THOR-50M
specification. Instead, they are intended only for reference purposes
(e.g., to facilitate fabrication and inspection of parts with intricate
geometries).

Table 5--THOR-50M Design Reference Documentation
------------------------------------------------------------------------
Title Link
------------------------------------------------------------------------
THOR-50M Drawing Package--2D AutoCAD https://static.nhtsa.gov/nhtsa/
Jan 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20with%20Alternate%20Shoul
ders%20Jan%202023-
AutoCAD%20DWG%20Files.zip.
THOR-50M Drawing Package--3D Inventor https://static.nhtsa.gov/nhtsa/
Format Jan 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20with%20Alternate%20Shoul
ders%20Jan%202023-
Inventor%20Files.zip.
THOR-50M Drawing Package--3D STEP https://static.nhtsa.gov/nhtsa/
Format Jan 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20DAS%20Integration%20Kit-
3D%20STEP%20Files_April%202023
.zip.
THOR 50th Percentile Male with https://www.regulations.gov/
Alternate Shoulders Drawing Revisions, document/NHTSA-2019-0106-0014.
Jan 2023.
THOR-50M DAS Integration Kit--2D https://static.nhtsa.gov/nhtsa/
AutoCAD, April 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20DAS%20Integration%20Kit-
AutoCAD%20DWG%20Files_April%20
2023.zip.
THOR-50M DAS Integration Kit--3D STEP https://static.nhtsa.gov/nhtsa/
Format, April 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20DAS%20Integration%20Kit-
3D%20STEP%20Files_April%202023
.zip.
THOR-50M DAS Integration Kit--Inventor https://static.nhtsa.gov/nhtsa/
Format, April 2023. downloads/
THOR_50M_Drawing_Package/NPRM/
THOR-
50M%20DAS%20Integration%20Kit-
Inventor%20Files_April%202023.
zip.
------------------------------------------------------------------------

The THOR-50M used by Euro NCAP is specified in Technical Bulletin
026, ``THOR Specification and Certification.'' \65\ TB026 explicitly
adopts--with some deviations--the 2018 drawing package.\66\ These
deviations in TB026 include specification of an onboard (in-dummy) data
acquisition system and a variation to the adjustable spine to
facilitate DAS installation; minor deviations in the shoulder assembly;
and the use of the HIII-50M lower legs. These modifications are
discussed in more detail in the relevant sections of the preamble, and
are summarized in Section IX, Consideration of alternatives. Euro NCAP
TB026 specifies the 2018 drawing package, while this proposal specifies
the 2023 drawing package. However, given the differences described in
Table 4 above, this deviation is likely to be inconsequential. The
deviations TB026 makes to the 2018 drawing package are not accompanied
by engineering drawings, which may tend to lessen the dummy's overall
objectivity. Objectivity is a statutory necessity for ATDs in Part 572.
While the lack of accompanying drawings for these deviations may be
adequate for the Euro NCAP rating program, it could lead to a future
population of THOR-50M units that are sufficiently non-uniform as to
render them unsuited for FMVSS applications.
---------------------------------------------------------------------------

\65\ European New Car Assessment Programme (2023). THOR
Specification and Certification, Version 1.3, available at: <a href="https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/">https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/</a>.
\66\ Sec. 1.1.
---------------------------------------------------------------------------

PADI
The PADI provides step-by-step procedures on how to properly
assemble the dummy. This includes instructions on part alignment,
torque settings, wire routings, and other adjustments that are not
otherwise described in the engineering drawings. The PADI provides
explicit installation instructions for all instruments. Euro NCAP TB026
specifies the 2018 PADI,\67\ while this proposal specifies the 2023
PADI. However, the differences between the 2018 PADI and 2023 PADI are
primarily corrections to typographic errors, so this deviation is
likely to be inconsequential. In some instances, the drawing package
permits two different part or instrumentation configurations that are
(or will be in the final rule) both fully specified (for example, the
IR-TRACC and the S-Track for the chest instrumentation). The proposed
PADI does not currently contain installation instructions for the
optional parts (e.g. alternate shoulder) or instrumentation (e.g., the
S-Track). However, where multiple optional configurations are permitted
and installation differences are non-trivial, NHTSA anticipates
supplementing the PADI with such instructions in the final rule.
---------------------------------------------------------------------------

\67\ Sec. 3.1.
---------------------------------------------------------------------------

Qualification Procedures
The qualification procedures describe a series of impact tests
performed on a fully assembled dummy or sub-assembly. NHTSA has
established numeric bounds or acceptance intervals for the ATD
responses in these tests. The qualification procedures are discussed in
Section V.

[[Page 61906]]

Summary
NHTSA believes that the technical data package adequately describes
and would ensure the uniformity of the dummy. Upon finalization of this
proposal, a new subpart for the THOR-50M would be added to Part 572,
and the technical data package documents would be incorporated by
reference.
NHTSA seeks comment on whether the dummy is sufficiently specified
to ensure that dummies are uniform such that they will provide
repeatable and reproducible measurements. We also seek comment on
whether it would be useful to end-users of the dummy if NHTSA created a
list of suppliers used by NHTSA to obtain various parts and
instrumentation, and/or general specifications or operating
characteristics of a part (as provided by a manufacturer's
specification sheet). Such documentation would not be incorporated into
Part 572 but would be provided as a reference aid for users and could
be periodically updated by NHTSA.

C. Head and Face

The head of the THOR-50M is primarily constructed of a cast
aluminum skull covered in a urethane head skin. It includes two
features not seen on the HIII-50M: spring towers and a featureless
face. The spring towers are integral to the response of the head/neck
system, as they are the mounting location of the cables that represent
the musculature of the neck (described further in the following
section). The head is equipped with three uniaxial accelerometers and
three angular rate sensors at the head center of gravity (CG) to
measure translational acceleration and angular velocity, respectively.
The head also includes a biaxial tilt sensor which measures the quasi-
static orientation of the head for pre-test positioning purposes.
The face is constructed of an open-cell urethane foam sandwiched
between the head skin and the face load distribution plates. The
featureless face allows for more repeatable and reproducible
interactions with potential contact surfaces and meets enhanced
biomechanical response requirements which have not been implemented on
any existing ATDs. Additionally, the face can be configured with five
uniaxial load cells: left and right eye, left and right cheek, and
chin.\68\
---------------------------------------------------------------------------

\68\ These load cells have not been used in any tests currently
available in NHTSA's Vehicle or Biomechanics databases, and are
typically replaced with structural replacements during testing.
While the THOR-50M Qualification Procedure does include a face
impact test which would exercise the face load cells if installed,
there are currently no qualification specifications on face load
cell forces.
---------------------------------------------------------------------------

D. Neck

The neck of the THOR-50M is visibly and functionally different than
the ATDs currently defined in Part 572. While typical ATD designs use
only a pin joint between the base of the head and the upper neck load
cell, the THOR-50M neck is connected to the head via three separate
load paths: two cables (one anterior and one posterior) and a pin joint
between the base of the head and the upper neck load cell. These load
paths are independently instrumented, allowing the isolation of forces
and moments on the components representing bone and ligament from the
components representing muscles. This is expected to allow for improved
injury prediction for the cervical spine because the abbreviated injury
scale (AIS) 2+ injuries \69\ to the cervical spine in motor vehicle
crashes are most commonly fractures, so the ability to measure forces
and moments acting on the bones and ligaments separately from the
forces acting through the musculature allows a more accurate prediction
of these fractures.\70\
---------------------------------------------------------------------------

\69\ The Abbreviated Injury Scale (AIS) ranks individual
injuries by body region on a scale of 1 to 6: 1=minor,
2=moderate, 3=serious, 4=severe, 5=critical, and 6=maximum
(untreatable).
\70\ Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E.,
Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD.
Docket ID NHTSA-2019-0106-0008, available at: <a href="https://www.regulations.gov/document/NHTSA-2019-0106-0008">https://www.regulations.gov/document/NHTSA-2019-0106-0008</a>.
---------------------------------------------------------------------------

The biomechanical basis of the THOR-50M neck design is well-
established.71 72 The construction of the THOR-50M neck
allows the head to initially rotate relatively freely in the fore and
aft directions. This allows the head/neck assembly to demonstrate the
phenomenon known as head lag demonstrated by human volunteers in
restrained frontal loading conditions, where the rotation of the head
is delayed relative to the rotation of the neck.\73\ This phenomenon
results from the head initially translating forward with respect to the
base of the neck, which is attached to the restrained torso. The change
in angle of the head initially lags the change in angle of the line
between the head and the neck but catches up by the time of peak
excursion.
---------------------------------------------------------------------------

\71\ White RP., Zhoa Y., Rangarajan N., Haffner M., Eppinger R.,
Kleinberger M., ``Development of an Instrumented Biofidelic Neck for
the NHTSA Advanced Frontal Test Dummy,'' The 15th International
Technical Conference on the Enhanced Safety of Vehicles, Paper No.
96-210-W-19, 1996.
\72\ Hoofman, M., van Ratingen, M., and Wismans, J.,
``Evaluation of the Dynamic and Kinematic Performance of the THOR
Dummy: Neck Performance,'' Proceeding of the International
Conference on the Biomechanics of Injury (IRCOBI) Conference, pp.
497-512, 1998.
\73\ Thunnissen, J., Wismans, J., Ewing, C.L., Thomas, D.J.
(1995) Human Volunteer Head-Neck Response in Frontal Flexion: A New
Analysis. 39th Stapp Car Crash Conference, SAE Paper # 952721.
---------------------------------------------------------------------------

The instrumentation in the neck assembly includes spring load cells
which measure the compression at the anterior and posterior spring
locations, six-axis load cells at the top and base of the neck to
measure the forces and moments developed at these locations, and a
rotary potentiometer at the occipital condyle pin to measure the
relative rotation between the head and top of the neck. Due to the
multiple load paths of the neck, comparing THOR-50M neck forces and
moments to traditional single-load-path ATD designs is not
straightforward; the THOR-50M instrumentation would require post-
processing \74\ to represent the total neck forces and moments in order
to compare to the upper neck load cell measurements of a HIII-50M ATD.
However, as described in the THOR-50M Injury Criteria Report,\75\ post-
processing of the neck for calculation of neck injury risk is not
necessary.
---------------------------------------------------------------------------

\74\ GESAC, Inc (2005). Users Manual: THOR Instrumentation Data
Processing Program, Version 2.3; Appendix C: Procedure for
Calculating Head Loads at the Occipital Condyle from Neck Load Cell
Measurements. National Highway Traffic Safety Administration.
Available at: <a href="https://one.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/THORTEST.zip">https://one.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/THORTEST.zip</a>.
\75\ Craig, M., Parent, D., Lee, E., Rudd, R., Takhounts, E.,
Hasija, V. (2020). Injury Criteria for the THOR 50th Male ATD.
Docket ID NHTSA-2019-0106-0008, available at: <a href="https://www.regulations.gov/document/NHTSA-2019-0106-0008">https://www.regulations.gov/document/NHTSA-2019-0106-0008</a>.
---------------------------------------------------------------------------

E. Chest

Throughout the development of the THOR-50M ATD, specific attention
was given to the human-like response and injury prediction capability
of the chest. Below we discuss the design and instrumentation of the
THOR-50M chest.
1. Design
The THOR-50M's rib cage geometry is more realistic than the HIII-
50M because the individual ribs are angled downward to better match the
human rib orientation.\76\ Biomechanical response requirements were
selected to ensure human-like behavior in response to central chest
impacts, oblique chest impacts, and steering rim impacts to the

[[Page 61907]]

rib cage and upper abdomen.\77\ Better chest anthropometry means that
the dummy's interaction with the restraint system is more
representative of the interaction a human would experience.
---------------------------------------------------------------------------

\76\ Kent, R., Shaw, C.G., Lessley, D.J., Crandall, J.R. and
Svensson, M.Y, ``Comparison of Belted Hybrid III, THOR, and Cadaver
Thoracic Responses in Oblique Frontal and Full Frontal Sled Tests,''
Proc. SAE 2003 World Congress. Paper No. 2003-01-0160, 2003.
\77\ National Highway Traffic Safety Administration,
``Biomechanical Response Requirements of the THOR NHTSA Advanced
Frontal Dummy, Revision 2005.1,'' Report No: GESAC-05-03, U.S.
Department of Transportation, Washington, DC, March 2005. [<a href="http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf">http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf</a>.
---------------------------------------------------------------------------

The design of the THOR-50M includes a part known as a rib guide
(472-3310) which is intended to prevent excessive downward motion of
the anterior thorax during an impact. The rib guide is attached to the
shoulder, and when there is downward motion of the ribs, the bottom of
the rib damping material on rib #1 (the superior-most rib in the torso,
472-3310) can contact the top of the rib guide. Over time, this can
result in an indent in the rib damping material. This indent has been
observed on NHTSA-owned THOR-50M ATDs, but it has not been a concern as
this is a sign of the rib guide performing its intended function. While
this indent is not included on the drawing package, it is understood
that an indent is acceptable as long as the qualification
specifications (specifically, those of the upper thorax and lower
thorax) are met, and it is not so deep that it allows metal-to-metal
contact between the rib guide and the steel of the rib.
While Euro NCAP TB026 adopts the chest specified in the 2018
drawing package without any modifications, NHTSA is aware of two
potential changes that have been discussed. Both of these changes
appear to be intended to help ensure that the dummy is able to meet the
upper thorax qualification response requirements. (The TB026 upper
thorax qualification response requirements differ in a few ways from
the proposed qualification requirements. This is discussed in more
detail in Section V, Qualification Tests.)
The first change that has been discussed is a shorter rib guide.
Humanetics Innovative Solutions, Inc. (Humanetics) reported to ISO WG5
(in June 2020) that while the indent on the damping material has been a
known issue since the THOR-NT, it has led to concerns because it leads
to issues meeting the Euro NCAP upper thorax qualification response
requirements (specifically, the Z-axis upper rib deflection
requirement) on a consistent basis. Humanetics has therefore suggested
the use of a new, shorter rib guide which would allow more Z-axis
deflection--primarily in the upper thorax qualification test, but
presumably in other impact scenarios as well.
The second change is an additional rib performance specification.
NHTSA is aware of a presentation made by the Japanese Automobile
Manufacturers Association (in June 2020) to ISO WG5 describing an
additional rib performance specification (i.e., that would be specified
in the drawing package) geared towards more consistently meeting the
TB026 upper thorax qualification response requirements. The
presentation included a procedure for an individual rib test using the
same apparatus as the rib drop test for the ES-2re 50th percentile
adult male side impact test dummy.\78\ It noted data showing that the
stiffness of the individual rib in the drop test was correlated with
the thoracic impact response in the upper thorax qualification test
condition.
---------------------------------------------------------------------------

\78\ 49 CFR 572.185(b) Individual rib drop test.
---------------------------------------------------------------------------

NHTSA has tentatively decided not to implement either change.
NHTSA's qualification testing of the dummy did not reveal any issues
with meeting the proposed upper thorax qualification requirements, so
we do not believe such changes are necessary. Moreover, before
implementing the rib guide modification, it could be necessary to
evaluate whether it would influence the dummy's response in biofidelity
or thorax injury criteria test conditions. We do note, however, that
the additional rib performance specification could be a useful way for
ATD manufacturers to ensure that the fabricated ribs will result in an
upper thorax qualification response consistent with upper thorax
qualification specifications.
We seek comment on these issues. In particular, NHTSA requests
comment from THOR-50M users who have evaluated alternative rib guide
designs and have data to support equivalence of durability,
repeatability and reproducibility, and equivalence of response in
qualification, biofidelity, injury criteria, and vehicle crash test
conditions.
2. Instrumentation
The THOR-50M is capable of measuring detailed information about how
the chest responds in a crash. While the HIII-50M can measure chest
deflection at only a single point (the sternum), the THOR-50M measures
chest deflections at four points. This is useful because thoracic
trauma imparted to restrained occupants does not always occur at the
same location on the rib cage for all occupants in all frontal
crashes.\79\ Measuring deflection from multiple locations has been
found to improve injury prediction,\80\ and can improve the assessment
of thoracic loading in a vehicle environment with advanced occupant
restraint technologies.\81\ While the HIII-50M measures the one-
dimensional deflection at a single point, the THOR-50M can measure the
three-dimensional position time-history for four points on the anterior
rib cage relative to the local spine segment of rib origination, with
two points on the upper chest, and two points on the lower chest.
Between the upper and lower thorax instrumentation attachment points is
a flexible joint (the Upper Thoracic Spine Flex Joint), so the
reference coordinate system for the upper and lower thorax 3D motion
measurements can change dynamically during a loading event. This
instrumentation, coupled with its thoracic biofidelity,\82\ provides
the THOR-50M ATD with the ability to better predict thoracic injuries
and to potentially drive more appropriate restraint system
countermeasures.\83\
---------------------------------------------------------------------------

\79\ Morgan, R.M., Eppinger, R.H., Haffner, M.P., Yoganandan,
N., Pintar, F.A., Sances, A., Crandall, J.R., Pilkey, W.D., Klopp,
G.S., Kallieris, D., Miltner, E., Mattern, R., Kuppa, S.M., and
Sharpless, C.L., ``Thoracic Trauma Assessment Formulations for
Restrained Drivers in Simulated Frontal Impacts,'' Proc. 38th Stapp
Car Crash Conference, pp. 15-34. Society of Automotive Engineers,
Warrendale, PA., 1994.
\80\ Kuppa, S., Eppinger, R., ``Development of an Improved
Thoracic Injury Criterion,'' Proceedings of the 42nd Stapp Car Crash
Conference, SAE No. 983153, 1998 (data set consisting of 71 human
subjects in various restraint systems and crash severities).
\81\ Yoganandan, N., Pintar, F., Rinaldi, J., ``Evaluation of
the RibEye Deflection Measurement System in the 50th Percentile
Hybrid III Dummy.'' National Highway Traffic Safety Administration,
DOT HS 811 102, March 2009.
\82\ Parent, D., Craig, M., Ridella, S., McFadden, J.,
``Thoracic Biofidelity Assessment of the THOR Mod Kit ATD,'' The
23rd Enhanced Safety of Vehicles Conference, Paper No. 13-0327,
2013.
\83\ In addition to the deflection measurement system, the THOR-
50M can also be instrumented with a uniaxial sternum accelerometer,
triaxial accelerometers installed along the spine at the level of
T1, T6, and T12, and a five-axis (three forces, two moments) load
cell installed between the lumbar spine pitch change mechanism and
the lumbar spine flex joint at the approximate anatomical level of
T12. Clavicle loads cells can also be installed, but are not
included in the THOR-50M described in the 2023 drawing package.
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NHTSA is proposing to specify two deflection measurement devices,
either of which NHTSA could choose, at its option, for use in the THOR-
50M: the IR-TRACC and the S-Track.
IR-TRACC
The 2023 drawing package specifies a specific deflection
measurement device, the Infrared Telescoping Rod for Assessment of
Chest Compression (IR-

[[Page 61908]]

TRACC).\84\ The IR-TRACC improved on the previous deflection
measurement systems (CRUX--Compact Rotary Unit; DGSP--Double Gimbaled
String Potentiometer) in many ways. The 2023 drawing package specifies
six IR-TRACCs: four in the thorax and two in the abdomen.\85\ Each IR-
TRACC measures the absolute point-to-point distance along its length;
this is used in the calculation of thorax and abdomen compression. The
IR-TRACC is attached to two rotational potentiometers; this enables
measurement of the three-dimensional position of the anterior
attachment point at the rib or front of the abdomen relative to the
attachment point at the spine.
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\84\ Rouhana, S.W., Elhagediab, A.M., Chapp, J.J. ``A high-speed
sensor for measuring chest deflection in crash test dummies.''
Proceedings: International Technical Conference on the Enhanced
Safety of Vehicles. Vol. 1998, Paper No. 98-S9-O-15. National
Highway Traffic Safety Administration, 1998.
\85\ See SA572-S117 and SA572-S121.
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While NHTSA has generally been satisfied with the performance of
the IR-TRACC, the experience of NHTSA and other users with IR-TRACC-
equipped THOR-50Ms has revealed a few potential issues. Vehicle
manufacturers have raised several concerns about the performance and
durability of the IR-TRACC, such as having to frequently repair or
replace IR-TRACCs, and problems with the abdomen IR-TRACCs.\86\ And
during NHTSA-sponsored testing (particularly in the frontal oblique
crash test mode), NHTSA observed abrupt decreases in the IR-TRACC
voltage time-history.\87\ We believe this is noise (and not a signal)
because it occurs in all IR-TRACC voltage channels of a single ATD at
the same points in time. As explained later in this document (Section
VII.B.2) and in Appendix F to the preamble,\88\ NHTSA testing has shown
that once the IR-TRACC voltage signal is linearized, scaled, filtered,
and converted to three-dimensional deflection, this noise is no longer
evident. Nonetheless, this presents a risk of perceived or actual
inaccuracies in thoracic and abdominal injury prediction during crash
tests.
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\86\ Alliance of Automobile Manufacturers, Inc. (2016).
Technical Considerations Concerning NHTSA's Proposal to Rework the
Agency's New Car Assessment Program (NCAP). <a href="http://Regulations.gov">Regulations.gov</a> Docket
ID NHTSA-2015-0119-0313, available at: <a href="https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf">https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf</a>.
\87\ See Figure 1 in Hagedorn, A., Murach, M., Millis, W.,
McFadden, J., Parent, D., (2019). Comparison of the THOR-50M IR-
TRACC Measurement Device to an Alternative S-Track Measurement
Device. Proceedings of the Forty-Seventh International Workshop on
Human Subjects for Biomechanical Research.
\88\ NHTSA is placing a separate document, ``Supplemental
Technical Appendices to Preamble,'' in the docket for this
rulemaking.
---------------------------------------------------------------------------

S-Track
In 2016 NHTSA issued a request for proposals for commercially-
available devices capable of measuring the same or greater deflection
range (roughly 90 millimeters of deflection for the thorax and 120
millimeters of deflection for the abdomen) within the same packaging
space as the existing IR-TRACC devices.\89\ Only one device--the S-
Track--was identified. The S-Track, which is patented,\90\ is produced
by ATD-LabTech GmbH. (In 2022, Humanetics acquired ATD-LabTech.)
Subsequent to the request for proposal, NHTSA also became aware of two
additional deflection measurement devices: the KIR-TRACC, sold by
Kistler Group, and the Spiral Track, sold by JASTI. NHTSA does not know
whether these devices are congruent with the current THOR-50M parts and
SA-drawings that describe the configuration and installation of IR-
TRACCs. Because NHTSA became aware of these devices late in the
development process (and neither was identified in NHTSA's request for
proposals), they have not been considered for inclusion in the
proposal, although NHTSA is considering evaluating whether they would
be suitable instrumentation for the THOR-50M. Euro NCAP allows for
installation of the IR-TRACC, the S-Track, and the KIR-TRACC.\91\
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\89\ National Highway Traffic Safety Administration (2016). IR-
TRACC Direct Replacement Sensor. Solicitation Number DTNH2216Q00014,
available at <a href="https://sam.gov/opp/d505f6119f9a31bcdfa36607ed669e6b/view">https://sam.gov/opp/d505f6119f9a31bcdfa36607ed669e6b/view</a>.
\90\ Pheifer, G. (2020). U.S. Patent No. 10,713,974. Washington,
DC: U.S. Patent and Trademark Office.
\91\ European New Car Assessment Program (2022). Euro NCAP
Supplier List, Appendices I & II, October 2022, TB 029, available
at: <a href="https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/">https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/https://www.euroncap.com/en/for-engineers/protocols/adult-occupant-protection/</a>.
---------------------------------------------------------------------------

The S-Track is similar to the IR-TRACC in that it is in-dummy
instrumentation that attaches to the same points in the dummy as the
IR-TRACC. Both measure linear displacement, and when coupled with the
gimballed potentiometers, their signals can be post-processed to
calculate three-dimensional motion. It differs in that the S-Track uses
a mechanical scissor mechanism coupled to a linear potentiometer to
measure linear motion along its axis, while the IR-TRACC uses a
measurement of light transmittance, which requires a linearization
calculation to estimate linear motion.
NHTSA has conducted a range of testing to evaluate the performance
and equivalence of the S-Track. The testing, which included a partial
qualification test series and sled tests, is briefly summarized
below.\92\ A more detailed discussion of this material is available in
a previously published paper (except, as noted below, the second set of
sled tests, for which a report is forthcoming).\93\
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\92\ This evaluation of alternate thorax and abdomen
instrumentation only considered replacement of the displacement
transducer component of the 3D IR-TRACC measurement system. Though
it was not available at the time of purchase, a double gimbal kit to
allow 3D measurement is now available from the S-Track manufacturer.
ATD-Labtech GmbH (2017). 3D Adaption THOR-50th upper Thorax left
20_303. Available at: <a href="https://www.atd-labtech.com/files/atd/uploads/produkte/s-track/produkte/4%20TH-3D-Adapter-Upper-Thorax-left/data_sheet-3D-Adaption_Thor-50th_upper_Thorax_left%20Rev%2001.PDF">https://www.atd-labtech.com/files/atd/uploads/produkte/s-track/produkte/4%20TH-3D-Adapter-Upper-Thorax-left/data_sheet-3D-Adaption_Thor-50th_upper_Thorax_left%20Rev%2001.PDF</a>.
To evaluate whether the S-Track 3D adaption kit would result in
equivalent measurement capabilities as the 3D IR-TRACC measurement
system, the testing described here would be repeated, starting with
the 3D static measurement assessment.
\93\ Hagedorn, A., Murach, M., Millis, W., McFadden, J., Parent,
D., (2019). Comparison of the THOR-50M IR-TRACC Measurement Device
to an Alternative S-Track Measurement Device. Proceedings of the
Forty-Seventh International Workshop on Human Subjects for
Biomechanical Research. Available at: <a href="https://www-nrd.nhtsa.dot.gov/pdf/bio/proceedings/2019/Hagdeorn_S-Track_Biomechanics%20Workshop%202019_FINAL.pdf">https://www-nrd.nhtsa.dot.gov/pdf/bio/proceedings/2019/Hagdeorn_S-Track_Biomechanics%20Workshop%202019_FINAL.pdf</a>.
---------------------------------------------------------------------------

<bullet> The range and linearity of the S-Track and IR-TRACC
sensors are comparable. The range of measurement of the S-Track is
consistent with or larger than the range of measurement of the IR-
TRACC, and all sensors were within the manufacturer's specification for
the maximum allowable linear error as a percentage of full scale. This
specification (0.5%) is tighter compared to the corresponding IR-TRACC
specification (2%), though only one of the IR-TRACCs (right abdomen)
showed a linearity error greater than 0.5%.
<bullet> Calibration and 3D static measurement assessments
demonstrated similar or better accuracy compared to the IR-TRACC in the
double-gimbal configuration for the upper left thorax, lower left
thorax, and left abdomen. In the upper and lower thorax configurations,
the S-Track showed less error than the IR-TRACC, and in the abdomen
configuration, showed errors similar to the IR-TRACC.
<bullet> The form, fit, and function is comparable to the IR-TRACC.
A full set of six S-Tracks was installed in a THOR-50M ATD. It did not
present any connectivity or interference issues and appeared to be a
plug-and-play replacement to the IR-TRACCs. One possible durability
issue was identified

[[Page 61909]]

(damage to the cable at the base of the S-Track). This issue is
mitigated if cable routing documentation is followed or the S-Track-
specific double-gimbal assembly is used.
<bullet> The S-Track performed equivalently in qualification tests.
NHTSA carried out the qualification tests for the body regions expected
to be sensitive to a difference in thorax and abdomen instrumentation
(upper thorax, lower thorax, and abdomen) on a THOR-50M in two
different configurations: a baseline configuration with IR-TRACCs in
all locations, and an alternate configuration with S-Tracks in all
locations. Both configurations met the qualification targets for all of
the test modes specified for those body regions, which demonstrates
that the difference in measured deflections between the S-Track and IR-
TRACC were well within expected test-to-test variation. In addition,
the deflection time-history was qualitatively similar to the IR-TRACC.
<bullet> The S-Track performed equivalently to the IR-TRACC in most
respects in a series of sled tests. NHTSA conducted sled tests in
several conditions with the THOR-50M in two configurations: one with
the IR-TRACC in all locations, and one with the S-Track in all
locations:
[cir] The first series used a reinforced buck representative of the
front half of a mid-sized passenger vehicle (including seat belt,
frontal air bag, and side curtain air bag) and simulated a near-side
frontal oblique (20 degrees) crash. The crash pulse was based on a
frontal oblique crash test of the same vehicle. The S-Track proved to
be durable and did not demonstrate the same noise artifacts as the IR-
TRACC. The S-Tracks in the thorax showed similar measurements as the
IR-TRACCs, particularly in the upper right thorax, the closest
measurement location to the shoulder belt. There were some potential
differences between the abdomen measurements, but abdominal deflection
is not currently included as an injury criterion in FMVSS No. 208 and
is not currently included in the rating calculation for frontal
NCAP.\94\
---------------------------------------------------------------------------

\94\ Additional evaluation would be desirable in cases where
abdominal deflection is a critical measurement, such as a rear seat
environment where submarining may be more likely to occur.
---------------------------------------------------------------------------

[cir] The second series of sled tests were conducted in the Gold
Standard 1 (40 km/h, 12g peak pulse, standard lap and shoulder belt)
and Gold Standard 2 (30km/h, 9g peak pulse, 3kN load limited shoulder
belt) test conditions, which were used both in biofidelity assessment
and in the development of thoracic injury criteria.\95\ The goal of
this testing was to determine if any differences occurred between the
IR-TRACC and S-Track measurement devices, and if so, whether the
magnitude of these differences would affect the biofidelity and injury
criteria development analyses. NHTSA is preparing a report on this
second series of sled tests, which will be placed in the research
docket when it is complete.
---------------------------------------------------------------------------

\95\ The Gold Standard 1 test uses a flat rigid seat, standard
lap and shoulder belts, knees restrained, and right front passenger
restraint geometry. The Gold Standard 2 test uses a flat rigid seat,
a force-limited shoulder belt and standard lap belt, knees
restrained, and right front passenger restraint geometry.
---------------------------------------------------------------------------

Based on this testing and analysis, NHTSA believes that the S-Track
is equivalent to the IR-TRACC (with the potential exception of the
abdomen deflection in a sled test environment).
Proposal
NHTSA proposes to specify both the IR-TRACC and the S-track as
permissible instrumentation for the THOR-50M. A THOR-50M configured
with all IR-TRACCs or all S-tracks would conform to Part 572 and NHTSA
could perform compliance testing with either device installed in the
THOR-50M. The dummy has not been tested in a mixed configuration, with
both devices installed (e.g., IR-TRACCS in the chest and S-Tracks the
abdomen, or with one IR-TRACC and three S-Tracks in the chest). The
overall effects of such configurations are unknown. NHTSA seeks comment
on whether the final specifications should allow such configurations.
The IR-TRACC is specified in the 2023 drawing package (in SA572-S117
and SA572-S121). NHTSA has not yet published engineering drawings and
parts packages to specify how the S-Track is installed in the dummy,
but intends to integrate such documentation into the associated
technical data package components upon finalization of this proposal.
NHTSA seeks comment on this proposal.

F. Shoulder

The THOR-50M shoulder was developed to allow a human-like range of
motion and includes a clavicle linkage intended to better represent the
human shoulder interaction with shoulder belt restraints.\96\ Clavicle
load cells that can be installed in the proximal and distal ends of the
clavicles are commercially available, but these load cells are not
currently defined in the drawing package and NHTSA has not evaluated
them.
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\96\ T[ouml]rnvall, F.V., Holmqvist, K., Davidsson, J.,
Svensson, M.Y., H[aring]land, Y., [Ouml]hrn, H., ``A New THOR
Shoulder Design: A Comparison with Volunteers, the Hybrid III, and
THOR NT,'' Traffic Injury Prevention, 8:2, 205-215, 2007.
---------------------------------------------------------------------------

Below we discuss shoulder components for which NHTSA is proposing
alternative permissible specifications (the alternate shoulder) or for
which design modifications have been developed by external THOR-50M
users but which NHTSA has tentatively decided not to incorporate in the
drawing package (shoulder slip and coracoid process).
1. Alternate Shoulder Specification
Portions of the shoulder assembly specified in the 2018 drawing
package (referred to as the SD-3 shoulder) are covered by a patent
issued to Humanetics. However, for the reasons discussed in more detail
in Section VIII, NHTSA has generally avoided specifying in Part 572
patented components or copyrighted designs without either securing
agreement from the rights-holder for the free use of the item or to
license it on reasonable terms or developing an alternative
unencumbered by any rights claims. NHTSA has therefore designed, built,
and tested an alternative design for a part of the shoulder assembly
referred to as the shoulder pivot assembly that is not subject to any
intellectual property claims. Accordingly, the proposed drawing package
(the 2023 drawing package) includes specifications for the SD-3
shoulder pivot assembly as well as the alternate shoulder pivot
assembly, so that either may be used. We explain this in more detail
below.
SD-3 Shoulder
The SD-3 shoulder is notably different from the shoulder specified
for the THOR-NT. The THOR-NT design includes a clavicle linkage
attached by ball joints at the sternum and acromion, a linkage between
the acromion and the scapula to which the upper arm attaches, and a
linkage representing the scapula that attaches to the acromion linkage
and the spine with unconstrained revolute joints. While there were some
benefits of the THOR-NT design compared to existing ATDs at the time,
the range of motion of the THOR-NT shoulder was found to be lacking
compared to the human shoulder.\97\
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\97\ Shaw, G., Parent, D., Purtsezov, S., Lessley, D., Crandall,
J., Tornvall, F., ``Torso Deformation in Frontal Sled Tests:
Comparison Between THOR-NT, THOR-NT with the Chalmers SD-1 Shoulder,
and PMHS,'' Proceedings of the International IRCOBI Conference,
2010.
---------------------------------------------------------------------------

An improved shoulder design was independently initiated by the
Chalmers University of Technology (Chalmers), in

[[Page 61910]]

a project sponsored by Volvo and Autoliv, that sought to improve the
prediction of occupant response in offset and oblique frontal crashes.
Several prototype shoulder assemblies were constructed and evaluated,
the most promising being labeled the Shoulder Design 1 (SD-1).\98\ The
SD-1 shoulder design includes a clavicle linkage with human-like
geometry, connected by cardan joints to the sternum and acromion; a
linkage representing the scapula that includes attachment to the upper
arm; and a two-part linkage connecting the scapula to the spine which
allows both upward and anterior motion of the shoulder assembly. The
anterior rotation of the scapula linkage about a vertical shaft is
governed by a coil spring within an assembly mounted to the spine box.
Several rotation stops are installed throughout the assembly to prevent
metal-to-metal contact at the extents of the range-of-motion.
---------------------------------------------------------------------------

\98\ T[ouml]rnvall et al. (2007), 205-215.
---------------------------------------------------------------------------

After evaluation of the SD-1 in dynamic sled testing in comparison
to the standard THOR-NT shoulder and to PMHS,\99\ several improvements
were proposed, including durability improvements to the humerus joint,
decreasing the range of motion in the anterior and superior directions,
and increasing the range of motion in the posterior and medial
directions. The improved design, labelled as the SD-2 shoulder, was
fabricated by GESAC to Chalmers' specifications, installed on a THOR-
50M ATD, and evaluated in sled tests in the Gold Standard 1 and Gold
Standard 2 conditions at the University of Virginia.\100\ Several
additional durability and usability concerns were raised upon post-test
inspection, including deformation of the joint between the clavicle and
the acromion and hard contact to the humerus joint.
---------------------------------------------------------------------------

\99\ Shaw et al (2010).
\100\ Crandall, J. (2013). ATD Thoracic Response: Effect of
Shoulder Configuration on Thoracic Deflection. NHTSA Biomechanics
Database, Report b11017R001, available at: <a href="https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11017&index=1&database=B&type=R">https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11017&index=1&database=B&type=R</a>.
---------------------------------------------------------------------------

Subsequently, an updated version of the SD-2 shoulder, known as the
SD-3, was designed and fabricated as part of the European Union's
Thoracic Injury Assessment for Improved Vehicle Safety (THORAX)
project.\101\ Changes introduced in the SD-3 design included redesigned
sterno-clavicular joint anthropometry, an updated shoulder cover, and
improvements intended to address the durability and usability concerns
raised by the University of Virginia testing. These latter improvements
consisted of replacing the clavicle U-joint with a spherical joint;
replacing the humerus joint with a metric version of the HIII-50M upper
arm joint; and introducing a series of washers and bushings to the
bottom of the vertical shaft to enable the resistance of the assembly
to be adjusted to allow a more reproducible initial position.
---------------------------------------------------------------------------

\101\ Lemmen, P., Been, B., Carroll, J., Hynd, D., Davidsson,
J., Song, E., and Lecuyer, E. (2012). Development of an advanced
frontal dummy thorax demonstrator. Proceedings of the 2012 IRCOBI
Conference, Paper No. IRC-12-87, September 2012.
---------------------------------------------------------------------------

The SD-3 shoulder was installed on a THOR-50M ATD and sled testing
was again carried out at the University of Virginia in the Gold
Standard 1 and Gold Standard 2 conditions, as well as a variation of
Gold Standard 1 with a force-limited belt.\102\ The SD-3 shoulder
assembly was inspected in detail throughout this testing, and no
evidence of damage was identified. The chest deflection and torso
motion was similar to the SD-1 and SD-2 shoulders, while durability was
improved. NHTSA also conducted an evaluation of blunt thoracic impact
response of several configurations of THOR-50M ATDs and found the
iteration with the SD-3 shoulder assembly installed to have the highest
qualitative and quantitative biofidelity.\103\ Given these findings,
NHTSA modified the drawing package to include the SD-3 shoulder. The
first iteration of the drawing package to include the SD-3 shoulder was
published as the September 2014 version.\104\
---------------------------------------------------------------------------

\102\ Crandall, J. (2013). ATD Thoracic Response: SD3 Shoulder
Evaluation. NHTSA Biomechanics Database, Report b11470R001,
available at: <a href="https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11470&index=1&database=B&type=R">https://www-nrd.nhtsa.dot.gov/database/MEDIA/GetMedia.aspx?tstno=11470&index=1&database=B&type=R</a>.
\103\ Parent, D., Craig, M., Ridella, S., McFadden, J.,
``Thoracic Biofidelity Assessment of the THOR Mod Kit ATD,'' The
23rd Enhanced Safety of Vehicles Conference, Paper No. 13-0327,
2013.
\104\ National Highway Traffic Safety Administration (2014).
THOR 50th Percentile Male Drawing Package, September 2014. available
at: <a href="https://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR%20Advanced%20Crash%20Test%20Dummy/thoradv/THOR-M_PDF_2014-09-29.pdf">https://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR%20Advanced%20Crash%20Test%20Dummy/thoradv/THOR-M_PDF_2014-09-29.pdf</a>.
---------------------------------------------------------------------------

After the publication of the September 2014 drawing package,
Humanetics filed an application for a patent describing a shoulder
assembly as well as an upper arm with an integrated load cell.\105\
Similar to the SD-3 shoulder, the design patent describes a shoulder
pivot assembly which includes, among other things, a coil spring and an
adjustable resistance element. After discussions between NHTSA and
Humanetics, a disclaimer stating that portions of the THOR-50M drawings
were covered by a Humanetics patent was added first to the NHTSA
website where the drawings were available for download, and later to
the drawings for the shoulder and upper arm assemblies in the drawing
package itself.
---------------------------------------------------------------------------

\105\ Been, B., & Burleigh, M. (2017). U.S. Patent No.
9,799,234. Washington, DC: U.S. Patent and Trademark Office.
---------------------------------------------------------------------------

NHTSA has generally avoided specifying such parts, consistent with
the legislative history of the Safety Act. (See Section VIII,
Intellectual Property.) For this reason, as explained below we are also
proposing, in addition to the SD-3 shoulder, an alternative shoulder
pivot assembly design.
Alternate Shoulder Pivot Assembly Design
To address the potential issues with specifying only a proprietary
shoulder design, NHTSA has designed, built, and tested an alternate
shoulder pivot assembly that is not subject to any intellectual
property claims. The alternate shoulder pivot assembly does not include
any components to adjust the resistance of the assembly, and does not
use a coil, clock, or watch-spring mechanism. Instead, the alternate
shoulder pivot assembly design uses a molded rubber cylinder acting as
a torsion bar. The top of the cylinder is attached to the shoulder
support assembly and the bottom is attached to the spring housing, so
rotation of the shoulder about the local Z-axis of the ATD results in
torsion of the rubber cylinder. In order to adjust the resistance of
the assembly, the springs must be removed and replaced.
NHTSA has evaluated the alternate shoulder in a variety of tests
and tentatively concludes that its performance is similar to the SD-3
shoulder based on testing carried out to date. This testing, which
included a partial qualification test series and sled tests, is briefly
summarized below. A more detailed discussion of this material is
available in a testing report that NHTSA is preparing, and which will
be placed in the research docket when it is completed. NHTSA is also
preparing another report that describes additional sled testing that
was conducted; this report will be placed in the research docket when
it is complete.
First, the alternate shoulder was installed in a THOR-50M without
any issues regarding the form, fit, or function. Second, in a quasi-
static rotation test, the alternate shoulder showed a similar moment-
rotation loading slope to the SD-3 shoulder in both the forward and
rearward rotation directions. Third, the SD-3 and alternate shoulder
showed nearly identical longitudinal motion in all three loading
directions in a quasi-static biofidelity evaluation comparing each

[[Page 61911]]

shoulder's range of motion to that of human volunteers; the responses
of both were generally similar to the human volunteer response
corridors. Fourth, the qualification tests most likely to be affected
by shoulder response (upper thorax and chest) were carried out; the
THOR-50M with the alternate shoulder met all qualification
specifications for the upper thorax, and the force-deflection
characteristic of the chest was nearly identical to that of a THOR-50M
with the SD-3 shoulder. Finally, sled tests conducted in both a full
frontal and a far-side oblique condition did not reveal any durability
or usability issues, and the response of the THOR-50M with the
alternate shoulder was within the test-to-test variation of the THOR-
50M with the SD-3 shoulder.
NHTSA is therefore proposing the alternative shoulder as an
acceptable optional subassembly. The shoulder assemblies are specified
on drawings 472-3810 (left) and 472-3840 (right). Each shoulder
assembly drawing specifies that either the SD-3 shoulder pivot assembly
or the alternate shoulder pivot assembly may be used. The proposed
specifications for the SD-3 shoulder pivot assembly are provided in
drawings 472-3811 and 472-3841, and the proposed specifications for the
alternate shoulder pivot assembly are provided in drawings 472-6810-1
and 472-6810-2. The drawing package currently indicates that the
selection of which shoulder pivot assembly to use is made separately
for the left and right shoulder assemblies, so that the dummy could be
fitted with the SD-3 shoulder pivot assembly on one side, and the
alternate shoulder pivot assembly on the other side. The dummy has not
been tested in such a mixed configuration, and the overall effects of
such configurations are unknown. NHTSA seeks comment on whether the
final specifications should allow such mixed configurations.
NHTSA seeks comment on whether the final drawing package should
include the SD3 shoulder, the alternate shoulder, or both. NHTSA also
seeks comment from THOR-50M users who have evaluated the proposed
alternate shoulder design, or other alternate shoulder designs, and
have data related to equivalence with respect to durability,
repeatability and reproducibility, and response in qualification,
biofidelity, injury and vehicle crash test conditions.
2. Shoulder Slip
NHTSA is aware that some researchers and regulatory authorities
have identified what they view as a possible design flaw in the
shoulder--that the shoulder belt may slip towards the neck in a crash--
and have developed potential modifications to the shoulder design to
prevent this from happening.
This concern was first raised in a 2018 conference paper describing
research conducted by Transport Canada. Transport Canada conducted a
series of vehicle crash tests with the THOR-50M in the driver seat in
two conditions: 40% offset and full frontal rigid barrier.\106\ It was
reported that the upper portion of the shoulder belt could translate
towards the neck and become entrapped in the gap between the neck and
the shoulder. This occurred in 33 of the 45 offset tests and in 2 of
the 13 full frontal rigid barrier tests. Compared to tests without
shoulder belt slip, tests with shoulder belt slip showed higher
measurements for lower neck shear (X-axis and Y-axis force), higher
chest deflections in the upper left and lower right quadrants, and
lower clavicle axial forces.
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\106\ Tylko, S., Tang, K., Giguere, F., Bussieres, A. (2018).
Effects of Shoulder-belt Slip on the Kinetics and Kinematics of
THOR. Proceedings of the 2018 IRCOBI Conference.
---------------------------------------------------------------------------

Following that research, a 2019 Humanetics study identified and
evaluated three prototype alternative modifications to the shoulder
specified in the 2018 drawing package to prevent the shoulder belt from
entering the gap between the neck and the shoulder.\107\ The study
concluded that all three prototype modifications prevented belt
entrapment and identified the preferred design alternative (referred to
as a profiled split design). While the shoulder specified by NHTSA uses
the same material for the entire shoulder pad, the profiled split
design replaces the material closest to the neck with a higher-
stiffness plastic material. This is intended to prevent the collar (the
portion of the shoulder pad closest to the neck) from deforming and
allowing the shoulder belt to slip towards the neck.
---------------------------------------------------------------------------

\107\ Wang, Z.J., Fu, S., McInnis, J., Arthur, J. (2019).
Evaluation of Novel Designs to Address the Shoulder-belt Entrapment
for THOR-50M ATD. Proceedings of the 2019 IRCOBI Conference.
---------------------------------------------------------------------------

In addition, in recent discussions with NHTSA, Euro NCAP has noted
that several instances of shoulder belt slippage were observed in Euro
NCAP testing as well as research tests with the mobile progressive
deformable barrier. Euro NCAP reported that it was evaluating two
potential shoulder design modifications, and expected these to be
presented for approval in 2023.
While NHTSA has witnessed the shoulder belt moving towards the neck
in vehicle crash tests, this phenomenon does not appear to influence
dummy measurements related to injury criteria. NHTSA seeks comment on
the desirability of and specifications for a modification to prevent
belt slippage, including data on testing with the proposed shoulder
design showing that it is leading to belt slippage that has a
meaningful effect on test results. NHTSA also requests comment from
THOR-50M users who have evaluated the split shoulder pad (or any
available alternatives) and have data to support equivalence of
durability, repeatability and reproducibility, and response in
qualification, biofidelity, injury criteria, and vehicle crash test
conditions.

G. Hands

The THOR-50M specified in the 2023 drawing package includes the
same hand design as the HIII-50M. The drawing defining the hand
assembly of the THOR-50M \108\ includes material formulation (Solid
Vinyl, Formulation Portland Plastics, PM-7003) along with two two-
dimensional images and one three-dimensional image of the hand.
Additionally, the three-dimensional geometry of the hand assembly is
included in the computer-aided design (CAD) files available through the
NHTSA website in both Autodesk Inventor and generic STEP formats.
However, the vinyl call-out does not sufficiently specify the hardness
or the stiffness of the material formulation and may be insufficient to
define the part. NHTSA therefore seeks comment on whether there is a
need for a material test (e.g., hardness measurement or a quasi-static
compression test of a coupon of the material) or performance test
(e.g., quasi-static or dynamic impact to the as-fabricated hand) to
further define the hand assembly of the THOR-50M, and if so, what the
test might be.
---------------------------------------------------------------------------

\108\ Drawing 472-6900-1/2.
---------------------------------------------------------------------------

H. Spine

The spine of the THOR-50M ATD is primarily constructed of steel.
There are two flexible elements (one in the thoracic spine and one in
the lumbar spine) that are intended to allow human-like spinal
kinematics in both frontal and oblique loading conditions.\109\ Between
the two flexible elements is a posture adjustment joint known as the
lumbar spine pitch change mechanism, which allows the posture of the
THOR-50M to be adjusted into various seating configurations in three-

[[Page 61912]]

degree increments, including, but not limited to, four designated
positions (erect, neutral, slouched, and super slouched).\110\ The
spine is instrumented with a five-axis thoracic spine load cell mounted
below the lumbar spine pitch change mechanism and above the lumbar
spine flex joint (a flexible joint that allows the dummy to go into
flexion/extension in the lumbar region). Triaxial accelerometers can be
installed in the nominal locations of the first, sixth, and twelfth
thoracic vertebra.
---------------------------------------------------------------------------

\109\ Haffner, M., Rangarajan, N., Artis, M., Beach, D.,
Eppinger, R., Shams, T. (2001). Foundations and Elements of the
NHTSA THOR Alpha ATD Design. The 17th International Technical
Conference for the Enhanced Safety of Vehicles, Paper No. 458.
\110\ See Fig. 5-32 in the PADI.
---------------------------------------------------------------------------

The proposed spine design differs from the THOR-50M used by Euro
NCAP. Whereas the 2023 drawing package specifies a lumbar spine pitch
change mechanism, TB026 specifies a four-position lumbar spine box or
an ``alternative spine box'' if ``data has been provided to show
equivalence between the NHTSA spine assembly and modified spine
assembly.'' \111\ Humanetics holds a patent on the four-position spine.
The four-position lumbar spine is not specified further, but it does
differ from the spine specified by the NHTSA drawings. The spine pitch
change mechanism specified in the 2023 drawing package allows the spine
to be set at a multitude of flexion or extension settings, not just
four. NHTSA understands that the Euro NCAP design is intended to
accommodate the in-dummy installation of some DAS brands by providing a
mounting surface for data loggers. THOR-50M units built for Euro NCAP
are configured with in-dummy DAS systems have the four-position spine.
---------------------------------------------------------------------------

\111\ Sec. 1.4.3.
---------------------------------------------------------------------------

NHTSA has tentatively decided not to specify a lumbar spine pitch
change mechanism limited to four positions for a few reasons. First,
NHTSA has not inspected, nor has it performed any testing with, the
four-position spine. Second, NHTSA generally avoids specifying patented
components in Part 572 (see Section VIII, Intellectual Property).
Third, the proposed spine specifications provide more adjustability
than the four-position spine so the dummy may be used in a wider range
of applications. NHTSA seeks comment on user experience with the four-
position spine, including any data on equivalence with the THOR-50M as
specified in the 2023 drawing package or biofidelity.
It is also NHTSA's understanding that members of Working Group 5
have observed variations in the ATD responses in the upper thorax
qualification tests that have led to difficulties in meeting the Euro
NCAP qualification specifications. Some manufacturers have suggested
that this variation in response is due to variation in the spine flex
joint (specifically, the vertical displacement (Z-axis) of the ribs is
too high). One potential cause that has been identified (by Porsche in
November 2019) is that that the hardness of the material comprising the
spine flex joint was lower than the specification called for.
NHTSA's qualification testing did not reveal any issues with
meeting the upper thorax qualification specifications (See Section
V.D). In any case, in light of the potential concerns raised within
Working Group 5 of possible excessive variation in the performance of
the spine flex joint, potentially traceable to out-of-specification
materials, NHTSA conducted a limited modeling exercise using the THOR-
50M Finite Element (FE) model to investigate this. This analysis
suggested that while variation in the lumbar and thoracic spine flex
joints does influence the thoracic response in both qualification and
sled test conditions, this variation is smaller than the expected test-
to-test and ATD-to-ATD variation; specifically, a decrease in stiffness
of the spine flex joints can influence the upper thorax qualification
response, but by a much smaller magnitude than the width of the
qualification specifications and test-to-test and ATD-to-ATD
variations. For more information on this issue and NHTSA's FE
modelling, please see Appendix B.
Nonetheless, a research effort is currently underway to assess the
influence of the lumbar and thoracic spine flex joints in physical
qualification tests (which would provide additional validation data to
the computational analysis) and develop isolated dynamic tests of the
lumbar and thoracic spine flex joints. Based on these results, NHTSA
could potentially consider adding such a test(s) in the drawing
package, qualification procedures, or laboratory test procedures. NHTSA
requests comment from THOR-50M ATD users who have data to demonstrate
variation in THOR-50M response that is believed to result from spine
flex joint variation, specifically when the parts evaluated met the
specifications of the THOR-50M drawing package. Additionally, NHTSA
requests comment on the need for a thoracic spine and/or lumbar spine
flex joint specification beyond the geometry and material properties
defined in the drawing package.

I. Abdomen

The abdomen of the THOR-50M consists of two components, the upper
abdomen and the lower abdomen. The lower abdomen is the region between
the lower thoracic rib cage and the pelvis. The upper abdomen is the
region on the dummy that represents the lower thoracic cavity, which
fills the volume that exists between the lowest three ribs, above the
lower abdomen and in front of the spine. The upper and lower abdomen
components of THOR-50M are represented by structural fabric bags
containing foam inserts which define the compression stiffness. Both
abdomen inserts are anchored posteriorly to the spine, while the upper
abdomen insert is additionally anchored to the lower rib cage. When the
lumbar spine pitch change joint is set to the ``slouched'' position,
the abdomen inserts are in contact with one another; when in the
``erect'' and ``neutral'' positions, the gap between the abdominal
inserts is filled with the lower abdomen neutral/erect position foam.
This gap is also spanned by two steel stiffeners on each side that are
installed into the torso jacket. The bottom surface of the lower
abdomen insert is coincident with the pelvis.

J. Pelvis

The THOR-50M pelvis is designed to represent human pelvis bone
structure to better represent lap belt interaction,112 113
and the pelvis flesh is designed to represent uncompressed geometry to
allow human-like interaction of the pelvis flesh with the vehicle
seat.\114\ The pelvis assembly is constructed of a steel and aluminum
structure representing bone surrounded by a molded foam-filled vinyl
covering representing flesh. The flesh is not physically connected to
the pelvis bone but is held in place due to the tight fit of
protrusions of the pelvis bone into recesses in the pelvis flesh, as
well as circular bosses in the pelvis flesh into recesses in the pelvis
bone. The pelvis flesh includes a portion of the upper thigh flesh, the
interior surface of which includes gaps around the femur bone to allow
articulation of the leg about the hip joint.
---------------------------------------------------------------------------

\112\ Reynolds, H., Snow, C., Young, J., ``Spatial Geometry of
the Human Pelvis,'' U.S. Department of Transportation, Technical
Report No. FAA-AM-82-9, 1982.
\113\ Haffner, M., Rangarajan, N., Artis, M., Beach, D.,
Eppinger, R., Shams, T., ``Foundations and Elements of the NHTSA
THOR Alpha ATD Design,'' The 17th International Technical Conference
for the Enhanced Safety of Vehicles, Paper No. 458, 2001.
\114\ Shams, T., Rangarajan, N., McDonald, J., Wang, Y.,
Platten, G., Spade, C., Pope, P., Haffner, M., ``Development of THOR
NT: Enhancement of THOR Alpha--the NHTSA Advanced Frontal Dummy,''
The 19th International Technical Conference for the Enhanced Safety
of Vehicles, Paper No. 05-0455, 2005.
---------------------------------------------------------------------------

The THOR-50M pelvis flesh is a molded component, with a vinyl outer

[[Page 61913]]

layer filled with expandable polyurethane foam. The two-dimensional
drawing includes top, side, front, and isometric views of the molded
pelvis flesh, while its three-dimensional geometry is included in the
CAD files available through the NHTSA website in both Autodesk Inventor
and generic STEP formats. The drawing package specifies part weight and
foam density \115\ but not a material response or performance
requirement for the pelvis flesh.
---------------------------------------------------------------------------

\115\ Drawing 472-4100.
---------------------------------------------------------------------------

NHTSA is considering adding a performance specification for the
pelvis flesh similar to that defined in the HIII-50M PADI. Such a
performance specification would dictate the amount of allowable
compression of the pelvis flesh under a defined load. A similar test
was conducted on the pelvis flesh during the THOR Alpha design
development.\116\ One such possible requirement would be the
compression at a force of 500 N. Alternatively, Porsche has suggested a
dynamic impact test using an impactor similar to that used in the upper
thorax qualification test to impact the bottom of the pelvis flesh at a
velocity of 2 m/s. NHTSA seeks comment on the need and specifications
for a pelvis compression test, including whether it should be a
qualification requirement, a drawing specification, or otherwise.
---------------------------------------------------------------------------

\116\ White Jr, R.P., Rangarajan, N., Haffner, M., ``Development
of the THOR Advanced Frontal Crash Test Dummy'', 34th Annual SAFE
Symposium, Conference paper, 1996.
---------------------------------------------------------------------------

The pelvis is instrumented with bi-lateral triaxial load cells
attached to the acetabulum (in order to measure the reaction force
between the femur and the pelvis) and a triaxial accelerometer array at
its center of gravity. The pelvis is also instrumented with bi-lateral
anterior-superior iliac spine (ASIS) load cells that measure contact
force in a nominally longitudinal axis and moment about a nominally
lateral axis. The ASIS load cell is primarily used to measure the force
transferred to the pelvis through the lap belt, in which case the
moments can be used to determine the vertical level or center of
pressure of the lap belt force.

K. Upper Leg

The upper leg assembly is constructed of steel and aluminum and
includes a rubber compressive element at the middle of the femur shaft.
This compressive element consists of a steel plunger that can translate
axially along the femur shaft through a guide system. When the femur is
loaded in axial compression (e.g., pushing the knee towards the pelvis
parallel to the femur), the motion of the plunger is resisted by a
rubber element, which allows a human-like compression response.\117\ At
the proximal end, the femur is connected to the pelvis through a ball
joint in a socket attached to the acetabulum load cell. At the distal
end, there is a six-axis load cell attaching the femur to the knee
assembly.
---------------------------------------------------------------------------

\117\ Ridella, S., Parent, D., ``Modifications to Improve the
Durability, Usability, and Biofidelity of the THOR-NT Dummy,'' The
22nd International Technical Conference for the Enhanced Safety of
Vehicles, Paper No. 11-0312, 2011. See Figure 17.
---------------------------------------------------------------------------

L. Knee

The THOR-50M knee is similar in construction to that of the HIII-
50M, with a few differences. The primary structure of the knee cap is
fabricated from aluminum, attached proximally to the femur load cell.
Inside of the kneecap assembly, a slider mechanism is installed to
allow translational motion of the tibia with respect to the knee. The
knee slider includes a stop assembly to prevent metal-to-metal contact
and to define the force-deflection characteristic of the tibia
translation. Attached to the slider is a string potentiometer to
measure the magnitude of tibia translation relative to the knee. The
sides of the kneecap are enclosed by urethane covers to protect the
slider mechanism, and the knee assembly is wrapped in a foam-filled
vinyl cover representing knee flesh.
The design of the knee slider modifies the HIII-50M design by
changing the geometry and material properties of the molded slider
assemblies (472-5320 and 472-5330) and stop assemblies (472-5358).\118\
This change was made because at levels of knee displacement below the
10.2-millimeter (mm) biofidelity response requirement, the HIII-50M has
been found to be stiffer than PMHS response corridors. Thus, during the
THOR-50M Mod Kit project, biomechanical response requirements were
specified with an additional measurement point at 5 mm of knee
displacement with a force between 100 and 500 N. The Mod Kit also
relegated the measurement point at 10.2 mm of deflection to a secondary
requirement, as it was shown to be at the high end of the underlying
PMHS corridors. While the 5 mm and 17.8 mm response requirements were
met by the revised THOR-50M knee slider,\119\ the force-deflection
response was below the human response corridor between 8 mm and 15 mm
of deflection, but above the corridor after 18 mm of deflection.\120\
As such, when the biofidelity was evaluated using BioRank, the external
biofidelity score of 2.282 indicated that the THOR-50M response was
more than two standard deviations from the PMHS mean response. This
BioRank score was lower than the corresponding HIII-50M score (1.070).
This should be taken into consideration when using the THOR-50M to
evaluate the risk of ligamentous knee injury.
---------------------------------------------------------------------------

\118\ Id. at Figure 16.
\119\ Id.
\120\ See Biofidelity Report, p. 254 (Fig. 45).
---------------------------------------------------------------------------

M. Lower Leg

The mechanical design of the THOR-50M lower extremity includes a
compressive rubber section in the tibia shaft, similar to the compliant
femur section, which provides more biofidelic force transmission from
the heel to the knee. The spring damper Achilles tendon system aids in
producing biofidelic ankle motion and torque characteristics. The ankle
design allows rotation about three axes, representing inversion/
eversion, dorsi/plantar-flexion, and axial rotation, and includes
molded rubber elements to define the moment/rotation response and limit
metal-to-metal contact at the extents of the range of motion. Different
from existing ATDs, the THOR-50M includes a molded shoe design which
integrates the foot and shoe into a single part. This feature, added in
the 2016 update to the THOR-50M drawing package,\121\ is intended to
reduce potential variability in the response of commercially available
shoes.
---------------------------------------------------------------------------

\121\ National Highway Traffic Safety Administration (2016).
Parts List and Drawings THOR-50M Advanced Frontal Crash Test Dummy
THOR-50M Male August 2016. Docket ID NHTSA-2015-0119-0376.
---------------------------------------------------------------------------

Euro NCAP TB026 deviates from the proposed drawing package in that
it specifies the HIII-50M lower legs, including the military
specification \122\ shoes, knee slider sensor, and roller ball-bearing
knees. We believe the THOR-50M specifications are preferable, for the
reasons given above (e.g., biofidelity).
---------------------------------------------------------------------------

\122\ Specification is not stated in Euro NCAP TB026, but
believed to be MIL-S-13192P as specified in 49 CFR 571.208 S8.1.8.2.
---------------------------------------------------------------------------

Each lower leg can be instrumented with five-channel load cells in
the upper and lower tibia, a uniaxial load cell to measure the Achilles
cable force, and three rotary potentiometers to measure the rotation of
the individual ankle joints. Two uniaxial accelerometers can be mounted
to the tibia and a tri-pack accelerometer assembly can be mounted to
each foot plate.

N. Data Acquisition System

Testing with THOR-50M requires (as does testing with any dummy) a
data

[[Page 61914]]

acquisition system (DAS). The data acquisition system performs signal
conditioning, triggering, and data collection to store measurements
from instrumentation installed in the dummy during a test into
nonvolatile memory. As it relates to ATDs, there are effectively two
types of DAS: external and internal (or in-dummy). As we explain below,
while the 2018 drawing package does not specify a DAS (because it
assumes the use of an external DAS), NHTSA is proposing to specify an
optional in-dummy DAS.\123\
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\123\ We note that the 2023 drawing package itself does not
contain specifications for an in-dummy DAS. Instead, the proposed
in-dummy DAS specifications are set out in an addendum that is being
docketed along with the 2023 drawing package.
---------------------------------------------------------------------------

An external DAS is, as the name indicates, external to the dummy.
The instrumentation in the dummy is connected to the external DAS via
wires, sometimes referred to as an umbilical cable. The 2018 drawing
package does not explicitly specify a DAS or related equipment, but the
drawings assume an external DAS: they assume that the instrumentation
wires are long enough to be bundled into an umbilical cable and
connected to a DAS located in the lab or mounted to the vehicle in
which the ATD is seated.
An internal DAS is installed within the dummy itself. An internal
DAS has some advantages to an external DAS. The primary advantage is
related to the mass properties of the dummy. With an internal DAS
system, there are no external cables that may possibly affect body
segment masses; segment masses are always the same no matter how the
dummy is used. While upfront cost is higher, an internal DAS would
reduce per-test costs, eliminate the need for interface cables to lab-
specific DAS systems (which have been a frequent sources of
instrumentation failures in research testing), and reduce the
adjustments needed to arrive at the target test vehicle weight.
Feedback from industry \124\ as well as Euro NCAP indicates that users
prefer an in-dummy DAS for its many usability advantages. Euro NCAP
TB026 requires an in-dummy DAS.\125\ While Euro NCAP TB029 currently
does not specify an approved in-dummy DAS,\126\ earlier versions of
TB029 did specify a few different approved in-dummy DAS systems.\127\
---------------------------------------------------------------------------

\124\ Alliance of Automobile Manufacturers, Inc. (2016).
Technical Considerations Concerning NHTSA's Proposal to Rework the
Agency's New Car Assessment Program (NCAP). <a href="http://Regulations.gov">Regulations.gov</a> Docket
ID NHTSA-2015-0119-0313, available at: <a href="https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf">https://www.regulations.gov/contentStreamer?documentId=NHTSA-2015-0119-0313&attachmentNumber=5&contentType=pdf</a>.
\125\ TB026 Sec. 1.2.
\126\ European New Car Assessment Programme (2022). Euro NCAP
Supplier List, Version 4.0, October 2022, TB 029, available at:
<a href="https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/">https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/</a>.
\127\ European New Car Assessment Programme (2022). Euro NCAP
Supplier List, Version 3.1, April 2021, TB 029, available at:
<a href="https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/">https://www.euroncap.com/en/for-engineers/supporting-information/technical-bulletins/</a>. The DTS TDAS G5, SLICE Nano, and SLICE6; the
Kistler DTI, microDAU, and NXT32; and the Messring M=BUS.
---------------------------------------------------------------------------

In light of these potential advantages and user preferences, NHTSA
sponsored development and testing of an in-dummy DAS. NHTSA published a
request for solicitation for an in-dummy DAS.\128\ This was before Euro
NCAP began testing with the THOR-50M. The solicitation favored a
minimal redesign of existing THOR-50M parts, in order to facilitate
interchangeability of parts between THOR-50Ms with and without in-dummy
DASs. NHTSA contracted Diversified Technical Systems (DTS) to implement
its SLICE6 data acquisition system in a NHTSA-owned THOR-50M. This
included delivery of DAS components, replacement instrumentation
compatible with the DAS, and replacement ATD parts to allow attachment
of DAS components and preservation of inertial properties. The
resulting implementation distributes a series of small 6[hyphen]channel
data acquisition modules throughout the ATD, mounted directly on load
cells or sensors where possible, or close to the sensor with short
cables to the sensor. The DAS modules are chain[hyphen]networked with
four wiring harnesses which connect to the SLICE6 Distributor, with a
single ATD exit cable connecting the DAS to the full test system.
---------------------------------------------------------------------------

\128\ National Highway Traffic Safety Administration (2017).
Implement and Install THOR 50M In Dummy Data Acquisition System.
Solicitation Number DTNH2217Q00033, available at <a href="https://sam.gov/opp/068c7821de797ebe7f9e78a0f2b68dc4/view">https://sam.gov/opp/068c7821de797ebe7f9e78a0f2b68dc4/view</a>.
---------------------------------------------------------------------------

NHTSA evaluated the overall performance and equivalence of the
THOR-50M with the in-dummy SLICE6 DAS in a full suite of qualification
testing and a variety of sled and vehicle crash testing. This research
and analysis is described briefly below. The vehicle crash testing is
described in more detail in the cited report. NHTSA is preparing a
report on the installation, qualification testing, and sled testing of
the SLICE6 in-dummy DAS, which will be placed in the research docket
when it is complete. Additional information on the durability of the
THOR-50M with the in-dummy DAS system is included in Section VII.B,
Durability and Maintenance.
<bullet> It was possible to install the SLICE6 into the dummy with
negligible changes to the mass, moment of inertia, and center of
gravity of the ATD and its individual body segments. This did require
modifications to several THOR-50M parts (e.g., the lower thoracic spine
assembly) in order to allow attachment of the DAS hardware to the rigid
components of the ATD.
---------------------------------------------------------------------------

\129\ Saunders, J., Parent, D. (2023). Update on NHTSA's OMDB's
half barrier analysis. Proceedings of the 27th Enhanced Safety of
Vehicle Conference, Yokohama, Japan.
\130\ The OVSC Laboratory Test Procedures for FMVSS No. 208
specify an ambient temperature measured within 36 inches of the ATD
to be between 69 and 72 degrees Fahrenheit. National Highway Traffic
Safety Administration (2008). Laboratory Test Procedure for FMVSS
208, Occupant Crash Protection, TP208-14, available at: <a href="https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/tp-208-14_tag.pdf">https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/tp-208-14_tag.pdf</a>.
---------------------------------------------------------------------------

<bullet> NHTSA has been able to fully qualify THOR-50M ATDs with
the in-dummy DAS installed. Since the SLICE system has been installed,
we have used the dummy in many tests and have qualified it with no
issues. The THOR-50M with the in-dummy DAS was tested in simplified
sled tests. Sled tests were conducted in the Gold Standard 1 (40 km/h,
12g peak pulse, standard lap and shoulder belt) and Gold Standard 2
(30km/h, 9g peak pulse, 3kN load limited shoulder belt) test
conditions, which were used both in biofidelity assessment and in the
development of thoracic injury criteria. The goal of this testing was
to determine if any differences occurred between the external and
internal DAS configurations, and if so, whether the magnitude of these
differences would affect the biofidelity and injury criteria
development analyses.
<bullet> NHTSA also tested the THOR-50M with an in-dummy DAS in a
series of vehicle crash tests in the OMDB test condition with three
different deformable barrier faces. While some of the OMDB tests
appeared to show differences between the in-dummy DAS and umbilical
configurations, it was not clear whether this was due to variation in
the dummy response or variation in dummy positioning, vehicle response,
and/or restraint system response.\129\
Importantly, this testing did not reveal any potential durability
or usability issues associated with the in-dummy DAS, with one possible
exception: The temperature inside the thoracic cavity of the ATD can
increase beyond the ambient temperature typically prescribed for
regulatory and consumer information crash tests.\130\ In a more recent
set of vehicle crash tests, NHTSA closely monitored the rib temperature
of the THOR-50M with the

[[Page 61915]]

in-dummy DAS.\131\ By routinely limiting the ``ON'' time of the DAS,
NHTSA has been able to maintain the temperature range. Additionally,
NHTSA has used a portable fume extractor device to aid in maintaining
the temperature of the WorldSID-50M side impact dummy, which also has
internal DAS system.132 133 This device may also be employed
in tests with the THOR-50M.
---------------------------------------------------------------------------

\131\ Saunders, J., Parent, D., Martin, P. (2023). THOR-50M
fitness assessment in FMVSS No. 208 unbelted crash tests.
Proceedings of the 27th Enhanced Safety of Vehicle Conference,
Yokohama, Japan.
\132\ Tatem, W., Louden, A. (2023). WorldSID-50M Fitness
Assessment in FMVSS No. 214 Moving Deformable Barrier and Oblique
Pole Crash Tests. Proceedings of the 27th Enhanced Safety of Vehicle
Conference, Yokohama, Japan.
\133\ This device is used to dissipate heat from the dummy in
the pre-test setup (for example, while seating and positioning the
dummy). Typically, a tube is inserted into the dummy jacket and in
conjunction with the fan is used to vent heat from the dummy to
maintain an in-spec internal temperature. The apparatus is detached
from the dummy immediately prior to the vehicle or sled test. Use of
such a fan may be specified in the OVSC laboratory test procedure.
---------------------------------------------------------------------------

Based on this testing, NHTSA has tentatively concluded that the
THOR-50M with the in-dummy DAS is equivalent to one with the external
DAS. NHTSA is therefore proposing an internal DAS as permitted optional
instrumentation that it could use in its testing. This necessitates
changes to the dummy to accommodate the DAS while ensuring that there
are no changes to the mass, moment of inertia, and center of gravity of
the ATD and its individual body segments. These changes may differ from
the Euro NCAP approach specified in TB026, which permits the four-
position spine box (discussed in Section III.H above) to accommodate
the installation of some DAS brands by providing a mounting surface for
data loggers. Euro NCAP does not provide part-by-part engineering
drawings of the various DAS packages, which is necessary for THOR-50M
to be sufficiently objective.
NHTSA has therefore provided, in an addendum to the 2023 drawing
package, further specifications for the dummy to accommodate an
internal DAS. It is anticipated that, upon finalization of this
proposal, the in-dummy DAS drawings will be fully integrated within the
relevant technical data package components. These specifications
consist of descriptions of the instrumentation and new drawings for the
dummy parts that require modifications to accommodate the DAS. The
changes are specified such that the dummy with the in-dummy DAS will
have the same inertial properties as the dummy using the external DAS.
The drawings show DAS mass blanks in lieu of the actual DAS components
(battery, data logger, etc.) with the exterior dimensions of the blank
matching those of the corresponding SLICE6 component.
If an in-dummy DAS component is not installed (for example, if
lower leg instrumentation is not needed for a given test mode), the
blank would be filled with a material of a specified density. The
material of the blank is not specified (although a reference
specification is provided) but would be selected to provide an
appropriate density and may also have internal flashing holes needed to
attain the desired mass, which is chosen to match the mass of the
actual DAS component. It is anticipated that, upon finalization of this
proposal, the PADI will show two sets of installation steps: one with
the ``blank'' component, and one with the actual DAS parts. (This two-
set convention is also followed with load cells and their structural
replacements). The proposed specifications are based on, but not
necessarily limited to, the SLICE6 (the SLICE6 is not explicitly
specified or called-out by name), so that another system fitting within
the defined specifications could also be utilized.\134\
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\134\ While we are aware of in-dummy DASs produced by other
manufacturers, we have not evaluated whether these systems would be
compatible with the in-dummy DAS addendum to the 2023 drawing
package.
---------------------------------------------------------------------------

NHTSA seeks comment from users who have experience with both
umbilical and in-dummy DAS configurations of the THOR-50M, as to
whether they have seen any quantifiable differences between the two.
NHTSA also seeks comment on whether any additional changes should be
made to the proposed drawings specifying the in-dummy DAS to make it
more amenable to additional DAS systems that are already in the field.

IV. Biofidelity

Biofidelity is a measure of how well the dummy replicates a human,
and includes anthropometry, mass properties, range of motion, and
impact response. The impact biofidelity is evaluated by comparing the
response of the dummy to the response of a post-mortem human surrogate
(PMHS or cadaver) or human volunteer in a variety of different test
conditions (also referred to as test modes). Some of these tests focus
on individual dummy components (head, neck, chest, abdomen, upper leg,
knee, lower leg) and some evaluate the entire dummy as a complete
assembly.
To evaluate the biofidelity of THOR-50M, NHTSA selected test
conditions based on relevance to frontal and frontal oblique crash test
applications and the availability of data. For example, a neck frontal
flexion test was conducted by attaching the base of the THOR-50M neck
to a sled and applying a certain acceleration pulse. This was then
compared to the response measured on human volunteers who were
subjected to a similar pulse. Specifically, the impact biofidelity of
the THOR-50M was assessed in twenty-one test conditions. The test
conditions are summarized in Table 6. Each test produces a series of
data points (e.g., force vs. time).
The test conditions have been developed over the years by various
researchers to evaluate biofidelity and have been published in peer-
reviewed journals. The PMHS and human volunteer response data generally
comes from this published research. The THOR-50M response data comes
from testing that NHTSA has been conducting on the THOR-50M throughout
its development, all of which is available in NHTSA's Biomechanics Test
Database.\135\ NHTSA also compared THOR-50M's biofidelity to that of
the HIII-50M; many of the tests conducted with THOR-50M were paired
with the same test conducted on the HIII-50M. In our testing we
attempted to match the test conditions as closely as possible to the
test conditions in the original PMHS or volunteer tests.\136\
---------------------------------------------------------------------------

\135\ Available at <a href="https://www.nhtsa.gov/research-data/research-testing-databases#/biomechanics">https://www.nhtsa.gov/research-data/research-testing-databases#/biomechanics</a>.
\136\ Overall, while some assumptions were necessary in the
reproduction of the PMHS or volunteer test conditions, we believe
that these assumptions should not affect the overall biofidelity
assessment of the THOR-50M. For instance, NHTSA simplified some of
the original tests in order to facilitate ease of testing when we
expected the simplification to have a negligible influence on the
result, such evaluating neck flexion using only the ATD's head and
neck, and not the entire dummy. These assumptions and
simplifications, as well as any limitations to our analyses, are
discussed in detail in the docketed biofidelity report. Parent, D.,
Craig, M., Moorhouse, K. 2017. Biofidelity Evaluation of the THOR
and Hybrid III 50th Percentile Male Frontal Impact Anthropomorphic
Test Devices. Stapp Car Crash Journal, 61, 227-276, available at:
<a href="https://www.regulations.gov/document/NHTSA-2019-0106-0004">https://www.regulations.gov/document/NHTSA-2019-0106-0004</a>.

[[Page 61916]]

Table 6--Biofidelity Conditions Considered in the Design of the HIII
Frontal Dummies and THOR-50M ATDs
------------------------------------------------------------------------
Subpart
Body region Test condition E, O, W THOR-50M
------------------------------------------------------------------------
Head......................... Isolated Head Drop... <bullet> <bullet>
Whole-body Head ........ <bullet>
Impact.
Face Rigid Bar....... ........ <bullet>
Face Rigid Disk...... ........ <bullet>
Neck......................... Neck Flexion, <bullet> ........
Pendulum.
Neck Extension, <bullet> ........
Pendulum.
Neck Frontal Flexion, ........ <bullet>
Sled.
Neck Lateral Flexion, ........ <bullet>
Sled.
Neck Torsion......... ........ <bullet>
Thorax....................... Sternal Impact, 6.7 m/ <bullet> ........
s.
Sternal Impact, 4.3 m/ ........ <bullet>
s.
Lower Ribcage Oblique ........ <bullet>
Abdomen...................... Upper Abdomen ........ <bullet>
Steering Rim.
Lower Abdomen Rigid ........ <bullet>
Bar.
Abdomen Belt Loading. ........ <bullet>
KTH.......................... Femur Compression.... <bullet> <bullet>
Knee Shear........... <bullet> <bullet>
Lower Extremity.............. Dynamic Heel Impact.. ........ <bullet>
Tibia Axial ........ <bullet>
Compression.
Dynamic Dorsiflexion. ........ <bullet>
Whole-body................... Gold Standard 1...... ........ <bullet>
Gold Standard 2...... ........ <bullet>
Gold Standard 3...... ........ <bullet>
Far Side Oblique..... ........ <bullet>
------------------------------------------------------------------------

The test conditions used to evaluate the THOR-50M represent an
accumulation of biomechanics research. All conditions are accompanied
by a well-specified, objective test procedure and a well-founded set of
human response targets. The set of test conditions has grown
substantially over the span of Part 572 rule makings. For example, in
NHTSA's original 1998 proposal for the Subpart O HIII-5F dummy,\137\
only six biofidelity conditions were assessed.\138\ Since then, the
list has grown substantially; new conditions have been developed for
all body regions, and whole-body sled test conditions have been
developed.\139\
---------------------------------------------------------------------------

\137\ 63 FR 46981.
\138\ Mertz, H.J., Irwin, A.L., Melvin, J.W., Stanaker, R.L., &
Beebe, M. (1989). Size, weight and biomechanical impact response
requirements for adult size small female and large male dummies (No.
890756). SAE Technical Paper.
\139\ See National Highway Traffic Safety Administration,
``Biomechanical Response Requirements of the THOR NHTSA Advanced
Frontal Dummy, Revision 2005.1,'' Report No: GESAC-05-03, U.S.
Department of Transportation, Washington, DC, March 2005 (available
at <a href="http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf">http://www.nhtsa.gov/DOT/NHTSA/NVS/Biomechanics%20&%20Trauma/THOR-NT%20Advanced%20Crash%20Test%20Dummy/thorbio05_1.pdf</a>) and
Ridella, S., Parent, D., ``Modifications to Improve the Durability,
Usability, and Biofidelity of the THOR-NT Dummy,'' The 22nd
International Technical Conference for the Enhanced Safety of
Vehicles, Paper No. 11-0312, 2011.
---------------------------------------------------------------------------

NHTSA quantified how closely the response of the THOR-50M matched
the response of the PMHS or human volunteers using the Biofidelity
Ranking system (BioRank).\140\ BioRank has been applied in other
instances cited in the literature \141\ and in other NHTSA Part 572
rulemakings.\142\ This methodology statistically compares the dummy
response to the average PMHS/volunteer response (typically a time-
series but sometimes a point estimate). A BioRank value of 0.0
indicates an ATD response identical to the average PMHS/volunteer
response; a value of 1.0 indicates an ATD response that is on average
one standard deviation \143\ away from the average PMHS/volunteer
response; a value of 2.0 indicates an ATD that is on average two
standard deviations away from the average PMHS/volunteer response; and
so on. Therefore, the lower the BioRank value, the better the
biofidelity. We computed BioRank scores for both the THOR-50M and the
HIII-50M.
---------------------------------------------------------------------------

\140\ Rhule, H., Maltese, M., Donnelly, B., Eppinger, R.,
Brunner, J., Bolte, J. (2002) Development of a New Biofidelity
Ranking System for Anthropomorphic Test Devices. Stapp Car Crash
Journal 46: 477-512.
\141\ Rhule, H., Moorhouse, K., Donnelly, B., Stricklin, J.
(2009) Comparison of WorldSID and ES-2RE Biofidelity Using Updated
Biofidelity Ranking System. 21st ESV Conference, Paper No.09-0563.
\142\ The analysis using Biorank described here mirrors (with
some exceptions) the approach used in the assessment of the WorldSID
50th ATD. See, e.g., 80 FR 78522, 78538 (Dec. 16, 2015) (New Car
Assessment Program Request for Comments); 71 FR 75304 (Dec. 14,
2006) (final rule for ES-2re Side Impact Crash Test Dummy 50th
Percentile Adult Male); 71 FR 7534 (Dec. 14, 2006) (final rule for
SID-IIs Side Impact Crash Test Dummy 5th Percentile Adult Female).
\143\ The standard deviation is a statistic that measures the
dispersion of a dataset relative to its mean.
---------------------------------------------------------------------------

For each body region, we calculated two BioRank scores: one for
external biofidelity (the extent to which the ATD represents a human
surrogate to the vehicle or restraint system); and one for internal
biofidelity (the ability of the ATD to represent the human responses
that relate to prediction of injury). External biofidelity measures are
generally those recorded at the test fixture level, such as pendulum
force or belt force; internal biofidelity measures are generally those
recorded by the internal instrumentation of the ATD or test equipment
such as motion tracking that records subject excursion.
NHTSA considered two other methods of quantifying biofidelity. One
is the International Standards Organization (ISO) 9790 Biofidelity
Classification System. ISO 9790 defines the analysis process, response
corridors, and weighting factors for the quantitative assessment of
biofidelity of side impact ATDs. Because the ISO 9790 response
corridors and weighting factors are specific to side-impact ATDs, it
could not be directly applied to a frontal impact ATD such as the THOR-
50M, and we are not aware of a corollary ISO standard for assessment of
frontal impact ATD biofidelity. While a method similar to that
described in ISO 9790 could be developed to assess frontal impact ATD
biofidelity, we believe such a method may introduce subjective bias
because it contains many subjective features, including weighting

[[Page 61917]]

of test conditions and body regions.\144\ The BioRank system was
developed to minimize subjectivity in the areas of corridor
development, weighting, and scoring. Another method NHTSA considered is
correlation and analysis (CORA), which may be a useful tool to carry
out quantitative analysis.\145\ However, the vast array of tunable
parameters in the software can result in unintentional subjectivity and
poor reproducibility. Further, there are no known and accepted
relationships between CORA scores and biofidelity classifications.
Accordingly, we evaluated biofidelity using BioRank.
---------------------------------------------------------------------------

\144\ Rhule, D., Rhule, H., Donnelly, B. (2005) The Process of
Evaluation and Documentation of Crash Test Dummies for Part 572 of
the Code of Federal Regulations. 19th ESV Conference, Paper No. 05-
0284, pp. 9-10.
\145\ Gehre C, Gades H, Wernicke P (2009) Objective rating of
signals using test and simulation responses, The 21st International
Technical Conference for the Enhanced Safety of Vehicles, Paper No.
09-0407, 2009.
---------------------------------------------------------------------------

We note that because many of the biofidelity test conditions
utilize specialized instrumentation or test equipment, they are not
intended to be carried out as certification or qualification tests
conducted between crash tests or sets of crash tests to confirm that
specified ATD response requirements are met. Instead, due to its
relative complexity, biofidelity testing is carried out at the ATD
design stage to assess the biofidelity of the design. Simplified and
standardized versions of the biofidelity test conditions have been
developed as qualification procedures for some body regions. Because
the qualification response requirements are based on the expected
variation in response of the ATD, not the underlying human response,
the qualification requirements specify a much smaller allowable range
in response than the biomechanical design targets. Therefore, it is
expected that all THOR-50M units that meet the specifications of the
qualification procedures would demonstrate similar biofidelity. The
proposed qualification response requirements are discussed in Section
V.
A full description of NHTSA's biofidelity testing and analysis can
be found in the docketed biofidelity report.\146\ We note that there
are no separate discussions in the report for the shoulder, spine, or
pelvis. Impact biofidelity of the spine and pelvis, as well as the
dynamic biofidelity of the shoulder, are intrinsically evaluated as
part of the whole-body biofidelity sled test series.\147\ Shoulder
biofidelity has also been assessed quasi-statically and found to be
more similar to the human volunteer corridors than existing ATDs. NHTSA
is finalizing a report on the alternate shoulder design, which includes
the biofidelity evaluation described here; once complete, this report
will be published to the research docket.
---------------------------------------------------------------------------

\146\ Parent, D., Craig, M., Moorhouse, K. 2017. Biofidelity
Evaluation of the THOR and Hybrid III 50th Percentile Male Frontal
Impact Anthropomorphic Test Devices. Stapp Car Crash Journal, 61,
227-276, available at: <a href="https://www.regulations.gov/document/NHTSA-2019-0106-0004">https://www.regulations.gov/document/NHTSA-2019-0106-0004</a>.
\147\ The qualitative biofidelity of the shoulder is also
discussed in the Biofidelity Report, where the role of the shoulder
in belt retention (or lack thereof) is discussed qualitatively. See
p. 272-273.
---------------------------------------------------------------------------

NHTSA believes that the THOR-50M is sufficiently biofidelic for
incorporation into Part 572. The biofidelity report shows that the
THOR-50M exhibits overall internal and external BioRank scores of below
2.0. See Table 7. Both internal and external BioRank scores are lower
than those of the HIII-50M, which is defined in Part 572 (Subpart E)
and used in regulatory and consumer information frontal impact crash
testing. At the body region level, the internal and external BioRank
scores for THOR-50M are all below 2.0 except for neck internal
biofidelity and abdomen external biofidelity. The THOR-50M BioRank
score for the neck and abdomen external biofidelity are, however, lower
(better) than those for the HIII-50M. Overall, the internal BioRank
scores for the THOR-50M were lower than those of HIII-50M in 5 of the 7
body regions evaluated, and THOR-50M external BioRank scores were lower
than those of HIII-50M in 6 of the 7 body regions evaluated. Thus, the
THOR-50M has generally improved biofidelity in the individual body
region tests, which improves the accuracy of injury predictions. The
THOR-50M and the HIII-50M have comparable quantitative biofidelity in
the whole-body sled test conditions.\148\
---------------------------------------------------------------------------

\148\ This finding has been confirmed by independent research; a
2018 study showed that the HIII-50M and THOR-50M demonstrated
similar biofidelity scores in a sled test environment representing a
production vehicle. See Albert, Devon L., Stephanie M. Beeman, and
Andrew R. Kemper. ``Occupant kinematics of the Hybrid III, THOR-M,
and postmortem human surrogates under various restraint conditions
in full-scale frontal sled tests.'' Traffic Injury Prevention
19.sup1 (2018): S50-S58.

Table 7--Body Region Internal and External BioRank Summary
----------------------------------------------------------------------------------------------------------------
THOR-50M HIII-50M
Body region ---------------------------------------------------------------
Internal External Internal External
----------------------------------------------------------------------------------------------------------------
Head............................................ 0.155 1.143 0.013 6.640
Neck............................................ 2.155 1.677 2.185 4.318
Thorax.......................................... 0.917 0.948 1.603 2.070
Abdomen......................................... 1.470 2.803 1.629 3.474
KTH............................................. 1.400 1.731 3.875 6.667
Lower Extremity................................. 1.349 0.871 0.832 1.108
Whole-body...................................... 1.472 1.989 1.576 1.780
---------------------------------------------------------------
Overall..................................... 1.274 1.594 1.673 3.722
----------------------------------------------------------------------------------------------------------------

Since a majority of the test conditions involved pure frontal
loading, and several involved oblique and lateral loading (neck lateral
flexion, neck torsion, lower thorax oblique, Gold Standard 3, and Far
Side Oblique test conditions), these findings are expected to extend to
frontal and frontal oblique crash test conditions. The findings may
not, however, extend to other loading conditions (such as pure lateral
or rear impacts) without further research.

V. Qualification Tests

This NPRM proposes qualification tests (also referred to as
qualification procedures) for THOR-50M. The qualification procedures
describe a series of impact tests performed on a fully-assembled dummy
or dummy sub-assembly. The tests assess the components that play a key
role in the dummy's performance in the intended application of frontal
and frontal oblique crashes. We propose

[[Page 61918]]

qualification tests for the head, face, neck, upper thorax, lower
thorax, abdomen, upper leg, knee, and lower leg. For some body regions
(such as the face) we propose a single test condition (also referred to
as a test mode), while for other body regions (for example, the neck)
we propose a series of different test conditions.
Each qualification test condition consists of test procedures, test
parameters, and acceptance intervals. The test procedures describe a
detailed series of steps that must be carried out to perform the test.
Test parameters describe specific aspects of the dummy's response.
Acceptance intervals (or qualification targets) are specified for each
test parameter. Acceptance intervals are a typically pair of numeric
values (a minimum value and maximum value) within which the dummy
response must fall in order to pass, but can also represent a minimum
or maximum value of the response. For instance, one of the tests
involves striking the head with an impactor and measuring the head's
acceleration, which must be within the acceptance interval 117 <plus-
minus> 11.7 Gs.
The qualification tests mirror the dummy loading patterns observed
in frontal crash tests, including full frontal, oblique, and offset
modes. For the neck assembly, we have specified separate requirements
in flexion, extension, and lateral flexion. These bending modes have
all been observed in crash testing. Additionally, a torsion test is
prescribed for the neck since it also twists along its long axis to
some degree. For the feet and ankles, tests in inversion, eversion,
dorsiflexion, and axial loading through the tibia are specified to
account for the various injurious loads that have been observed in
crash tests. For the head, face, upper and lower thorax, abdomen, upper
legs, and knees, we have only prescribed impact tests to anterior
aspects since injurious loads pass primarily through those aspects
during crash testing. The impact speeds and probe masses have been
selected to demonstrate that the various body segments work properly at
energy levels at or near those associated with high injury risks. For
measurements not associated with an injury criterion, energy levels are
chosen to exercise the dummy approaching its functionality limits, but
without causing damage.
The qualification tests ensure that the dummy is functioning
properly. There are a few inter-related aspects to this. One is that
qualification tests ensure that dummy components and sensors are
properly assembled and functioning. Qualification tests monitor the
response of components that may have become loosened or misaligned
since initial assembly. For each test, certain dummy sensors and signal
characteristics (such as the magnitude and timing) have been specified
as qualification targets. Loose or misaligned parts may become evident
when a signal does not conform to the prescribed signal
characteristics. By monitoring these sensors, the qualification tests
ensure that the dummy is functioning properly. The tests also ensure
that the sensors themselves are working properly. Another aspect is
that qualification tests help identify components that have
deteriorated over time, preventing the dummy from meeting the
qualification targets; such parts need to be replaced or refurbished.
Many of the qualification test protocols are very similar to the
dynamic tests used to assess biofidelity. This helps to ensure that a
qualified dummy is also a biofidelic dummy. Finally, they ensure that
the dummy or particular sub-assembly is responding in a uniform and
expected manner; if it is not, certain dummy components might need to
be tuned or adjusted to obtain a response within the qualification
targets.
NHTSA's experience has shown that the impact tests on body segments
are needed to ensure uniformity of dummy responses in a subsequent
vehicle crash test. In other words, full conformance to part and
assembly specifications (in accordance with the drawings and PADI) is
not enough to guarantee a uniform dummy response in a crash test.\149\
Qualification tests have proven reliable and sound in qualifying
NHTSA's other test dummies. Moreover, some of the proposed
qualification tests use the same test equipment as other ATDs, thus
minimizing the amount of new qualification equipment needed by test
laboratories that may already have such equipment in place for
qualifying other ATDs. Meeting the qualification tests helps ensure
that the dummy is capable of responding properly in a compliance or
research test. This in turn helps to ensure that the dummy is an
objective test device suitable for the assessment of occupant safety in
compliance tests specified in Federal Motor Vehicle Safety Standards,
and for other testing purposes.
---------------------------------------------------------------------------

\149\ At the same time, conformance to a qualification
requirement is not a substitute for parts that do not conform to
drawing specifications.
---------------------------------------------------------------------------

NHTSA proposes setting the qualification targets at <plus-minus>
10% of the mean response for each qualification parameter as reported
in the qualification test R&R study (discussed in Section VI). In that
study we subjected multiple dummies to repeated tests in each test
condition at multiple test laboratories. The repeatability testing and
analysis for the qualification tests is described in more detail in
Section VI.A. We believe that 10% is wide enough to account for normal
variations in ATD and laboratory differences, and narrow enough to
ensure consistent and repeatable measurements in standardized testing
with the ATD. This is also consistent with the qualification limits for
the other Part 572 ATDs. For example, for the Hybrid III 10-year-old
child dummy, the acceptance intervals are, on average, set at <plus-
minus>9.9% from the nominal midpoint, with a low of 8.4% (neck rotation
in the neck extension test) and a high of 10.8% (in the neck moment in
the extension test and chest deflection in the thorax impact
test).\150\ For all Part 572 ATDs, the average acceptance interval is
<plus-minus>11%.
---------------------------------------------------------------------------

\150\ HIII-10C, Subpart T.
---------------------------------------------------------------------------

We also considered setting the qualification targets at plus or
minus two standard deviations from the mean response observed in the
testing reported in the repeatability and reproducibility study. This
would have narrowed the acceptance interval for almost all responses,
some of which would have been unreasonably narrow. For instance, the
head impact test results in the repeatability and reproducibility study
were very uniform, with a CV for peak force of 0.9%. If the acceptance
interval for peak force were set to plus or minus two standard
deviations (<plus-minus>1.8%), 24 of the 26 trials would have resulted
in a pass; if it were set to <plus-minus>2.5%, all 26 trials would have
resulted in a pass. This result may have been a function of using only
three THOR-50M units in the test series, all of which were brand new
when we tested them. Therefore, we propose a greater allowance of
<plus-minus>10% for all qualification requirements to account for
slight variations that may arise from equipment and testing variations
at different test labs as well as a future population of THOR-50M units
from dummy manufacturers in which lot-to-lot differences in the
fabrication of parts from the same manufacturer may exist. It also
allows for slight changes to individual THOR-50M units over time,
either due to aging of polymeric components or wear and tear under
normal use. Table 8 summarizes the proposed THOR-50M qualification
requirements.

[[Page 61919]]

Table 8--Proposed THOR-50M Qualification Requirements
----------------------------------------------------------------------------------------------------------------
Acceptance
Test Measurement Units Nominal target interval
----------------------------------------------------------------------------------------------------------------
1. Head Impact.................. Peak Probe Force....... N................. 5580 5022-6138
Peak Head CG Resultant G................. 117.0 105.3-128.7
Acceleration.
2. Face Impact.................. Peak Probe Force....... N................. 7098 6378-7796
Peak Head CG Resultant G................. 138 124-152
Acceleration.
3. Neck Flexion................. Peak Upper Neck My..... N-m............... 31.0 27.9-34.1
Upper Neck Fz Most N................. 860 774-946
Positive Value Prior
to 40 ms.
Peak Head Angular deg/sec........... 1975 1777-2172
Velocity vy (relative
to earth).
Peak Head Rotation deg............... 64.5 58.1-71.0
(relative to pendulum).
4. Neck Extension............... Peak Upper Neck My..... N-m............... 23.0 20.7-25.3
Peak Upper Neck Fz..... N................. 2918 2626-3210
Peak Head Angular deg/sec........... 2061 1855-2267
Velocity vy (relative
to earth).
Peak Head Rotation deg............... 65.0 58.5-71.5
(relative to pendulum).
5. Neck Lateral................. Upper Neck Mx first N-m............... 49.7 44.8-54.7
peak after 40.0 ms.
First Peak Head Angular deg/sec........... 1362 1226-1498
Velocity vx (relative
to earth).
Peak Head Rotation deg............... 41.7 37.6-45.9
(relative to pendulum).
6. Neck Torsion................. Peak Upper Neck Mz..... N-m............... 41.4 37.3-45.6
First Peak Upper Neck deg/sec........... 1390 1251-1529
Angular Velocity vz
(relative to earth).
Peak Neck Fixture deg............... 47.9 43.1-52.7
Rotation.
7. Upper Thorax................. Peak Probe Force....... N................. 3039 0-3039
Peak Upper Resultant mm................ 53.6 48.3-59.0
Deflection.
Difference Between Peak mm................ 0 -5 to 5
Left & Right Resultant
Deflections.
Force at Peak Resultant N................. 2677 2409-2944
Deflection.
8. Lower Thorax................. Peak Probe Force....... N................. 3484 3136-3832
Resultant Deflection at mm................ 50.9 45.8-56.0
Peak Force.
9. Lower Abdomen................ Peak Probe Force....... N................. 2918 2626-3210
Lower Abdomen X-axis N................. 83.0 74.7-91.3
Deflection at Time of
Peak Force.
Difference Between Peak mm................ 0 -8 to 8
Left & Right X-axis
Deflections.
10. Upper Leg................... Peak Probe Force....... N................. 8333 7500-9166
Peak Femur Force, Fz... N................. 4920 4428-5412
Peak Resultant N................. 2738 2464-3012
Acetabulum Force.
11. Knee........................ Peak Femur Z-axis Force N................. 6506 5855-7156
Knee Deflection at Peak mm................ 20.2 18.2-22.2
Femur Force.
12. Ankle Inversion............. Peak Lower Tibia Fz.... N................. 505 454-555

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