Special assessments for curbs and gutters levied — Property abutting 2 or more streets, avenues, or roads.

When any property abuts 2 or more streets, avenues, or roads, the assessments against said property levied hereunder shall not exceed in the aggregate, together with any legal assessments heretofore levied and paid for paving, curbing, and guttering of or on said streets, avenues, or roads, under the authority of §§ 9-401.09, 9-401.10, relating to assessments for the paving of streets, avenues, and roads, or under § 9-401.04, relating to assessments for laying curbs, or under §§ 9-421.01 to 9-421.04, 31/2 cents per square foot of area of said property, or 20 per centum of the value of said property, exclusive of improvements thereon, as assessed for the purpose of taxation at the time of the laying of the curb or gutter or curb and gutter for which said assessment is levied.