Kingpin to rear axle requirements

While 23 CFR Part 658 requires states to accept 48-foot trailers, trailers over 48 feet in length are allowed throughout the United States. However, states can have rules restricting the configuration of these trailers (such as length and wheelbase limits) and restricting the roads they can operate on. Restricting the distance from the trailer kingpin to trailer rear axle(s) is a common restriction. The purpose behind the kingpin-to-axle(s) requirements are to keep the turning radius of a 53-foot trailer similar to that of a shorter trailer.

Scope

All carriers and drivers that operate trailers that are over 48 feet in length are covered by these requirements.

Regulatory citations

23 CFR Part 658 — Truck Size and Weight, Route Designations — Length, Width and Weight Limitations
State size and weight limits

Key definitions

Kingpin to front axle: A measurement from the kingpin on the trailer to the center of the front axle on the trailer. Note: Some states will refer to the “center of the axle” as “the point where the wheels on the axle are in contact with the road surface.”
Kingpin to rear axle: A measurement from the kingpin on the trailer to the center of the rear axle on the trailer.
Kingpin to the center of the rear axle group: A measurement from the kingpin on the trailer to the center of the group of rear axles on a trailer with multiple axles. This is also referred to as the point midway between two axles.

Summary of requirements

The following apply to all highways within a state unless otherwise specified:

State	Kingpin to Rear Axle Limit
Alabama	41 ft to the rearmost axle or a point midway between the two rear axles (only applies to semitrailers greater than 53 ft 6 in).
California	40 ft to rearmost axle if semitrailer has two or more axles 38 ft to rear axle if semitrailer has one axle and does not extend forward of the rear of the cab.
Connecticut	43 ft between kingpin and center of rearmost axle with wheels in contact with the road surface - allowed on U.S. and CT Routes 1 to 399, 450, 476, 508, 693, and 695, and Interstates and designated routes only.
Florida	41 ft between kingpin and the center of the rear axle or rear group of axles on all roads except roads on the State Highway System that are restricted by the DOT or roads restricted by local authorities.
Illinois	On Class I and II highways, 45 ft 6 in. to the center of the rear axle (applies to trailers greater than 48 ft). On Class III and other non-designated state highways, 42 ft 6 in. to the center of the rear axle.
Indiana	43 ft to the rearmost axle of the semitrailer (only applies to semitrailers longer than 48 ft 6 in).
Maine	43 ft to the center of the rearmost axle (overall length not to exceed 74 ft on non-National Network highways).
Maryland	41 ft to the center of the rear tandem axles - allowed on Interstates and designated routes only.
Michigan	37.5 to 40.5 ft (± 0.5 ft) to the center of the rear axle or the center of the rear axle assembly - allowed on Interstates and designated highways only (applies to semitrailers longer than 50 ft).
Minnesota	43 ft to the centerline of the rear axle group.
New Hampshire	41 ft to the centerline of the rear axle or the midpoint of a tandem axle of the semitrailer - allowed on Interstates and designated highways only.
New Jersey	41 ft to the centerline of the rear axle or rear axle group - allowed on Interstates and designated highways only.
New York	43 ft to the centerline of the rear axle - allowed on Interstates and designated highways only. In New York City, trailers over 48 ft up to 53 ft only allowed on I-95 between I-287 and I-295, on I-295 between I-295 and I-495, and on I-495 between I-95 and the Nassau-Queens county line; kingpin to center of rear axle or rear axle group limited to 43 ft.
North Carolina	41 ft to the rearmost axle or a point midway between the two rear axles - allowed on Interstates and designated highways only.
Pennsylvania	41 ft to the center line of the rear axle or rear axle group.
Rhode Island	41 ft to the center of the rear axle - allowed on Interstates and designated highways only.
South Carolina	41 ft to the center of the rear axle assembly or to the center of the tandem axle assembly. 46 ft from the kingpin to the center of the rear axle for trailers or semitrailers used primarily to transport vehicles used in connection with motorsports competition events.
Tennessee	41 ft to the rearmost axle or a point midway between the two rear axles.
Vermont	41 ft to the center of the rearmost axle.
Virginia	41 ft to the rearmost axle or a point midway between the rear tandem axles.
West Virginia	37 ft from the rear axle of the truck-tractor and the front axle of the semitrailer - allowed on Interstates and designated highways only.
Wisconsin	43 ft to the center of the rearmost axle or a point midway between tandem axles - allowed on Interstates and designated highways and certain state trunk highways only.

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Kingpin to rear axle requirements

Scope

Regulatory citations

Key definitions

Summary of requirements