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Questions and Answers About Vehicle Size and Weight

23 CFR 658.5 Definitions

23 CFR 658.5 Definitions

What is an automobile transporter?

It is a vehicle combination designed and used specifically to transport assembled highway vehicles including truck camper units on both its power unit and semitrailer.

What vehicles may automobile transporters carry to qualify as such?

They may transport assembled highway vehicles including truck camper units that are not self propelled, provided they are capable of operating on highways, i.e., they must have wheels, except wheel-less units designed to be loaded on the bed of a pickup truck may also be transported. They may not transport wrecked automobiles or those used solely to compete in motorsports competition since neither could legally operate on highways, as noted in a Final Rule published December 22, 1998 (63 FR 70650).

Is a noncargo carrying power unit and a semitrailer designed and used to carry automobiles an automobile transporter?

No. It is a truck tractor-semitrailer combination. A semitrailer does not lose its identity as such regardless of its appearance or the cargo it may be carrying.

Does a power unit with an empty head rack pulling a semitrailer configured to transport automobiles qualify as an automobile transporter?

Yes. The presence of a headrack, even though empty, means that the power unit is capable of carrying cargo.

May automobiles be transported on noncargo-carrying truck tractor-semitrailer combinations as well as on automobile transporters?

Yes. Unlike automobile transporters that may transport only automobiles, noncargo-carrying truck tractor-semitrailer combinations may carry any type of cargo including automobiles. States would be free to regulate the length of cargo allowed to overhang the front or rear of such combinations.

May automobile transporters transport freight other than automobiles?

No. If they should, on rare occasions, transport something other than automobiles, they would lose their identity as such and, due to their ability to carry cargo on the power units, would be considered truck-semitrailer combinations.

Is an enclosed 48-foot or longer grandfathered length semitrailer with interior racks that carries automobiles one way and general freight on the return an automobile transporter?

Not unless the power unit is also configured to carry automobiles and then only when carrying automobiles or returning empty.

What are B-trains?

They are truck-tractor semitrailer-semitrailer combinations where the front semitrailer has a fifth wheel hitch mounted on the rear as a hitch for the second semitrailer.

What is a beverage semitrailer?

It is a drop frame semitrailer designed and used to transport bottled or canned beverages (including water) with side-only cargo access.

What is a boat transporter combination?

A vehicle combination designed and used specifically to transport assembled boats and boat hulls that may be partially disassembled to facilitate transportation.

What is a bus?

A bus is a commercial motor vehicle designed or regularly used to carry more than 10 passengers (11 including the driver) but not including vanpools. (Definition of Motor Carriers of Passengers)

What is a dromedary box, deck, or plate?

It is a cargo-carrying unit mounted on the frame of the power unit behind the cab and forward of the fifth wheel hitch.

What types of goods qualifies a carrier as a "household goods carrier?"

Personal effects and property used or to be used in a dwelling by a householder when part of the equipment or supply of such dwelling, as provided in 49 U.S.C. 13102 (10).

What is a longer combination vehicle (LCV)?

It is any combination of a truck tractor and two or more trailers or semitrailers which operates on the Interstate System at a gross vehicle weight greater than 80,000 pounds.

What is a maxi-cube vehicle?

It is a straight truck pulling a semitrailer or trailer, with both units capable of being loaded or unloaded through the trailing unit.

What is the National Network?

It consists of the Interstate System and designated highways on which States must allow vehicles subject to Federal size limits to operate, as shown in Appendix A to 23 CFR 658.

What is the National Highway System?

It is the Federal-aid system on which States may spend Federal Highway funds. It was designated by the States in consultation with the FHWA and includes the Interstate System. It is designed to serve major population centers, international border crossings, ports, airports, public transportation facilities and other major travel destinations.

Do Federal weight and size requirements apply on the National Highway System?

Federal weight limits apply on the Interstate System, which is also part of the National Highway System. Federal size limits apply on the National Network and would apply on the National Highway System only where the same highway was on both systems.

What does nondivisible mean?

It means any load or vehicle exceeding applicable length or weight limits which, if separated into smaller loads or vehicles, would: (1) Compromise the intended use of the vehicle, i.e., make it unable to perform the function for which it was intended; (2) Destroy the value of the load or vehicle, i.e., make it unusable for its intended purpose; or (3) Require more than 8 workhours to dismantle using appropriate equipment. The applicant for a nondivisible load permit has the burden of proof as to the number of workhours required to dismantle the load. A State may (but is not required to) treat emergency response vehicles, casks designed for the transport of spent nuclear materials, and military vehicles transporting marked military equipment or materiel as nondivisible vehicles or loads.

What are recreational vehicles?

They are generally a vehicular-type unit primarily designed as temporary living quarters for recreational, camping, travel, or seasonal use that either has its own motive power or is mounted on, or towed by, another vehicle. (From American National Standards Institute)

Are recreational vehicles subject to Federal size and reasonable access requirements?

No, because they are not commercial motor vehicles.

Are recreational vehicles subject to Interstate axle weight limits?


Are recreational vehicles required to stop at State scale sites?

Each State may set its own requirements.

What is a saddlemount combination?

It is a combination of vehicles where a truck or truck tractor tows one or more trucks or truck tractors, each towed vehicle connected by a saddle to the frame or fifth wheel of the vehicle in front.

May vehicles in a saddlemount combination be towed backwards?

No. The definition specifies that the "saddle" connects the front axle of the towed vehicle to the frame or fifth wheel of the vehicle in front.

Federal regulations require States to allow saddlemount combinations with "up to three" saddlemounted vehicles. Does "up to three" mean two or three?

Three. Unlike other units of measurement, where "up to $3.00" may mean $2.99, motor vehicles are not divisible and "up to three" cannot mean 2.99 vehicles. In this context, the obvious meaning of "up to three" is "as many as three."

What is a fullmount?

It is a smaller vehicle mounted completely on the frame of either the first or last vehicle in a saddlemount combination.

What is special mobile equipment?

They are self-propelled vehicles not designed or used primarily for the transportation of persons or property and incidentally moved over the highways.

What is the significance of the special mobile equipment designation?

Special mobile equipment is excluded from Federal width requirements on the National Network and therefore States may regulate their width (23 CFR 658.7).

Does overwidth special mobile equipment require a permit when transported on a regular commercial motor vehicle?

Yes. Special mobile equipment is excluded from Federal width limits only when moved under their own power. These are normally short movements that pose little hazard to the traveling public. When moved on a CMV, they become like any other high speed, over the road, movement.

Is farm equipment such as plows, rakes, etc. that do not have an integral power unit special mobile equipment when powered by a farm tractor?

Yes. A farm tractor serves as an interchangeable power unit for them.

What are STAA vehicles?

While this term has never been defined, it is used to denote vehicles for which the Surface Transportation Assistance Act of 1982 (STAA) provided width and length requirements. These are principally truck tractor-semitrailer combinations with 48 feet or longer grandfathered length semitrailers and twin trailer combinations where neither exceeds 28 feet in length, plus specialized equipment such as automobile and boat transporters. STAA vehicles must be accorded reasonable access between the NN and terminals and facilities for food, fuel, repairs, and rest.

What is a truck tractor?

It is a noncargo carrying power unit that operates in combination with a semitrailer or trailer. A truck tractor and semitrailer engaged in the transportation of automobiles may transport cargo (motor vehicles) on part of the power unit.

Does a truck tractor with a sleeper cab qualify as noncargo carrying?

Yes. Unlike a dromedary box, a sleeper cab does not carry cargo but is part of the driver's cab.

What highways and vehicles do federal laws and regulations cover?

Federal weight limits apply to all vehicles on the Interstate System. Federal laws and regulations involving length and width of vehicles apply to the National Network, which includes the Interstate System plus other arterial routes designated by the states and the federal government.

What are the National Network and the National Highway System?

The National Network consists of the Interstate System and designated highways on which States must allow vehicles subject to Federal size limits to operate, as shown in Appendix A to 23 CFR 658. The National Highway System is the Federal-aid system on which States may spend Federal Highway funds.
For more information, visit the National Network and National Highway System Web sites.
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