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Questions and Answers About Vehicle Size and Weight



May States allow vehicle weight tolerances above Interstate System weight limits?

No. Federal law specifically prohibits this. Interstate weight limits must include all enforcement tolerances.

May States allow scale tolerances?

States may allow up to a 5-percent tolerance for portable scales (wheel-load weighers).

May States allow weight tolerances on the non-Interstate System portions of the Federal-aid Primary, Federal-aid Secondary, and Federal-aid urban systems?

Yes, but they must be authorized by State law or regulations since States must certify annually that they are enforcing their weight laws and regulations on these systems which, prior to October 1, 1991, were designated as Federal-aid primary, Federal-aid secondary, and Federal-aid Urban.

Which Federal agency has jurisdictional and regulatory responsibility for the routing of hazardous material?

As of October 1, 2000, it is the Federal Motor Carrier Safety Administration.

Are there any Federal height requirements for commercial motor vehicles?

No, States may set whatever height limits they believe are appropriate. Typically, the height limits range between l3' 6" and 14'.

Is U.S. 93 across Hoover Dam on the NN?

U.S. 93 on the Arizona side of the dam is not on the NN. However, in Nevada it is on the NN up to where the Bureau of Reclamation jurisdiction begins. The dam itself is owned by the Bureau of Reclamation which has authority to establish traffic regulations on the highway across the dam and could prohibit commercial motor vehicles from using it if they chose to do so.

How may size and weight numerical units be converted to metric units?

The FHWA published a Notice of Interpretation on October 6, 1994 (59 FR 51060) explaining how size and weight requirements may be converted into metric units.

What is a permit?

A permit is an exceptional authorization issued to a motor carrier allowing it to transport oversize or overweight cargo. It is available for a limited period of time and tailored to the needs of each particular vehicle or load.

May States issue overwidth permits "by operation of law" for vehicles on the National Network and reasonable access routes?

No, because it would be a permanent exemption issued unilaterally without evaluating the safety of a vehicle or even requiring an application.

Are there any Federal size and weight regulations for pilot cars?

No. They are subject to State regulation.

May a State participate in a joint port of entry that is wholly within another State?

Yes. However, there may be legal questions regarding the ability of one State to successfully prosecute overweights when the weighing facility is located in a neighboring State. Utah and Arizona and some other States maintain joint ports.

May radar detectors be used in commercial motor vehicles?

No. The FHWA issued a Final Rule December 21, 1993 (58 FR 67370) prohibiting them (This is a safety regulation that is now under the jurisdiction of the Federal Motor Carrier Safety Administration).

Is there a national speed limit?

No. The national speed limits were eliminated in 1995 and responsibility for speed control reverted to the States.

May commercial motor vehicles operate on the 22 miles of U.S. 191 that goes through the northwest corner of the Park?

Yes. The National Park Service published a Final Rule on August 25, 1994 (59 FR 43731) which provided that commercial motor vehicles may operate on this highway, except vehicles transporting hazardous materials must secure a permit from the Park Superintendent (36 CFR 7.13).

Where are federal regulations on vehicle size and weight published?

Federal regulations involving vehicle size and weight are published in 23 CFR 658. This part includes a list of highways in each state that are part of the National Network.
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