• Vehicles operating on the National Network must comply with a width limit of 102 inches.
• FMCSA regulations specify precisely how width overhangs are to be flagged or illuminated.

The “width allowed” varies by state and the route within a state.

Federal size and weight limits are not determined by the Federal Motor Carrier Safety Administration (FMCSA), but by the Federal Highway Administration (FHWA) in 23 CFR, Part 658. What states must allow is found in Section 15.

The Surface Transportation Assistance Act (STAA) established a maximum/minimum width limit of 102 inches, or 8 feet, 6 inches, for the National Network.

What is excluded from the federal width limit?

For most vehicles, width is measured from a point on one side or end of a commercial motor vehicle (CMV) to the same point on the opposite side or end of the vehicle, plus any part of a load that is overhanging the vehicle. However, many non-property-carrying devices are not included in the length calculation.

These exclusions are found in:

• 23 CFR 658.16
• Appendix D of Part 658

How must width overhangs be identified?

The FMCSA permits the allowed size and weight, but has regulations regarding how overhangs must be flagged or illuminated.

Side overhangs of more than 4 inches

• When headlamps are required:
  • On the front edge of the overhang — an amber light visible from both the front and side.
  • On the outermost extremity’s rear edge of the overhang — a red light visible from both the rear and side.
  • If the overhang’s length is 3 feet or less, the overhang can be marked with a single amber light visible from the front, both sides, and rear. However, if the overhang is located near or at the rear of the vehicle, a red light visible from the front, side, and rear is used.

• When headlamps are not required, the maximum width is marked with an 18-inch red or orange fluorescent warning flag.