102 Inches Is a Ceiling and a Floor at the Same Time
Date Published
Most federal size and weight rules set a maximum that states may go below. The width rule does something different, and the difference is why 102 inches is so uniform across the country.
The provision
Under 23 CFR 658.15, no state shall impose a width limitation of more or less than 102 inches on a commercial motor vehicle operating on the National Network.
More or less. A state may not allow a wider vehicle, and it may not require a narrower one. The figure is fixed in both directions, which is unusual in a body of law that generally sets floors and lets states build on them.
Hawaii is permitted to keep a 108-inch maximum, the one carve-out in the provision.
Why the symmetry exists
A ceiling alone would leave a carrier able to run wider in a permissive state and be stopped at the line. A floor alone would let a state force a narrower vehicle and effectively close the network to standard equipment. Fixing the figure in both directions is what makes a 102-inch trailer usable coast to coast without a permit.
What is excluded from the measurement
Safety devices and appurtenances are excluded from the width measurement, which is why mirrors and certain other fittings do not by themselves make a vehicle oversize.
Where the National Network ends
The rule applies on the National Network, which comprises the Interstate System plus designated additional routes. Off that network, state law governs, and a vehicle legal on the Interstate may need a permit on a state road leading to the same destination.
That boundary is the most common source of confusion about width. The question is not whether the vehicle is 102 inches; it is whether the road is on the network.
Permits are a state matter
Federal law grants states the power to issue oversize and overweight permits for non-divisible loads. The thresholds, the fees and the escort requirements are state law, are not harmonised, and are one of the least uniform areas of trucking regulation in the country.