DOT Trucks: The U.S. Department of Transportation, via the Federal Motor Carrier Safety Administration, regulates most commercial trucking in the United States, while allowing individual states and jurisdictions to set truck regulations on most state roads. All large trucks which includes the Interstate system and hundreds of other U.S. highways, must adhere to the certain specifications set by the USDOT.[/box]
Most commercial motor vehicles traveling on the National Network must adhere to a gross vehicle weight, or GSV, limit of 80,000 lbs. In addition, the weight supported by any single axle cannot exceed 20,000 lbs., and the weight supported by tandem axles cannot exceed 34,000 lbs. Trucks must also adhere to the Bridge Gross Weight Formula, which takes into account axle number and spacing, ensuring a weight distribution that puts less stress on roads and bridges.
For the most part, each state can set its own length limits on CMVs traveling within that state. However, federal law restricts each state from imposing too low of a maximum length limit on commercial trucks, in certain configurations. The FMCSA bars states from imposing “a length limitation of less than 48 feet on a semitrailer operating in a truck tractor-semitrailer combination” or “less than 28 feet on any semitrailer or trailer operating in a truck tractor-semitrailer-trailer combination.”
The width limit of all commercial motor vehicles traveling on the National Network, with the exception of Hawaii, is 102 inches. As of 2010, Hawaii retains its old 108-inch width limit for CMVs on National Network roads within the state.
The FMCSA still allows oversized semitrailers and trailers in “actual and lawful” use on December 1, 1982, within certain restrictions, to operate on the National Network. The maximum allowed lengths of these grandfathered trailers ranges from 48 feet to 59.5 feet, depending on the particular state.
Longer Combination Vehicles
A truck tractor with either two or three trailers/semitrailers that exceeds the 80,000-lb. weight limit rates as a longer combination vehicle, or LCV. In 1991, each state’s weight and length limit for these over-sized trucks was frozen. In effect, the LCV weight/size limits in the 26 states that allowed LCVs have stayed the same, while LCVs remain banned in states that did not allow their use before 1991. Colorado allows the longest LCVs, at up to 115.5 feet, and Montana allows the heaviest, at a maximum of 137,800 lbs.[/box]