To reduce the number of deaths and injuries from light vehicles crashing into the back of semi-trailers, the Department of Transportation requires trailers and semi-trailers to have bumpers or rear impact guards. The bumper must meet the Federal Motor Vehicle Safety Standard requirement that was in force when the truck was manufactured. The requirement does not apply to pole trailers, pulpwood trailers, low chassis, special-purpose, wheels back vehicles, and trailers transported in a drive-away/towaway operation.
Rear impact guards must be attached to the semi-trailer's chassis by the manufacturer of the trailer in accordance with the installation procedures provided in the Federal Motor Vehicle Safety Standard No. 223, which details the rules for rear impact guards. The semi-trailer must also match the type of vehicle identified in the installation instructions as the type for which the rear impact guard being installed was made.
Size and Position
The bumper must extend horizontally to within 4 inches of the side of the truck and not beyond. The distance between the bottom of the bumper and the ground must not exceed 22 inches at any point. The rear surface of the bumper must be within 12 inches of the rear surface of the truck, and the height of the bumper must be at least 3.94 inches.
Certification and Labeling
Each bumper must be labeled or permanently marked on the outside area 12 inches in from the right side so that it may be easily seen. Information of the label or marking must contain the bumper manufacturer's name and address, the month and year it was manufactured, and the letters "DOT," certifying that the bumper conforms to all requirements of the Federal Motor Vehicle Safety Standard. All semi-trailers, regardless the state they're in, must have this federal certification on the bumper. The manufacturer of the bumper must be contacted in the case of a bumper not being labeled.
If the semi-trailer bumper is damaged in an accident, it must be repaired. If the damage is minor and consists of merely small bends, it may be straightened. Other damaged pieces must be replaced, and all replacement pieces must be primed and painted to match the original bumper and parts. All repairs and replaced parts on semi-trailers newer than 1998 must meet federal standards. The bumpers also must have the label or marking certifying that they meet DOT requirements.