Yes. Section 393.93 of the FMCSRs (49 CFR 393.93) requires seat belts on trucks, truck tractors, and buses manufactured on or after January 1, 1965.  For vehicles built on or after July 1, 1971, the seat belts must comply with the applicable National Highway Traffic Safety Administration's Federal Motor Vehicle Safety Standards dealing with seat belts (49 CFR 571.208, 571.209, and 571.210). Truck drivers, managers, and owners must also always check with the U.S. Department of Transportation and your state and local transportation authorities to ensure that you comply with the most recent rules, regulations, and laws.