49 C.F.R. § 396.7 : Transportation — OTHER REGULATIONS RELATING TO TRANSPORTATION — FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION — FEDERAL MOTOR CARRIER SAFETY REGULATIONS — INSPECTION, REPAIR, AND MAINTENANCE — Unsafe operations forbidden

(a) General. A motor vehicle shall not be operated in such a condition as to likely cause an accident or a breakdown of the vehicle.
(b) Exemption. Any motor vehicle discovered to be in an unsafe condition while being operated on the highway may be continued in operation only to the nearest place where repairs can safely be effected. Such operation shall be conducted only if it is less hazardous to the public than to permit the vehicle to remain on the highway.

49 C.F.R. §396.7