49 C.F.R. § 393.203 Cab and body components.
Title 49 - Transportation
(a) The cab compartment doors or door parts used as an entrance or exist shall not be missing or broken. Doors shall not sag so that they cannot be properly opened or closed. No door shall be wired shut or otherwise secured in the closed position so that it cannot be readily opened. (b) Bolts or brackets securing the cab or the body of the vehicle to the frame shall not be loose, broken, or missing. (c) The hood must be securely fastened. (d) All seats must be securely mounted. (e) The front bumper must not be missing, loosely attached, or protruding beyond the confines of the vehicle so as to create a hazard.
Title 49: Transportation
PART 393—PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION
Subpart J—Frames, Cab and Body Components, Wheels, Steering, and Suspension Systems
§ 393.203 Cab and body components.