36 CFR 1004.15: Safety belts.

(a) Each operator and passenger occupying any seating position of a motor vehicle in the area administered by the Presidio Trust will have the safety belt or child restraint system properly fastened at all times when the vehicle is in motion. The safety belt and child restraint system will conform to applicable United States Department of Transportation standards.

(b) This section does not apply to an occupant in a seat that was not originally equipped by the manufacturer with a safety belt nor does it apply to a person who can demonstrate that a medical condition prevents restraint by a safety belt or other occupant restraining device.