Search Interpretations


    Mr. A. Bret Miller
    Director, Quality Control and Certification
    Cool City, Inc.
    10655 Mineral Wells Highway
    Cool, TX 76088

    Dear Mr. Miller:

    This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard (FMVSS) No. 122, Motorcycle Brake Systems. You wish to know whether a prototype design of a three-wheeled motorcycle would meet FMVSS No. 122s requirement for "a parking brake of a friction type with a solely mechanical means to retain engagement." As explained below, the answer is no.

    The National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs for new motor vehicles and new items of motor vehicle equipment. NHTSA does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to certify that their vehicles and equipment meet applicable standards.

    In your letter you describe your product, the "Sport Trike," as using "automotive (General Motors) disc brakes on all three wheels with a conventional hydraulic split service (master cylinder) brake system." You described the parking brake as follows:

    The design contemplated for our vehicle would consist of a mechanical lever that would lock in place when applied while simultaneously applying leverage (pressure) to the service brake pedal mechanism to apply and hold the service brakes on all three wheels. The service brakes, while hydraulically applied, are of the standard automotive friction pad/caliper/disc type. This arrangement is quite similar to the method used for parking brake systems found on many aircraft.

    Section S5.1.4, Parking brake, of FMVSS No. 122 states: "Each three-wheeled motorcycle shall be equipped with a parking brake of a friction type with a solely mechanical means to retain engagement."

    We have reviewed the written description of your parking brake design, which describes the service brakes on each of the three wheels as "hydraulically applied." We have also reviewed the drawing. Based on the drawing, we note that although the parking brake is actuated by a mechanical lever, the parking brake in fact is retained by hydraulic means. S5.1.4 specifies that a three-wheeled motorcycle must have a parking brake of a friction type "with a solely mechanical means to retain engagement." (Emphasis added.) The requirement for a three-wheeled motorcycle to have a parking brake with "solely mechanical means to retain engagement" would preclude a parking brake design relying even in part on hydraulics for retention of engagement. Thus, a three-wheeled motorcycle with your proposed parking brake design would not meet FMVSS No. 122.

    The confidential drawing you provided has been returned under separate cover.

    I hope this information is helpful. If you have any further questions, please feel free to contact Dorothy Nakama of my staff at this address or by telephone at (202) 366-2992.


    Jacqueline Glassman
    Chief Counsel