Interpretation ID: aiam4640
Ohio 44l24;
"Dear Mr. Cantleberry: This responds to your letter concerning Safet Standard No. l05, Hydraulic Brake Systems. You asked several questions about the standard's requirements for parking brakes. Your questions are addressed below. By way of background information, the National Highway Traffic Safety Administration does not provide approvals of motor vehicles or motor vehicle equipment. Under the National Traffic and Motor Vehicle Safety Act, it is the responsibility of the manufacturer to ensure that its vehicles or equipment comply with applicable standards. The following represents our opinion based on the facts provided in your letter. Your first question concerns section S5.2. That section requires specified vehicles to be 'manufactured with a parking brake system of a friction type with a solely mechanical means to retain engagement . . . .' You asked what is meant by a 'parking brake system of a friction type with a mechanical means.' In understanding section S5.2, I believe it is helpful to focus on three aspects of the language quoted above. First, a vehicle must be 'manufactured with a parking brake system.' The term 'parking brake' is defined in 49 CFR Part 57l.3 as 'a mechanism designed to prevent the movement of a stationary motor vehicle.' Second, the required parking brake system must be 'of a friction type,' i.e., it must prevent the movement of a stationary motor vehicle by means of friction. For example, a parking brake which presses a brake shoe against a brake drum operates by friction, whereas the parking pawl of an automatic transmission does not. Third, the required parking brake system must have a 'solely mechanical means to retain engagement.' Thus, the parking brake cannot be held by non-mechanical means such as fluid, air or electricity. Your second question concerns section S5.2.2. You asked whether it is necessary to meet S5.2.2.l, S5.2.2.2, and S5.2.2.3 (i.e., all three subsections) in order to comply with section S5.2.2, or just one of the subsections. Section S5.2.2 provides that '(a) vehicle of a type described in S5.2.l at the option of the manufacturer may meet the requirements of S5.2.2.l, S5.2.2.2, and S5.2.2.3 instead of the requirements of S5.2.l,' if the vehicle has a transmission or transmission control which incorporates a parking mechanism, and the parking mechanism must be engaged before the ignition key can be removed. (Emphasis added.) Given section S5.2.2's use of the word 'and' (as highlighted above), it is necessary to meet the requirements of all three subsections in order to comply with that section's compliance option. You also asked whether a vehicle which has a parking control in the transmission must also have a hand or foot operated control for the brake system. In responding to this question, I assume that the term 'parking control in the transmission' refers to a parking pawl. As noted above, a vehicle manufactured with a parking pawl alone, without an additional parking brake, would not meet section S5.2's requirement that the vehicle be 'manufactured with a parking brake system of a friction type with a solely mechanical means to retain engagement . . . .' Thus, a vehicle which has a parking control in the transmission must also have an additional parking brake 'of a friction type with a solely mechanical means to retain engagement. . . .' Finally, you asked whether a vehicle with a hydraulic locking system would be sufficient to meet the requirements specified in S5.2.2. This question was asked both for a vehicle that has a parking control in the transmission and for a vehicle with a manual transmission. The requirement that a vehicle be 'manufactured with a parking brake system of a friction type with a solely mechanical means to retain engagement' cannot be met by a hydraulic locking system, since such the parking brakes on such a system are held by fluid pressure rather than by 'a solely mechanical means.' Thus, regardless of whether a vehicle has a parking pawl or has a manual transmission, a hydraulic locking system cannot be used to meet Standard No. l05's parking brake requirements. I hope that this answers your questions. Sincerely, Stephen P. Wood Acting Chief Counsel";