Interpretation ID: 22597

Mr. Frank Maloziec
Fiat Auto R&D U.S.A.
39300 Country Club Drive
Farmington Hills, MI 48331-3473

Dear Mr. Maloziec:

This responds to your letter requesting information on Federal Motor Vehicle Safety Standard No. 135, "Light Vehicle Brake Systems." Specifically, you ask whether your Electric Parking Brake (EPB) complies with Standard No. 135. The issues you raise are addressed below.

By way of background information, the National Highway Traffic Safety Administration (NHTSA) does not provide approvals of motor vehicles or motor vehicle equipment. Under 49 U.S.C. Chapter 301, manufacturers are required to ensure that their vehicles and equipment meet applicable requirements. The following represents our opinion based on the facts provided in your letter and subsequent telephone conversation with this office.

Paragraph S5.2 of Standard No. 135 provides: "Each vehicle shall be equipped with a parking brake system of a friction type with solely mechanical means to retain engagement." The term "parking brake" is defined in 49 CFR 571.3 as "a mechanism designed to prevent the movement of a stationary motor vehicle." Thus, the parking brake must prevent the movement of a stationary motor vehicle by means of friction. It also must have a "solely mechanical means to retain engagement," meaning that although the parking brake may be applied and released by non-mechanical means, it must be held by solely mechanical means. It cannot be held by non-mechanical means, such as fluid, air, or electricity.

In your letter, you state that the EPB "differs from the traditional mechanical parking brake mainly by the command used in applying the brake and the way the applied force is transmitted to the disc brakes." The EPB "can be engaged or disengaged by pushing a button fitted in the console." When the "electronic control unit (ECU) which manages the system receives an input command from the console mounted button, [it] gives a signal to the electric motors (one for each rear disc or as an alternate, one motor for both rear discs). The motors then apply the brake force via the calipers on the discs."

Since the EPB applies the brake force via calipers on the discs, it is of a friction type. In a conversation with Mr. Dion Casey of this office, you stated that although the EPB is actuated by

electrical means, it is retained by mechanical means. Additional information you submitted by fax on March 16, 2001, provided more details on the two design approaches under consideration. In that fax, you stated, "In the case of a non-reversible mechanism, the self-braking work gear itself guarantees the engagement of the parking brake. In the case of the reversible mechanism, it would be necessary to use a ratchet gear to lock the electric motor." It appears, therefore, that the EPB is "a parking brake system of a friction type with solely mechanical means to retain engagement," and would be permitted under the provisions of paragraph S5.2 of Standard No. 135.

In response to an analogous interpretation request from General Motors Corporation, we agreed that S5.2 of Standard No. 105 permits the parking brake to be applied and released by electrical or other non-mechanical means so long as the engagement is held by solely mechanical means. We interpret S5.2 of Standard No. 135 similarly.

I hope this answers your question. If you have any further questions regarding this matter, please contact Mr. Dion Casey at (202) 366-2992.

Sincerely,

John Womack
Acting Chief Counsel
ref:135
d.4/19/01