Interpretation ID: nht93-6.39

DATE: September 20, 1993

FROM: Lawrence F. Henneberger -- Arent Fox Kintner Plotkin & Kahn

TO: John G. Womack -- Acting Chief Counsel, NHTSA

TITLE: Request for Interpretation

ATTACHMT: Attached to letter dated 1/25/94 from John Womack to Lawrence Henneberger (A42; Std. 105)

TEXT:

I am submitting this request for interpretation on behalf of my client, MICO, Incorporated (MICO), located in North Mankato, Minnesota, concerning the use of a brake lock supplementing the original equipment mechanical parking brake on a motor vehicle which in our opinion, (1) is not precluded by Federal Motor Vehicle Safety Standard (FMVSS) 105, and (2) does not otherwise impair braking operations in compliance with FMVSS 105. (1)

MICO believes that its brake lock will not cause noncompliance with or impairment of compliance with FMVSS 105 since: (a) the MICO brake lock is the type of auxiliary parking brake device which has consistently been determined by NHTSA not to raise compliance problems with respect to FMVSS 105; (b) based upon test results and in-service use of over 30 years, these brake locks have not had any adverse effect upon the hydraulic service brakes of the vehicle involved; (c) there have been no confirmed accidents attributable to the use of the brake locks for the 30 year period; and (d) the brake locks are installed after the vehicle manufacturer has certified the brake system of the vehicle with the requirements of FMVSS 105.

MICO recognizes that NHTSA does not give approvals of vehicles or equipment, and emphasizes that the Company is not here seeking any such approval. Rather MICO requests from the agency an interpretation that FMVSS 105 does not preclude the installation of a MICO hydraulic brake lock as a supplement to the systems installed to comply with the FMVSS 105 requirements.

BACKGROUND

MICO manufactures a hydraulic brake lock which supplements the mechanical parking brake of a motor vehicle by providing supplemental holding capacity for the vehicle. The brake lock is installed by a body builder or owner of a vehicle after the manufacturer of the vehicle has certified its compliance with applicable safety standards. The brake lock consists of a one-way check valve which, when it is in the release position, does not in any way impede or interfere with the use and application of the hydraulic service brakes on the vehicle. The brake lock is installed in the hydraulic brake lines between the master brake cylinder and the foundation brakes.

The brake lock does not render inoperative any device or element of the hydraulic service or parking brakes as originally installed on the motor vehicle but serves only to supplement the existing parking brake in a positive manner. The brake lock is not to be applied during normal driving operations but is only activated after the vehicle has been brought to a stop, the mechanical parking brake applied, and the brake lock armed. When the operator steps on the hydraulic service brake pedal and produces pressure in the brake system, the brake lock is activated. When activated, the brake lock acts as a

one-way check valve which will allow hydraulic system fluid to pass from the master cylinder to the foundation brakes as the brake pedal is applied, but will not allow the brake fluid to travel back to the master cylinder as the operator removes his foot from the brake pedal. (2) When the brake lock is not activated, brake fluid passes freely in both directions of the braking system. The brake lock does not increase brake pressure. It merely locks in pressure generated by applying pressure to the brake pedal when the vehicle is not in motion.

REGULATORY APPLICATION

In the case of a hydraulic brake lock, there is no safety standard which applies to it as a separate item of motor vehicle equipment. Previous interpretations of NHTSA have indicated that installation of a hydraulic brake lock does not affect compliance with FMVSS 105. See July 10, 1985 Letter of Interpretation from NHTSA Chief Counsel Jeffrey R. Miller to Mr. Bernard Cantleberry.

This position "is consistent with the agency's long-standing view about the (non-preclusive) use of auxiliary parking brake systems." See, e.g., May 6, 1993 Letter of Interpretation from Acting Chief Counsel John Womack to Mr. Bob Brinton (attaching a December 9, 1976 Interpretation from then Acting Chief Counsel Frank H. Berndt to Mr. Leon W. Steenbock); August 5, 1993 Letter of Interpretation from Acting Chief Counsel John Womack to Mr. Richard Muraski.

MICO submits that, in view of the fact that its brake lock demonstrably does not affect the operation of a vehicle's hydraulic brake system and, as long term usage has shown, has had no adverse effect upon the vehicle's hydraulic brake system, the vehicle will not be rendered noncompliant with FMVSS 105 upon the installation of the MICO brake lock.

TEST RESULTS

MICO has performed systematic and continuous testing of its hydraulic brake lock product to determine its effect on the performance of vehicles. MICO has conducted tests on the product in its own facilities under a number of different vehicle applications since the product was introduced in approximately 1960. The results of these tests show that the MICO brake lock does not adversely affect the continued satisfactory and compliant operation of the hydraulic brake system with FMVSS 105.

In addition, MICO also commissioned Bendix Corporation to conduct repetitive cycle tests of the product on a vehicle chassis in 1976, and these test results indicated that the brake lock is not detrimental to the continued satisfactory operation of the brake system. A copy of the May 1976 Bendix test evaluation is attached hereto as Appendix 2.

Several fleets have used and monitored the operation of these brake locks over substantial periods of time. MICO brake locks have operated for these fleets on a trouble-free basis on vehicles which travel between 25,000 to 40,000 miles per year. See, Report on Use of MICO Brake Locks, supra, at 3-4 and attached surveys. The locks have not caused any brake failure of any brake system component and there have been no accidents attributable to the use of the MICO brake lock. The results of this in-service experience have confirmed that the

MICO brake locks do not adversely affect the performance of the original hydraulic service brakes and associated parking brake systems in normal operation with the MICO brake lock released.

Based upon the test and usage data, MICO believes that the addition of the brake lock to a motor vehicle will not affect the vehicle's compliance with FMVSS 105.

CONCLUSION

For the reasons set forth above, MICO, Inc. respectfully requests an interpretation confirming its view that the addition of a MICO brake lock to a motor vehicle is not precluded by FMVSS 105, and does not impair braking performance in compliance with FMVSS 105.

We appreciate your consideration of our request for interpretation and encourage you to contact the undersigned should questions remain.

1 Copies of MICO's brake lock product catalogs, including materials relating to its newest product, the MICO 690 Series, were provided to representatives of your staff and the Crash Avoidance Division on August 17, 1993.

2 For a detailed discussion of the description, application and usage of MICO brake lock products, see Report on Use of MICO Brake Locks by Messrs. Hall and Vogel (June 29, 1993), attached hereto as Appendix 1.