Interpretation ID: nht74-1.5

DATE: 09/19/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: U. S. Technical Research Corporation

TITLE: FMVSS INTERPRETATION

TEXT:

NOA-30 (ZTV) Sep 19 1974

Mr. Bernard Belier U.S. Resident Engineer for Citroen, S.A. U.S. Technical Research Corporation 801 Second Avenue New York, New York 10017

Dear Mr. Belier:

This is in further reply to the petition of November 16, 1973, by Citroen, S. A. for rulemaking to amend Motor Vehicle Safety Standard No. 105-75, Hydraulic Brake Systems.

The petition has been thoroughly reviewed by engineering and legal staff personnel of this agency. Before a recommendation is made to the Administrator on the merits of your petition, we request that you furnish further information to us.

First of all, NHTSA is interested in obtaining any available data which will support the contention that the Citroen central power braking system provides a level of safety equivalent to a fully split system with indefinite residual failure mode performance such as is currently required by FMVSS 105-75. Do the highway accident statistics provide such support? Is the incidence of accidents occurring to Citroen vehicles attributable in whole or part to brake failures significantly different from the norm for other European passenger cars? Can it be demonstrated that when failures of the service brakes do occur in emergency situations, drivers are able to adjust their behavior patterns sufficiently quicly to bring the vehicles to a safe stop using the hand operated emergency brakes?

We wuld also like Citroen to provide data to substantiate that the "emergency" system can meet the deceleration requirement of 10 fpsps. What are Citroen's views on an appropriate burnish procedure for testing the emergency braking system? In addition to this, can the 10 fpsps deceleration requirement be achieved using the service brakes with a subsystem accumulator depleted?

Finally, we request data on the costs and leadtime required for Citroen to convert the single central power system to a dual, or full split system.

Yours truly,

Richard B. Dyson Acting Chief Counsel

cc: Maurice Clavel Assistant to the President S.A. Automobiles Citroen