Interpretation ID: nht75-1.7
DATE: 02/07/75
FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA
TO: Nissan Motor Co., Ltd.
TITLE: FMVSS INTERPRETATION
TEXT:
N40-30 FEB 7 1975
Mr. Tatsuo Kato Staff, Safety Nissan Motor Co., Ltd. P. O. Box 1606 Englewood Cliffs, New Jersey 07632
Dear Mr. Kato:
This responds to your December 18, 1974, question whether the test procedure in S7.11.2.1 of Standard No. 105-75, Hydraulic brake systems, that specifies "Accelerate immediately... after each stop" can be interpreted to permit a maximum rate of acceleration to the initial test speed of 60 mph. You also ask whether, in the case of a vehicle incapable of attaining 60 mph, the S5.1 requirement that it be tested "at the highest speed attainable in the time or distance interval specified" can also be interpreted to permit a maximum rate of acceleration.
Both of these specifications permit acceleration at maximum speed. As in the case of any performance requirement, when a test procedure is not specified, a manufacturer must only "exercise due care" to assure himself that each of his vehicles meets the requirements, by selecting a reasonable test procedure to demonstrate compliance. In fact the NHTSA has consistently stated that, even when a test procedure is stated, a manufacturer may use a different procedure, so long as it is calculated, in the exercise of due care, to demonstrate that the vehicle would comply if tested in accordance with the procedure.
Because the NHTSA has chosen not to specify an acceleration rate in S7.11.2.1 for fade tests, the manufacturer may reasonably choose the maximum or near maximum acceleration rate which ensures the greatest cooling effect in the brake assembly. This interpretation is also true for vehicles which are unable to attain 60 mph and must therefore reach their "highest speed" under S5.1 prior to braking.
Therefore, in both cases cited, you may interpret the procedures to permit acceleration at "maximum rate" as specified in S7.11.3.1.
Yours truly,
Richard B. Dyson Acting Chief Counsel