Interpretation ID: nht92-1.12

DATE: 12/24/92

FROM: PAUL JACKSON RICE -- CHIEF COUNSEL, NHTSA

TO: KENNETH W. WEBSTER II -- PROJECT ENGINEER, TRANSPORTATION RESEARCH CENTER INC.

ATTACHMT: ATTACHED TO LETTER DATED 10-26-92 FROM KENNETH W. WEBSTER, II TO PAUL J. RICE (OCC 7930)

TEXT: This responds to your letter of October 26, 1992, seeking an interpretation of Standard No. 124, Accelerator Control Systems (49 CFR @ 571.124). More specifically, your letter requested clarification of the correct test procedure for S5 of Standard No. 124 under a specific condition.

By way of background information, under the National Traffic and Motor Vehicle Safety Act, each manufacturer is responsible for certifying that its vehicles or products meet all applicable safety standards. Manufacturers must have some basis for their certification that a vehicle or product complies with all applicable safety standards. This does not necessarily mean that a manufacturer must conduct the specific tests set forth in an applicable standard. Certifications may be based on, among other things, engineering analyses, actual testing, and computer simulations.

Section S5 of Standard No. 124 requires vehicles to comply with certain requirements "when the engine is running under any load condition, and at any ambient temperature between -40 degrees F. and +125 degrees F. after 12 hours of conditioning at any temperature within that range." (Emphasis added.) For purposes of the safety standards, the term any "means generally the totality of the items or values, any one of which may be selected by the Administration for testing." (49 CFR @ 571.4) Therefore, vehicles must meet Standard No. 124's requirements at all temperatures within the specified range.

Your letter states that some vehicles are impossible to start after conditioning for 12 hours at -40 degrees F. You asked which of the following procedures would be correct when testing a vehicle which will not start:

Alternative (1): Test with engine not running at the -40 degrees F. test condition.

Alternative (2): Raise temperature until engine will start. Record test temperature and perform test.

In conducting a compliance test, NHTSA would follow the procedures set forth in Standard No. 124. The agency would not follow the Alternative (1) test procedure since the standard specifies requirements that must be met "when the engine is running."

The agency could conduct a compliance test at any temperature or temperatures within the specified -40 degrees F. to +125 degrees F. range. I note that S5.3 specifies that the performance requirement for maximum time to return to idle position varies depending on whether the vehicle is "exposed to ambient air at 0 degree F to -40 degrees F. during the test or for any portion of the 12-hour conditioning period." This language makes it clear that the ambient air does not need to be held at a single temperature during the conditioning period or during the test.

If NHTSA chose to conduct a compliance test at -40 degrees F. and the vehicle would not start because of the extreme cold, the agency would most likely either use a standard engine heater to assist in starting the vehicle or warm the entire vehicle to a temperature where it would start. I note, however, that if the agency did warm the vehicle to assist in starting, it might lower the temperature back down to -40 degrees for purposes of conducting the test.

I hope you find this information helpful. If you have any other questions, please contact Mary Versailles of my staff at this address or by phone at (202) 366-2992.