Interpretation ID: nht78-3.14

DATE: 04/13/78

FROM: AUTHOR UNAVAILABLE; J. J. Levin, Jr.; NHTSA

TO: P. Arquin

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your recent letter asking what loading conditions are applicable for purposes of measuring the wheelbase of passenger cars, under the new phased-in passive requirements of Standard No. 208, Occupant Crash Protection. Apparently, the wheelbase of one of Peugeot's vehicles having an independent rear suspension varies as a function of the vehicle loading.

The phased-in passive requirements of Standard No. 208 were based on a determination of the lead time necessary to engineer passive restraints into each size class of automobile. Wheelbase was chosen as a measure to delineate the phasing requirements because it is directly related to vehicle size and because it is a well-defined quantity that does not vary significantly within a given car line.

For purposes of measuring wheelbase, the vehicle is loaded according to the general test conditions of Standard No. 208. These test specifications, including loading, are meant to approximate the likely condition of the vehicle under normal driving circumstances. Since a vehicle having a variable wheelbase will generally carry the same weight as the average automobile of its size, it is appropriate that the wheelbase on such a vehicle be determined under the loading conditions specified under Standard No. 208. Therefore, Peugeot should measure the wheelbase of its vehicle under the loading conditions specified in paragraph S8.1.1(a) of the standard.

SINCERELY,

U.S. TECHNICAL RESEARCH COMPANY

February 8th, 1978

Joseph J. Levin Chief Counsel National Highway Traffic Safety Administration U.S. Department of Transportation

Re.: Wheelbase Cutoff Points for FMVSS-208 Application

Dear Mr. Levin:

Certain automobiles with independent rear suspensions have a wheelbase which varies as a function of the vehicle loading. In order to determine the effective date of FMVSS-208 for one of our vehicles, it is necessary for us to know under which loading conditions the wheelbase should be measured. "Curb Weight" as defined in CFR 49, Chapter V, Subchapter A, Part 571, Subpart A, R 571-2 and "Unloaded Vehicle Weight" as defined in 36 F.R. 2511 (Feb. 5, 1971) have been suggested by your staff as the most probable possibilities

We would appreciate receiving a prompt official clarification on this matter.

P. Arquin Government and Engineering Liaison