Interpretation ID: nht67-1.31

DATE: 09/21/67

FROM: AUTHOR UNAVAILABLE; SIGNATURE UNAVAILABLE; NHTSA

TO: Busby and Rivkin

TITLE: FMVSS INTERPRETATION

TEXT: In your letter of July 13, 1967, you requested clarification of several issues relating to the location and size of turn signals as specified in the Initial Federal Motor Vehicle Safety Standards.

Initial Standard No. 108, entitled, "Lamps, Reflective Devices, and Associated Equipment - Multipurpose Passenger Vehicles, Trucks, Trailers, and Buses, 80 or More Inches Wide Overall," specifies that turn signal lamps shall conform to Class A of SAE Standard J588d. As stated in the enclosures to your letter, SAE Standard J588d specifies that the optical axis (filament center) of the front turn signal lamp shall be at least 4 inches from the inside diameter of the retaining ring of the headlamp unit providing the lower beam. This requirement of the SAE Standard is addressed to a single lamp with only one bulb. For a combination of lamps, such as that shown on the sketch enclosed with your letter, the intent of this requirement could be part if the optical center produced by the two bulbs is outside the 4-inch limit. The location of this optical center must be determined from laboratory test data, which was not presented in your letter.

Proposed Initial Standard No. 112, entitled, "Lamps, Reflective Devices, and Associated Equipment - Passenger Cars; Motorcycles; and Multipurpose Passenger Vehicles, Trucks, Trailers and Buses of Less than 80 Inches Wide Overall," would permit the use of Class A (SAE J588d) turn signal lamps until January 1, 1969. Under this provision, lamp No. 1 on your sketch would conform to the 4-inch spacing requirement. Combining lamp No. 1 and No. 2 to obtain a Class A area would again result in the situation previously described with respect to location of the optical center.

Since your letter makes frequent reference to "cars," we assume that you are primarily interested in the requirements of Standard No. 112. In this respect, we would caution you that the requirements specifies therein are presently only proposed requirements, and are subject to change prior to issuance of the final standard.

Thank you for your interest in the motor vehicle safety standards.