Interpretation ID: nht90-3.71

TYPE: Interpretation-NHTSA

DATE: August 30, 1990

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: S. Watanabe -- General Manager, Automotive Equipment Technical Coordination Dept., Stanley Electric Co., Ltd.

TITLE: None

ATTACHMT: Attached to letter dated 7-13-90 from S. Watanabe to S.P. Wood

TEXT:

This responds to your letter of July 13, 1990, requesting an interpretation of how the photometric requirements of FMVSS 108 would apply to a combined taillamp and side marker lamp. Your letter indicates that "the light output of side marker lamp is als o emanated toward the rear of the vehicle mixed with tail lamp light, and similarly, the light output of tail lamp is also emanated toward the side mixed with side marker lamp light." You requested answers to the following two questions.

"1) Should the Tail lamp function of this lamp meet the photometric requirements for 2 lighted sections, or 3 lighted sections?"

Although NHTSA and the SAE have not defined "lighted section", we understand it to be that portion of a lens that is illuminated, either singly by a single light source, or in common by more than one light source. Your question assumes that the number o f bulbs in your lamp is equal to the number of lighted sections, that is to say, that each bulb illuminates a separate section of the lens. However, in your design, all bulbs contribute, without interruption by a divider or other light-directing feature , to the illumination of the lens. Therefore, we regard your lamp as a single compartment lamp to which the single lighted section requirements of SAE Standard J585e Tail Lamps (Rear Position Lamps), September 1977, apply, even though the illumination i s provided by three light sources.

"2) Should the Side marker function of this lamp meet the photometric requirement of SAE J592e by 3 lighted sections or 1 lighted section?"

Standard No. 108 also incorporates by reference SAE Standard J592e Clearance, Side Marker, and Identification Lamps, July 1972. Unlike SAE J585e, SAE J592e does not contain different photometric requirements depending on the number of lighted sections. Therefore, we interpret your question as asking whether photometric compliance is determined on the basis of the bulb that is dedicated to that purpose, or by all three bulbs. Because there is no clearly defined side marker lamp other than the portion of the lamp that is visible from the side, compliance should be measured using all three light sources in the lamp.

I hope you find this information helpful.