Interpretation ID: nht92-1.1

DATE: December 30, 1992

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: T. Kouchi -- Director & General Manager, Automotive Equipment, Development & Administration Dept., Stanley Electric Co., Ltd.

TITLE: None

ATTACHMT: Attached to letter dated 11/23/92 from T. Kouchi to Paul J. Rice (OCC 8081)

TEXT:

This responds to your letter of November 25, 1992, asking for an interpretation of Motor Vehicle Safety Standard No. 108 as it relates to light-emitting diodes (LEDs).

You ask that we reply to the following three questions:

"(1) Is it possible for us to group LED tail & stop lamps into three categories in terms of the number of lighted sections to determine applicable photometric requirements, as specified in paragraph 4.1.5.1 of SAE J1889 DEC 88?"

The term "three categories" does not appear in Standard No. 108. Further, SAE J1889 is not incorporated into Standard No. 108, either by direct or indirect reference. We believe that you must be asking whether multiple light source lamps (such as LEDs) may be considered as lamps with three lighted sections for purposes of determining photometric compliance with Standard No. 108. The answer is yes, they may be so considered. We are aware that, in general, the use of LEDs does not permit distinguishing distinct lighted sections. As the agency explained to Valeo of France on July 7, 1992, because the SAE does not prescribe photometric requirements for more than three lighted sections in its materials that are incorporated into Standard No. 108, any device that contains more than three lighted sections, or LEDs, need only comply with the requirements prescribed for three lighted sections.

"(2) Where the above view is acceptable, could we consider the number of lighted section (sic) as 'one' in case of a lamp which contains three LED arrays arranged as shown in the attached drawing, if the circumferenc (sic) of three projected luminous areas does not exceed 150mm both in horizontal and vertical dimension?"

The answer is no under Standard No. 108 as it presently exists. The drawing you have enclosed depicts three "lighted areas of LEDs" with two separations. Your question is based upon SAE J1889, which defines a "one compartment LED lamp" as one whose "maximum projected linear dimension" does not exceed 150mm. Thus, the linear dimension of a two-compartment LED lamp is 151-300mm, and that of a three-compartment LED lamp is 301mm and greater. These dimensional specifications prevent LED lamps from achieving intensities higher than conventional filament lamps of similar sizes. However, we cannot base our answer upon SAE J1889 since it is not incorporated into Standard No. 108. Based upon our interpretation to Valeo, each of the lighted areas would constitute a three-section device because it contains three or more LEDs.

This, of course, could result in a lamp consisting of these three devices

creating glare in the eyes of a following driver, an undesirable result, and we believe that you should keep this possibility in mind in further development of this design.

"(3) Where the number of lighted section (sic) is determined as 'one' in the above, can we locate 'the geometric center of the illuminated area' at the point marked in the attached drawing, according to paragraph 2.6 of SAE J1889 JUN88?"

The answer is no because SAE J1889 is not incorporated into Standard No. 108. You must refer to the SAE requirements that are incorporated into Standard No. 108 that apply to the respective rear lamp functions in order to answer this question. These are SAE J588 NOV 84 and SAE J1385 APR 85 for turn signal lamps, SAE J586 FEB 84 and SAE J1398 MAY 85 for stop lamps, and SAE J585e September 1977 for taillamps.