Interpretation ID: 86-1.29

TYPE: INTERPRETATION-NHTSA

DATE: 02/10/86

FROM: AUTHOR UNAVAILABLE; Erika Z. Jones; NHTSA

TO: Mr. T. Chikada

TITLE: FMVSS INTERPRETATION

TEXT:

February 10, 1986 Mr. T. Chikada Manager, Automotive Lighting Engineering Control Dept. Stanley Electric Co., Ltd. 2-9-13, Nakameguro, Meguro-ku Tokyo 153, Japan Dear Mr. Chikada: This is in reply to your letter of November 13, 1985, to the former Chief Counsel of this agency, Jeffrey R. Miller, with respect to the ratio of the candlepower between the taillamp, stop lamp, and turn signal lamp (Federal Motor Vehicle Safety Standard No. 108). You have enclosed a hypothetical two-compartment lamp design which could be manufactured in three variations of stop, turn signal, and taillamp combinations (layout 1, layout 2, and layout 3). Standard No. 108 incorporates by reference various SAE standards which prescribe candlepower ratios for multiple compartment lamps (J585e Taillamps; J586c Stop Lamps; J588e Turn Signal Lamps). You ask how you can apply the ratio of the candlepower between the lamps. The requirements to which you refer are contained in Note 4 to Table 1 of each of the referenced SAE standards, which in turn cite paragraph 3.1 of each standard. The first sentence of Note 4 establishes the ratio when one function is combined with another (that is to say, optically combined within a single compartment). The second sentence of Note 4 provides, however, that if a multiple compartment lamp is used and the distance between the optical axis for both functions is within the dimensions specified in paragraph 3.1, the ratio is computed with all the compartments lighted. The third sentence of Note 4 states that if these dimensions are exceeded the ratio is computed for only those compartments where the functions are optically combined. In layout 1 the turn signal lamp is not combined with the tail/stop lamp and you have asked for confirmation that only the ratio between the tail lamp and stop lamp must be considered. That is correct. The dimension specified in paragraph 3.1 of each of the SAE standards is a maximum of 22 inches between filament centers in two-compartment lamps. Your layout 2 combines the tail lamp and turn signal lamp in one compartment, and the tail lamp and stop lamp in the second, whereas in layout 3 the first compartment contains one lamp, the tail lamp, and in the second compartment, the tail lamp, stop lamp, and turn signal lamp are present. You ask for confirmation that only the ratios of the lamps in the individual compartments shall be considered. Your hypothetical lamp design does not depict the distance between filament centers of each function, but if they exceed 22 inches then you are correct with respect to layouts 2 and 3. If the distance is less than 22 inches, then the ratio is computed with both compartments lighted. I hope that this answers your questions.

Sincerely, Original Signed By Erika Z. Jones Chief Counsel