Interpretation ID: nht93-4.11

DATE: May 28, 1993

FROM: John Womack -- Acting Chief Counsel, U.S. Department of Transportation, NHTSA

TO: Thomas Luckemeyer -- SWF Auto-Electric Guild GmbH

TITLE: None

ATTACHMT: Attached to letter dated 4-28-93 from Thomas Luckemeyer to Taylor Vinson (OCC 8589)

TEXT: As you have requested, we are responding by FAX to your letter of April 28, 1993, to Taylor Vinson of this Office. You have asked two questions with respect to the acceptability of a multiple rear turn signal lamp under Federal Motor Vehicle Safety Standard No. 108, and have enclosed a sketch of the lamp.

Your first question is:

"Is it allowed to split the turn signal lamp in two parts with the dimensions given in the sketch . . . where the bigger part (4.5 sq. in.) is on the body of the car. The distance does not exceed 22 in."

Your question indicates that the turn signal lamp array of two lamps that is illustrated in the sketch is intended for installation on passenger cars or other vehicles whose overall width is less than 80 inches. Standard No. 108 incorporates by reference the SAE standard applicable to such vehicles, J588 NOV84. Paragraph 5.1.5.2 of SAE J588 NOV84 permits the use of multiple rear turn signal lamps to meet the photometric requirements of Standard No. 108.

When multiple lamps are used to meet the photometric requirements of a rear turn signal lamp, paragraph 5.3.3 of SAE J588 NOV84 requires that the functional lighted lens area of each lamp shall be at least 22 sq. cm, provided the combined area is at least 37.5 sq. cm. Your sketch shows that the functional lighted lens area of one lamp is 23 sq. cm, and of the other, 30 sq. cm, with a combined area of 53 sq. cm. Therefore, Standard No. 108 permits you to use the turn signal lamp array shown in your sketch.

Your second question is:

"Is it allowed to use the combination of the two lamps to meet the photometric requirements."

Because the distance between the two adjacent light sources in the array does not exceed 560 mm (the sketch indicates that it is less than 550 mm), paragraph 5.1.5.2 of SAE J588 NOV84 requires that the combination of the lamps be used to meet the photometric requirements for the corresponding number of lighted sections, two in this case.