Mr. Bernard Caire
DBM Reflex Enterprises, Inc.
1620 boul. Dagenais ouest
Laval, Quebec H7L 5C7

Dear Mr. Caire:

This is in reply to your FAX of January 25, 1996, to Taylor Vinson of this Office, asking for two interpretations of paragraph S5.3.1.7 of Motor Vehicle Safety Standard No. 108 as they relate to your specific lighting array, for which you enclosed two drawings. These depict a housing containing a "turn signal" and a "daytime running light." You clarified your request in a telephone conversation with Rich VanIderstine of this agency on February 23, 1996.

Paragraph S5.3.1.7 modifies luminous intensity requirements for turn signal lamps "on a motor vehicle on which the front turn signal lamp is less than 100mm from the lighted edge of a lower beam headlamp, as measured from the optical center of the turn signal lamp." You ask, with respect to each of your drawings, whether the optical center of the turn signal is the same as the filament position. You note that there will be a higher light intensity in front of the bulb location.

Your first question appears to relate to turn signal/headlamp spacing, but we believe that your true concern is with the spacing relationship between a turn signal and a daytime running lamp (DRL). Because your DRL is a dedicated lamp serving only the DRL function, paragraph S5.3.1.7 does not apply.

The correct reference regarding the spacing between DRLs and turn signal lamps is paragraph S5.5.11(a)(4). This, in pertinent part, places the DRL "so that the distance from its lighted edge to the optical center of the nearest turn signal

lamp is not less than 100 mm . . . ." To determine the optical center of the turn signal lamp, we must refer for an answer to SAE J588 NOV84 Turn Signal Lamps For Use on Motor Vehicles Less Than 2032 MM in Overall Width. The answer depends on the design of the turn signal lamp. If the lamp primarily employs a reflector (for example, one of parabolic section) in conjunction with a lens, spacing is measured from the geometric centroid of the front turn signal functional lighted area to the lighted edge of the lower beam headlamp (paragraph, SAE J588 NOV84). The "geometric centroid" is the "optical center" for purposes of Standard No. 108. If the front turn signal is a direct light source type design, that is a lamp primarily employing a lens and not a reflector to meet photometric requirements, spacing is measured from the light source to the lighted edge of the DRL. The filament center of the light source is the "optical center" for purposes of Standard No. 108. If the distance is less than 100 mm, the requirements of S5.3.1.7 apply and the minimum intensity of the turn signal must be at least 2.5 times that normally required.

If you have any further questions, you may call Taylor Vinson of this office (202-366-5263).


Samuel J. Dubbin Chief Counsel ref:108 d:3/14/96