Interpretation ID: nht91-6.15

DATE: October 7, 1991

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: Jon Nisper -- K.B. Lighting, Inc.

TITLE: None

ATTACHMT: Attached to letter dated 8-23-91 from Jon Nisper to Jerry Medelin (OCC 6403)

TEXT:

This responds to your FAX of August 23, 1991, to Jere Medlin of this agency. You have enclosed a drawing of a combination headlamp/turn signal lamp assembly that depicts two possible positions ("Case l," "Case 2") for the inboard wall. With respect to each, you have asked "where should the 100mm separation be measured for turn signal headlamp position?"

Let me begin by noting that there is no requirement in Standard No. 108 that front turn signal lamps be separated from headlamps by at least 100mm. However, if there is less than a 100mm separation of those lamps, S5.3.1.7 of Standard No. 108 provides that the multiplier applied to obtain the required minimum luminous intensities for the lamps shall be 2.5. NHTSA determines the distance of the separation pursuant to the provisions of paragraph 5.1.5.4.2 of SAE Standard J588 NOV84, "Turn Signal Lamps for Use on Motor Vehicles Less Than 2032 mm in Overall Width." That paragraph provides the following means of measuring spacing:

"Spacing for a front turn signal lamp which primarily employs a reflector (for example, one of parabolic section) in conjunction with a lens to meet photometric requirements, shall be measured from the geomeric centroid of the front turn signal functional lighted area to the lighted edge of the low beam headlamp or any additional lamp used to supplement or used in lieu of the lower beam, such as an auxiliary low beam or fog lamp."

We would apply this as follows. You stated in your letter that the inboard walls in your proposed headlamp/turn signal assembly serve no functional purpose. We interpret this as meaning that neither the inboard wall in Case 1 or Case 2 shown in your drawing would be used optically in the headlamp. Under this assumption, and the assumption that no direct light from the bulb filament illuminates the outer edges of the headlamp lens nearest the turn signal, the lighted edge of the headlamp reflector would end where the relevant inboard wall meets the reflector. Pursuant to SAE Standard J588 NOV 84, one would then take a vertical plane that is parallel to the axis of the headlamp bulb, and project it from the end of the lighted edge of the reflector (i.e., where the respective inboard wall meets the reflector) onto the lens. You have already drawn this as a line in the drawing enclosed with your FAX. Next, take the axis of the turn signal bulb and project it onto the lens (this line also exists in your enclosed drawing). To determine the separation, one would then measure the distance between the projected points on each lens. Should the headlamp lens area between the turn signal and the projected vertical wall line onto the headlamp lens be lighted, either on purpose or inadvertently, then the actual lighted edge of the headlamp would be used for measurement purposes.