Interpretation ID: nht92-7.21

DATE: April 30, 1992

FROM: Timothy C. Murphy -- Chairman, TSEI Engineering Committee (Lights), Transportation Safety Equipment Institute

TO: Paul Jackson Rice -- Chief Counsel, NHTSA

TITLE: Re: Request for Interpretation

ATTACHMT: Attached to letter dated 5/27/92 from Paul J. Rice to Timothy C. Murphy (A39; Std. 108)

TEXT:

In adopting the definition of "effective projected luminous lens area," NHTSA declined to adopt the SAE language dealing with lens parts, "even if they do not contribute significantly to the total light output." The agency went on to state, "(t)o be fully effective the lamp must project light in an appropriate manner. (Federal Register, p. 50182-4 Vol. 55, No. 234/Dec. 5, 1990).

On behalf of the Transportation Safety Equipment Institute (TSEI)* I would like to obtain an interpretation whether the lens leg of various lamp assemblies may be included in the calculation of 75 square centimeters or 11.625 square inches.

Figure 1 attached graphically shows that the last optic against the lens leg projects light outward beyond the lens leg and yet the light may be beneficial to meeting the twenty degree outward test points for stop, tail, turn lamps. Therefore I would conclude that this light, although low in intensity due to its distance from the filament, may be significant as far as meeting the photometric requirements of the lamp.

I request a ruling from NHTSA on how the agency would interpret the use of lens rims or legs to fulfill the 75 square centimeters requirements.

* TSEI is a non-profit trade association, representing North American manufacturers of vehicle safety equipment, including headlighting and signal lighting products, rearview mirrors, reflex reflectors, emergency lighting and other safety equipment for emergency, service and related vehicles and emergency warning triangles.

Attachment Figure 1 omitted.