Interpretation ID: nht90-3.72

TYPE: Interpretation-NHTSA

DATE: August 30, 1990

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: Richard E. Portors -- Vice President and General Manager, Royale Limousine Manufacturers

TITLE: None

ATTACHMT: Attached to letter dated 4-5-90 from R.E. Portors to Z.R. Fraser; Also attached to Federal Register, section 571.108, 49 CFR Ch.V (10-1-85 Edition), page 218 (text omitted)

TEXT:

This is in reply to your FAX of April 5, 1990, to Zachary R. Fraser of this agency's Office of Vehicle Safety Compliance, requesting confirmation of your interpretation of a requirement applicable to center highmounted stop lamps. You attached a copy of the requirements for our convenience.

Section S5.1.1.41(a) of Standard No. 108 (S4.1.1.41(a) in your copy) requires the center lamp to have an effective projected luminous area of not less than 4 1/2 square inches. You report that the lamp on the 1990 Cadillac measures 6 square inches in ar ea. When a boomerang TV antenna is installed, the shaft area displaces 1.125 square inches of area which would leave an exposed area of 4 7/8" of light and would exceed the minimum requirements of section (a)." You further state that subsection (b) (re lating to visibility of signal throughout the horizontal angle from 45 degrees right to left of the longitudinal axis of the vehicle) would not be affected. Further, "without window glazing", section (c) relating to compliance with the photometrics of F igure 10, would not be affected either, in your opinion.

First, we note that your interpretation of subsection (a) is not correct. The effective projected luminous lens area of the lamp remains at 6 square inches, because no modifications are performed on the lamp that affect the lens itself. The question for compliance is whether the photometric requirements of subsection (c) are met. We do not understand your phrase "without window glazing", as compliance is determined with the back window in place. However, in our experience, a TV boomerang antenna is, like the lamp, mounted on the vertical centerline of the vehicle, usually the rear deck. In this position, even a shaft that displaces 1.125 square inch of area will block the light from the lamp at test point H-V, and the lamp will not comply with the photometric requirements of "Figher 10, as specified by subsection (c). Therefore, we cannot concur in your interpretation that the design you describe "would not affect the requirements of 571.108."