Interpretation ID: nht88-3.93

TYPE: INTERPRETATION-NHTSA

DATE: 11/03/88 EST

FROM: ERIKA Z. JONES -- CHIEF COUNSEL, NHTSA

TO: A. L. BRAGG -- LABORATORY MANAGER, TRUCK-LITE CO., INC.

TITLE: NONE

ATTACHMT: LETTER DATED JUNE 22, 1988 RE: REQUEST FOR INTERPRETATION OF S4.1.1.16 AND S4.1.17 IN STANDARD NUMBER 108; OCC-2303

TEXT: This is in reply to your letter of June 22, 1988, to Mr. Vinson of this Office asking for an interpretation of Motor Vehicle Safety Standard No. 108.

It is your understanding that for purposes of measuring the effective projected illuminated area of a lens, the reflex area, if any, must be subtracted from the total lens area. Your company manufactures a combination lamp which "has four square inches of reflector area and eight square inches of stop, tail and turn area." You have asked if you may advise your customers that this lamp may be used on vehicles whose overall width is 80 inches or more:

"A) Singularly (that is one on each side of the vehicle in the rear) as a stop, turn, tail and reflex reflector?

B) In combination of two's or three's (on each side of the rear of the vehicle), provided that the lamps are separated by at least twenty-two inches?"

Your understanding is correct, that the effective projected illuminated lens area must be determined without reference to any reflex reflector that may be combined with it. If the turn signal function in your lamp is met by one compartment, your lamp is acceptable under "A)." But if the turn signal function is met by more than one compartment, your lamp would not be acceptable as the area of each compartment is less than 12 square inches. With regard to "B)," the lamps could be used in combinations of twos and threes if they are mounted more than 22 inches apart but could not be used if mounted closer than 22 inches.

You also asked about the relationship to paragraph S4.1.1.7. This paragraph covers replacement equipment only, without reference to its location on a vehicle. It applies only to turn signal lamps intended to replace original equipment turn signal lamps on vehicles manufactured in accordance with SAE Standard J588d, June 1966. The current original equipment is SAE standard J588e September 1970.

You should be aware that the Truck Safety Equipment Institute has petitioned for rulemaking the effect of which would be to extend the 12-inch requirement to lamps used on all wide vehicles without reference to the 22-inch spacing. At present the agency is reviewing this petition.

I hope that this answers your questions.