Interpretation ID: nht78-2.11

DATE: 07/10/78

FROM: AUTHOR UNAVAILABLE; M. M. Finkelstein; NHTSA

TO: Hon. Paul Trible - H.O.R.

TITLE: FMVSS INTERPRETATION

TEXT: This is in response to the letter (enclosed) you received from your constituent Mr. Randy Churaman of Hampton, Virginia, concerning plexiglass covers for headlights.

The National Highway Traffic Safety Administration (NHTSA) in 1972 proposed rulemaking to allow fixed plastic covers over motor vehicle headlights. However, during the comment period of the proposed rule-making some controversial items that were raised regarding fixed plastic headlight covers initiated concerns with respect to motor vehicle safety. These concerns were that: (1) moisture condenses inside the plastic covers and greatly increases headlight glare to oncoming traffic, (2) the plastic covers get scratched, thus reducing headlight output and increasing headlight glare at the same time, (3) plastic headlight covers have to be removed to mechanically aim headlamps, which becomes quite expensive to the vehicle owner and (4) correct aim of headlights is often made incorrect when installing fixed plastic headlight covers. Finally, the change in air drag by use of plastic headlight covers is extremely small since the air drag is primarily related to the overall frontal area projection of the vehicle.

Because of the foregoing disadvantages, and no major advantage to fixed plastic headlight covers other than styling, Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices and Associated Equipment, prohibits fixed plastic covers over headlamps. Specifically, FMVSS No. 108 references SAE Standard J580a, which states in part . . . "When in use, a headlamp shall not have any styling ornament or other feature, such as a glass cover or grill, in front of the lens." There is, however, no prohibition on the installation of original equipment retractable clear plastic headlamp concealment devices on newly manufactured motor vehicles.

I trust the foregoing is fully responsive to your inquiry.

ENC. CONSTITUENT'S LETTER

EXECUTIVE TOWER, BOX 59 2101 EXECUTIVE DR. HAMPTON, VA 23666

Dear Mr. Trible

I own a Datsun 280 Z sports car which has a very aerodynamic front end except for the cutouts for the headlights (see sketch). In other countries there are clear plexiglass covers available for the headlights, which fit over the cutouts, and complete the aerodynamic lines. In this country these covers are illegal for reasons which are beyond my comprehension since they would reduce the air drag of the car, and therefore give better gas milage. I would like to see the law changed to permit the use of these headlight covers, or know why they are illegal.

Randy Churaman

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