Interpretation ID: 77-3.4

TYPE: INTERPRETATION-NHTSA

DATE: 06/16/77

FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA

TO: J. R. Green

TITLE: FMVSS INTERPRETATION

TEXT: Your letter of April 8, 1977, to the President of the United States concerning the need for improved motor vehicle headlamp standards has been referred to this office for consideration and reply.

We have received considerable information regarding the effects of foreign and domestic motor vehicle headlighting equipment, including engineering papers and test data on "selective yellow" headlamps. All information concluded that filtering of headlamps to produce yellow reduces the photometric intensity of the lamp, thereby reducing the actual seeing distance. Some vehicle operators subjectively concluded they can see further with yellow headlamps, but objective seeing distance tests with specific target characteristics and distances indicate a loss of seeing distance.

It is also true that while the original intent in using yellow headlamps was to reduce the glare from oncoming vehicle headlamps, our current test data indicates that a yellow light does not reduce glare. The white light is, therefore considered safer and is the basis for requiring white light in Federal Motor Vehicle Safety Standard No. 108 (copy enclosed).

Although this lighting standard is generally in accordance with standards developed and published by the Society of Automotive Engineers, it does not specifically require sealed-beam headlamps. However, it does require headlamps which are designed to be aimed properly when installed in prealigned mechanical assemblies. The lamp itself may be sealed-beam (filament is enclosed only by the lamp shell in an inert atmosphere) or it may be a halogen lamp (filament is surrounded by a small envelope containing a halogen gas). Specifically, the halogen-bulb headlamp is legal if incorporated into an otherwise legal motor vehicle headlamp.

I trust the foregoing is fully responsive to your inquiry.

Sincerely,

ATTACH.

AUGUST 18, 1977

James R. Green 3396 Alma Street Lynwood, California 90262

Dear Mr. Green:

In his letter of June 16, 1977, our Mr. Driver, Director of the Office of Crash Avoidance, commented that although the Federal motor vehicle lighting standard "is generally in accordance with standards developed and published by the Society of Automotive Engineers, it does not specifically require sealed-beam headlamps."

This should not be interpreted as an opinion that Federal Motor Vehicle Safety Standard No. 108 does not require sealed beam headlamps. While there is no such requirement per se in the text of the standard, Standard No. 108 incorporates by reference SAE Standard J579a Sealed Beam Headlamp Units for Motor Vehicles, August 1965, and SAE Standard J580a Sealed Beam Headlamp, June 1966. Compliance of headlamps with these standards is required, whether as original or replacement equipment.

Sincerely, Joseph J. Levin -- Chief Counsel, NHTSA