Interpretation ID: nht92-7.4

DATE: May 14, 1992

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: Al Twyford

TITLE: None

ATTACHMT: Attached to letter dated 4/21/92 from Al Twyford to Associate Administrator for Safety, Federal Highway Administration (OCC 7244)

TEXT:

This responds to your letter of April 21, 1992, to the Federal Highway Administration, which has been forwarded to this agency for reply.

You wish to complain "about some makes of new cars that have two sets of headlights (4) which operate at the same time." If this agency plans to do nothing about it, you "plan to take this matter up with Congressmen and U.S. Senators."

You are not alone in your concern about headlamp glare created by new motor vehicles. Other citizens have brought the subject to the attention of Members of Congress. I enclose a copy of a recent letter from the Deputy Administrator of this agency to Senator Cohen of Maine which is representative of our views on this issue. You will see that a number of factors may be responsible for creating a perception of glare. We note that you have already been in touch with the Department of California Highway Patrol, and that California has no periodic motor vehicle inspection.

With respect to the specific comments in your letter, the agency does not "approve" specific headlamp designs. Standard No. 108 sets forth photometric performance requirements to be met on both the upper and lower beam, and does establish maximum limitations at some of the photometric test points. Further, in a four-headlamp system, the upper and lower beams may be provided by all headlamps. Headlamp manufacturers must ensure that their products meet these requirements, and certify that each headlamp complies by placing a "DOT" mark on the lamp. There is no requirement that a manufacturer obtain permission from this agency before introducing the lamps into the market.

We appreciate your concern.

Enclosure

April 16, 1992

The Honorable William S. Cohen United State Senate Washington, DC 20510-1901

Dear Senator Cohen:

Thank you for your letter requesting information on the quality of automobile headlamps. Our information should help you respond to a letter from Mr.

Lowell Spicer, of Brunswick, Maine, who wrote you about headlamp glare and other issues.

The National Highway Traffic Safety Administration is authorized by the National Traffic and Motor Vehicle Safety Act to issue safety standards for new motor vehicles and items of motor vehicle equipment. Under that authority, the National Highway Traffic Safety Administration has issued vehicle safety standards on a wide variety of subjects. One of these standards, Federal Motor Vehicle Safety Standard (FMVSS) No. 108, "Lamps, Reflective Devices and Associated Equipment," addresses the safety requirements for vehicle headlighting.

Two of FMVSS No. 108's requirements standardize the beam pattern and light intensity of headlamps. All new headlamps must meet these requirements, which have remained essentially unchanged since 1978. Halogen headlamps may appear much brighter, but they meet the same minimum and maximum output requirements as normal incandescent headlamps. They appear much brighter because of the color spectrum of their light, i.e., they emit light which appears whiter than the light emitted by incandescent headlamp. Another of FMVSS No. 108's requirements allows headlamps to be installed or "mounted" in a proper ground clearance and ramp angles for heavy duty and other vehicles. Because of their size and other characteristics, trucks often have headlamps that are mounted higher than other vehicles.

Our headlamp compliance tests for beam pattern and light intensity show, that when properly aimed, recent model-year headlamps generally fall well within the limits established for glare brightness. However, our tests do not account for the effect of different mounting heights or misaiming. Headlamp replacement and vehicle loading can alter headlamp aim and are often the cause of glare complaints.

Another aspect of recent model-year vehicles that could be contributing to glare is the improper use, misaiming or improper installation of auxiliary fog or driving lamps. These are regulated solely by state law.

The agency has found that factors such as reduced night vision capabilities as people age can adversely influence driving performance. Headlamp glare resistance reduces with driver age. According to research, the headlamp glare resistance of the human eye at age 20 is twice as good as it is for the age of 72. Contrast sensitivity is also an important factor in night vision, and it reduces dramatically, requiring more illumination to see objects as drivers age.

Concerning vehicle headlamps and their brightness due to misaim, States regulate headlamp aim in motor vehicle use and inspection laws. Maine has an annual motor vehicle inspection law. Should Mr. Spicer want to contact his State on the matter of headlamp aim inspection he should contact the following:

Administration of Laws Mr. G. William Diamond, Secretary of State Department of Secretary of State Nash School Station, #148 Augusta, ME 04333

Enforcement of Laws Mr. John Atwood, Commissioner

Department of Public Safety 336 Hospital Street Augusta, ME 04333.

I hope that we have provided enough information to help you answer Mr. Spicer's concerns.

Sincerely,

Frederick H. Grubbe