Mr. Guy Dorleans

International & Regulatory Affairs

Valeo Lighting Systems

34, rue Saint-Andr

93 012 Bobigny Cedex


Dear Mr. Dorleans:

This responds to your letter, in which you ask about the activation of daytime running lamps (DRLs) under Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment. Specifically, you ask whether various LED (light-emitting diode) lamp designs, incorporating a parking lamp function in addition to other functions, can be used as DRLs under the standard. Our answer is that this would not be prohibited by FMVSS No. 108.

By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approvals of motor vehicles or motor vehicle equipment.  Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture. NHTSA selects a sampling of new vehicles and equipment each year to determine their compliance with applicable FMVSSs.  If our testing or examination reveals an apparent noncompliance, we may require the manufacturer to remedy the noncompliance, and may initiate an enforcement proceeding if necessary to ensure that the manufacturer takes appropriate action.

The relevant language in FMVSS No. 108 regarding the regulation of DRLs is paragraph S5.5.11(a). This paragraph reads, in part:

Any pair of lamps on the front of a passenger car, multipurpose passenger vehicle, truck, or bus, whether or not required by this standard, other than parking lamps or fog lamps, may be wired to be automatically activated, as determined by the manufacturer of the vehicle, in a steady burning state as daytime running lamps (DRLs) and to be automatically deactivated when the headlamp control is in any on position

In your letter, you described two scenarios in which an array of four LEDs that could serve as both a parking lamp and as a DRL. In the first scenario, one LED in the array is activated alone in parking lamp mode, while all four are activated in DRL mode. In the second scenario, all four LEDs in the array are activated at a low intensity in parking lamp mode, and all four are activated at a higher intensity in DRL mode. You indicated that for both scenarios the lamp would meet the specified photometric requirements for whichever function was activated, i.e., parking lamp or DRL. We believe that both designs would be permitted by FMVSS No. 108.

In a 1997 letter of interpretation which we have enclosed,[1] we explained the rationale of prohibiting parking lamps to be used as DRLs. In that letter, we stated:

[A] manufacturer may use any pair of front lamps for the DRL feature, other than parking lamps (too small to be effective) or fog lamps (too bright).

For the purpose of S5.5.11(a), the array of LEDs that you described in your letter, which can serve the function of parking lamps or other lamps depending on how they are activated, would not be considered parking lamps in either of the scenarios that you described. In DRL mode, the lamps would be substantially brighter than the parking lamps, and according to your letter, their photometric output would comply with the requirements of S5.5.11(a)(1), which sets minimum and maximum output for DRLs. This would result in effective DRLs, which is the intent of the requirement in FMVSS No. 108.

We also note that the use of multifunction lamps, including lamps that function, in part, as parking lamps, were considered in the development of the DRL standards. In a 1988 letter of interpretation,[2] we stated that:

[A] lamp that functions both as a parking lamp and a DRL and which is operated in daylight could act as either a DRL or a parking lamp, depending on the intensity of the light emitted, but it would have to meet the photometric requirements for the function being exercised.

If you have any further questions, please contact Ari Scott of my staff at (202) 366-2992.

Sincerely yours,

Anthony M. Cooke

Chief Counsel




[1] September 29, 1997 letter to Mr. Walter E. Ellis, available at

[2] February 19, 1988 letter to Mr. M. Arisaka, available at This statement was analyzing the proposed language in FMVSS No. 108, later adopted, requiring that a DRL would have to be a lamp other than a parking lamp. [emphasis added]