U.S. News: NHTSA Interprets Lighting Standard Application

The U.S. National Highway Traffic Safety Administration (NHTSA) has issued a policy statement on how it will enforce the federal lighting standard, Federal Motor Vehicle Safety Standard (FMVSS) No. 108, with respect to replacement lighting equipment.
The policy statement completes action on two draft letters of interpretation issued last year that proposed to prohibit replacement items that did not conform to federal standards in the same manner as the original equipment and use the same light sources as the original equipment.
Aftermarket groups protested this restrictive interpretation, pointing out that the lighting standard establishes only performance requirements, not design stipulations. In its policy statement, NHTSA acknowledges that replacement equipment does not have to be identical to original equipment. Without establishing design specifications, NHTSA will require that replacement equipment must incorporate all required functions of the original equipment it is designed to replace.
However, the replacement equipment can eliminate features that are not required functions and it can add supplemental features that were not part of the original equipment. NHTSA will permit alternative light sources for replacement lighting equipment other than headlamps, provided that the replacement equipment meets FMVSS No. 108 (ex: it is permissible to replace an incandescent taillamp bulb with a red light-emitting diode).
Nevertheless, with respect to headlamps, NHTSA will proceed with its original interpretation that replacement headlamps must comply with all applicable photometry requirements using the same light sources as the OE equipment (ex: it is illegal to switch incandescent bulbs with high intensity discharge (HID) headlamps).
For lighting equipment other than headlamps, NHTSA intends to provide some flexibility in selling pairs of lamps in which the design configuration for an individual lamp is not identical to the original equipment but the lamp nevertheless complies with FMVSS No. 108 (ex: it is permissible to switch a clear bulb behind a red lens with a red bulb behind a clear lens).
NHTSA will initiate a rulemaking to propose a change to FMVSS No. 108 whereby these alternatively designed lamps (other than headlamps) may be sold in pairs as long as the instructions direct the purchaser to install both lamps simultaneously. Compliance with location and colour requirements would be based on the pair of lamps rather than the individual lamp.
Pending completion of the rulemaking, NHTSA will not enforce the location and colour requirements for replacement lamps sold in pairs if they include all of the functions of the lamps they replace. Nevertheless, NHTSA will not allow functions to be moved from one lamp to another lamp (ex: moving the reflex reflectors from the taillamp to a trunk lamp).