Why U.S. Adaptive Driving Beam Headlight Rules Took Years to Finalize

In 2013, in response to Toyota’s petition, the National Highway Traffic Safety Administration (NHTSA) announced that it would begin a rulemaking process for adaptive driving beam (ADB) headlights. It took another five years for the proposed rules to be published for consideration.

During that time, NHTSA considered adopting Europe’s approach. However, the agency ultimately decided that adaptive beam headlights could struggle in situations where they do not detect another vehicle quickly enough. As NHTSA explained, if a car with adaptive beam lights “cannot see another vehicle in front of it for a long time, such as in an intersection scenario or when two vehicles come toward each other on a curved road, the ADB does not have sufficient time to react to adapt the beam pattern.”

How U.S. and European headlight regulations differ

One important difference involves how vehicles are regulated. In Europe, cars receive type approval. The manufacturer submits a vehicle to authorities for testing to confirm that it complies with regulations, and the authorities approve the car for sale.

In the United States, automakers must tell NHTSA that their vehicles comply with the Federal Motor Vehicle Safety Standards (FMVSS). They can face sanctions if that certification is later determined to be false.

At the time, NHTSA believed that Europe’s glare test was too subjective for the U.S. self-certification system. The agency therefore decided to create its own certification process for adaptive driving beam headlights.

U.S. rules for adaptive beam headlights

NHTSA completed its final rule in 2022. Since then, vehicles with active beam matrix LED headlights have been sold in the United States. Audi’s new large SUV is one example, although its system has limited functionality compared with the same technology in European-spec vehicles.

What FMVSS 108 is intended to address

Among NHTSA’s goals for the latest version of FMVSS 108 are harmonizing U.S. lighting standards with global standards and updating regulations for technologies such as:

• LED lighting
• Ambient light sensors
• Automatic high beams
• Replaceable light sources

The updated standard also aims to improve testing procedures for lenses and optics and to better understand how headlights should be aimed—all while ensuring that adaptive systems do not blind other drivers with glare.