U.S. Approval of Smart Headlights Has a Catch: They Can’t Be Too Bright

The federal government this week approved the use of adaptive driving beam headlights, bringing the United States in line with a standard that has been in place around the world for decades.

The light technology gives drivers the ability to essentially drive with their high beams on all the time, while the beam continually reshapes itself to avoid blinding oncoming drivers. The ruling came with a caveat, however: The lights will have to be dimmer than those used in Europe, for example, owing to a standard set in the United States in the 1970s.

The approval, on Tuesday from the National Highway Traffic Safety Administration, was given 18 months sooner than required by a section in the recently passed infrastructure act.

A.D.B. headlights have been available in virtually every country except the United States, where separate high and low beams have been the required standard. Manufacturers will soon be able to offer these advanced headlight systems to American drivers as well.

However, the A.D.B. system allowed by the federal agency will not be identical to those used in the rest of the world. While the infrastructure bill called for the standard approved by the Society of Automotive Engineers, which is similar to the system used in most other countries, the agency modified it, citing in its 326-page rule a Supreme Court decision that gave it the right to do so.

The problem, according to one lighting expert, is that while U.S. vehicles can soon be equipped with headlamps that use dynamically reshaping high beams to prevent glare, their light output still cannot exceed the standard set in the 1970s, which is a fraction of the light intensity allowed globally.

“Adaptive driving beam technology in the rest of the world can increase seeing and reduce glare to a greater degree than what NHTSA has specified,” said Daniel Stern, chief editor of Driving Vision News, a technical journal about global vehicle lighting and driver assistance systems.

“The U.S. has left in place an ancient cap on high-beam intensity from the late 1970s,” Mr. Stern said. “It’s a regulatory island.”

Given the length of the report, few have had the opportunity to digest its contents. Both General Motors and the Society of Automotive Engineers have reserved judgment on the new smart headlight rules.

Nor do carmakers that have already included deactivated A.D.B. lights in their vehicles yet know how or if the lights will meet the new government standard.

“We’re encouraged by the fact that the ruling was made,” said Mark Dahncke, director of communications for Audi of America. “Now we’re evaluating the impact on our existing and future lighting systems. We look to make A.D.B. lighting available to our customers as soon as we can.”