But that could be changing. This year, for the first time, the institute will give its coveted highest safety rating, known as Top Safety Pick Plus, only to vehicles whose headlights receive a minimum “adequate” score.
The new focus on lights will most likely push automakers to ensure that their lamps not only shine brightly, but also do so far enough down the road. Already, BMW stopped offering the poorly rated halogen lamps on its 3 Series sedans; as a result, the car was designated a Top Safety Pick Plus.
“Headlamps have not been viewed as the safety component that they should be,” said Jennifer Stockburger, the director of operations for the auto test center for Consumer Reports, which also examines headlight quality.
The insurance institute first started testing headlights in 2016 to see how well lamps that swiveled around bends, known as curve-adaptive headlamps, would perform. It found that property damage liability claim rates fell 9 percent for those cars that had curve-adaptive headlamps.
Working with the University of Michigan Transportation Research Institute and the Consumers Union, the institute then developed headlamp performance standards. It designated how far both low and high beams should reach around curves and in a straightaway without providing glare.
To be rated acceptable, the second-highest rating, high-beam headlights have to shine at least 492 feet down the road, and 328 feet down the right side of the road on low settings.
By law, headlamps today can be of any shape, as long as the light output meets specifications set by the National Highway Traffic Safety Administration. Headlamps must also adequately avoid glare, or dazzle as it is known in Europe, for oncoming vehicles and pedestrians.
As a result, vehicle manufacturers generally put a lot of effort into making their headlights stand out as part of a vehicle’s design statement, creating lights that swoop, are flush to the body, or are angled in a way that reflects the vehicle’s sheet metal.
But minimum illumination distance is not mandated, and manufacturers self-certify that their lamps meet the light output criteria.
And once on the road, a variety of factors — including lamps that weren’t aimed properly at the factory or even springs that haven’t settled into place yet — can sharply reduce the ability of a headlamp to shine down the road or light up the important places.
Newer technologies, such as xenon and LED lamps, project light that is brighter and whiter than what traditional incandescent bulbs cast, giving the illusion that they are better. But if they’re incorrectly aimed, they can actually perform worse than older halogen systems, Mr. Lund of the insurance institute said.
When testing headlights, Consumer Reports aims the headlamp according to government specifications. The insurance institute tests lamps as they arrive on the vehicle from the manufacturer. The group says that method gives the consumer a better sense of real-world performance.
Regardless of approach, both groups have found vehicle makers to be responsive to their criticisms.
“The manufacturers are absolutely interested in our results,” said Ms. Stockburger of Consumer Reports. “They’ve changed the performance of their headlamps and improved them over the years that we’ve been testing.”
The insurance institute found a similar reaction.
The headlamp performance of BMW’s 2 Series xenon lamps went from “marginal” to “good,” simply by re-aiming the lamps.
Fiat Chrysler moved to LED lamps for all but the base model of the Jeep Wrangler, and now offers xenon lamps as an option on the Jeep Renegade.
And even better lighting systems could be coming soon.
One new system, generically known as adaptive driving beams, illuminates the road using around 50 to 100 distinct LEDs or, as in the case of BMW, a lamp that changes angles. The goal is to get the reach of high beams without throwing glare.
When onboard cameras sense oncoming vehicles or pedestrians, the lights can adjust automatically, either by dimming individual LEDs in the lamp or moving the light down and to the side, in essence providing always-on high beams without shining the beam into the eyes of other drivers.
Adaptive driving beam headlamps are available from several manufacturers, like Audi, the Opel division of General Motors and Mercedes-Benz in Europe, but they’re not yet legal in the United States. The National Highway Traffic Safety Administration, the agency that can change the rules, is now weighing recommendations to make those lights legal.
“We’re very excited about adaptive driving beams,” said David Hines, director of the agency’s office of crash avoidance standards. He would not predict when the standard would be approved, however.
Further into the future are pixel beam headlamps, essentially matrix beam headlamps on steroids. They will use more than a thousand individually controlled LEDs that turn on and off to light or mask small oncoming objects.
Developed by Osram and other lighting manufacturers, pixel beams will be able to shut light off to objects as small as a driver’s face, or a rearview mirror, said Bart Terburg, Osram’s automotive regulations manager. These new systems will start appearing on cars in about four years, he said.
The federal government will also soon join the insurance institute and Consumer Reports in providing headlamp ratings for prospective buyers, much as it now reports on crash-worthiness and fuel economy. It hopes that such data will appear beginning with model-year 2019 vehicles. Such ratings could also increase pressure on automakers to do a better job with lighting.
“We want to help illuminate the road,” Mr. Lund of the insurance institute said, “not just make cars prettier.”