Midsize Cars Fail to Light the Way in IIHS Headlight Tests

None of the base versions of 31 midsize cars tested by the Insurance Institute for Highway Safety received the group’s highest “good” rating for headlight performance.

The Toyota Prius V earned a good rating when equipped with optional light-emitting-diode headlights and high-beam assist. It was the only vehicle to do so out of 82 headlight packages tested on the 31 vehicles. The Prius V with standard halogen lights was rated “poor,” the worst of IIHS’s four categories.

Of the other 30 midsize cars tested with their best available headlight package, 11 received a second-best “acceptable” rating, nine were deemed “marginal” and 10 were graded as poor.

All vehicles meet U.S. standards for headlights. But IIHS notes that government rules allow for significant variation in the amount of illumination that headlights provide during real-world driving.

In its headlight tests—a first for the Arlington, Va.-based insurance industry group—IIHS evaluated the visibility provided and glare generated by a vehicle’s low- and high-beam lights from five different driving angles.

The vehicles were tested as they were received from dealers without adjusting the aim of the headlights. Some vehicles would have received higher ratings if the lights were properly aimed, IIHS says, but it notes that consumers rarely make such adjustments.

Vehicles equipped with high-beam assist, which automatically switches between high and low beams depending on the presence of other vehicles, can earn back some points taken off for inadequate low beam visibility. A vehicle that generated “excessive” glare to oncoming drivers on any of the driving approaches can't earn a rating above marginal in IIHS's system.

Among the 44 headlight systems with a poor rating, the low-beam halogen lights on the BMW 3 Series performed the worst, projecting about 130 ft down the road. IIHS says a driver with those headlights would have to be going 35 mph or slower (driving in a straight line) to stop in time to avoid an obstacle once it becomes visible. By comparison, the Prius V low-beam LED lights project 400 ft, allowing it to identify potential hazards and still stop in time when traveling twice as fast.

Optional curve-adaptive headlights, which swivel according to steering input, didn’t always score better than a vehicle’s standard lights. This is due in part, IIHS says, to the excessive glare these systems tend to generate.