The Insurance Institute for Highway Safety (IIHS) in the US has revealed its first-ever headlight ratings. A total of 82 headlight variants were tested from 31 different midsize models in the country, and believe it or not, just one car managed to walk away with a “good” score.

Which car do you think that was? The W205 Mercedes-Benz C-Class with its Intelligent Light System? The BMW 3 Series with its new full-LED headlights? Surprisingly, all lighting variations for the pricey C-Class fell into the “poor” category while the 3er’s top-shelf LEDs were only good enough for a “marginal” rating.

The only car to achieve a “good” score was the Toyota Prius v, equipped with its optional LED lighting and high-beam assist. A total of 11 cars fell into the “acceptable” category, with nine in “marginal” and 10 in “poor.”

Test results for Toyota Prius (left) and Mercedes-Benz C-Class. Click to enlarge.

“The Prius v’s LED low beams should give a driver traveling straight at 70 mp/h (112 km/h) enough time to identify an obstacle on the right side of the road, where the light is best, and brake to a stop,” said Matthew Brumbelow, an IIHS senior research engineer. However, when equipped with its base-spec halogen bulbs, the Prius fell right into the “poor” category.

The IIHS explains that the lighting systems were evaluated after dark and on a track within its Vehicle Research Centre. Using a special light measurement tool, low and high beams were tested on five different approaches — traveling straight, a sharp left curve, a sharp right curve, a gradual left curve and a gradual right curve.

While many of the cars were equipped with vertically adjustable headlights, the IIHS said that it preferred to test cars “as received from the dealer.” It does so on the belief that drivers just don’t take the time to manually adjust the vertical aim of their beams, and that manufacturers advise against it anyway.

Click to enlarge full results.

Which headlights were the worst, you ask? Well, look no further than the BMW 3 Series’ halogen bulbs. The IIHS says that when it’s dark, a driver with those headlights would have to be going 35 mp/h (56 km/h) or slower to stop in time for an obstacle in the travel lane. Thankfully, all BMW 3 Series variants in Malaysia are equipped with LED lighting as standard.

While curve-adaptive lighting systems appear to be a premium option, the IIHS says that these systems aren’t always the most helpful – especially to other drivers on the road. In the case of the Kia Optima, for example, its curve-adaptive lighting offered better road illumination for drivers, but created a significant amount of blinding glare for oncoming vehicles — despite being on its low beams.

On a stranger note, the Honda Accord’s LED system with high-beam assist scored a “marginal” rating while its basic halogen lights actually scored better, moving it up into the “acceptable” category. However, keep in mind that all of the models mentioned and tested here belong to the US-market. Right-hand drive variants may have differing results.