There may be a reason why people have trouble seeing while driving at night, and it's not their eyesight.
A new rating of the headlights of more than 30 midsized car models gave only one model a grade of “good.” Of the rest, about a third were rated “acceptable,” a third “marginal” and a third “poor”.
The difference between the top and bottom-rated models for a driver's ability to see down a dark road was substantial, according to the study released on Wednesday by the Insurance Institute for Highway Safety, an industry-funded organisation that evaluates automotive safety.
New Toyota Prius: The inside story
The LED headlights in the top trim level Toyota Prius V - the only one of 31 models tested to get the “good” rating - were able to illuminate a straight roadway sufficiently to see a pedestrian, bicyclist or obstacle up to 118 metres ahead. At that distance, the vehicle could be traveling up to 120km/h and still have time to stop.
But halogen headlights in the BMW 3 series, the worst-rated ones, were able to illuminate only 39 metres ahead. At that distance, the vehicle traveling at 60km/h would barely have time to stop, according to the study.
That's important because about half of all road fatalities happen at night or during dawn and dusk when visibility is lower.
The reason for the big performance gap is that there's a lot more to how well headlights help drivers see than merely the brightness of the bulb or even what type of bulb is used, said David Zuby, the institute's executive vice president and chief researcher.
“We found the same light bulb, depending upon what reflector or lens it's paired with and how it's mounted on the vehicle, can give you very different visibility down the road,” he said.
It gets more complicated. The report showed that you can't buy a more expensive model or add an expensive technology package and necessarily expect to get better headlights.
The halogen headlights in the economically priced base model four-door Honda Accord, for example, earned an acceptable rating while halogen and LED headlights in two pricier Mercedes-Benz models were rated poor.
Zuby said with no reliable clues such as the price of the car or the type of light, it's hard for motorists to figure out which vehicles will provide the safest visibility. He recommended car buyers check the institute's ratings on the Insurance Institute for Highway Safety website.
FIVE DIFFERENT APPROACHES
The report comes as halogen bulbs are being replaced by high-intensity discharge and LED lights in many vehicles. Headlights that swivel with the car's steering to help see around curves are also becoming more widespread. While these changes can have advantages, they don't guarantee good performance, the report said.
Researchers tested the headlights after dark at the institute's test track in Ruckersville, Virginia. A special device measured the light from both low beams and high beams as the vehicles were driven on five different approaches: traveling straight, a sharp left curve, a sharp right curve, a gradual left curve and a gradual right curve. Researchers also evaluated headlights for excessive glare.
Zuby said they were surprised to find how much headlights varied from the base model to higher trim or accessory packages. Eighty-two different headlight systems were available for the 31 current models assessed in the study.
To get the top-rated headlights in the Prius V, customers would have to specify the advanced technology package, which is only available in the top trim level. Standard halogen lights without high-beam assist in less expensive Prius V trim levels received a poor rating.
High-beam assist automatically adjusts the headlamp range for the distance of vehicles ahead or oncoming traffic.
Toyota officials declined to comment, and BMW officials didn't immediately reply to a request for comment.
Mercedes-Benz said in statement that it was “greatly surprised” by the test, and remains “confident our lighting systems provide important safety benefits for real world conditions”.
Zuby said government standards for judging the performance of headlights “are essentially unchanged” since they were set back in the 1960s.
“They measure the light coming out of the light source - right in front of the light bulb, in essence - and don’t look at how the light is projected down the road, which is what our tests do,” he said.
The institute hopes its study will encourage the National Highway Traffic Safety Administration to improve standards, or inspire automakers to make better headlights on their own, Zuby said.
