Researchers at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute are studying HID (high-intensity-discharge) headlights, those bright bluish or greenish headlights now seen on more expensive European imports cars. The headlights are raising concerns
nationwide from drivers who complain about blinding glare.
LRC researchers John Van Derlofske, John D. Bullough and Claudia M. Hunter, reported their findings at a recent world congress of the Society of Automotive Engineers. Their study was commissioned by Philips Automotive Lighting, an LRC Partner and a major manufacturer of HID lamps.
Van Derlofske is the head of transportation lighting at the Lighting Research Center. He says HID headlamps enable drivers to see more effectively at night than conventional tungsten-halogen lights. His team conducted field experiments in which drivers responded to objects in their field of vision while using both sorts of lighting. Their study concluded that drivers using HIDs were better at "detecting edge-of-roadway hazards, such as pedestrians and animals."
"They (HID headlamps) produce more light, last longer, and use less energy," Van Derlofske said. "There's no question they result in better visual performance. We have now quantified that."
His colleague, John Bullough, explained the study in a news report on NBC TV's Nightly News with Tom Brokaw on June 12. That story highlighted the controversy over the lights, commonly referred to as "xenon" headlights. Drivers are complaining that the new xenon or HID lights blind them as they approach vehicles equipped with them.
But, there is another side of the story. Because HID lamps produce a wider beam, drivers can see better along the sides of the road, says
Bullough. "That wider beam allows drivers to see pedestrians or animals that may not quite be on the road, but might be approaching it," Bullough said. "So there are some potential benefits in terms of safety for the drivers who have these lamps." That benefit would extend to people walking along the roadway as well.
HID headlamps are widely used in European automobiles and are becoming increasingly popular in the United States. With the growing numbers
of HID headlamps, however, come growing numbers of complaints-more than one hundred to the U.S. Department of Transportation, which is calling for more studies. The National Highway Traffic Safety Administration weighed in on the issue, ruling that HIDs do not exceed maximum illumination standards. But debate over the pros and cons of the bright headlamps is growing nationwide, capturing the attention of news media. The LRC report was also mentioned in a June 7 article in USA Today that examined the controversy over HID headlamps.
While citing HID benefits, the study at the Lighting Research Center, acknowledges criticisms leveled against the lamps. The report said the same properties that allow HID systems to produce greater visual performance may cause them to produce more glare, and it urges further study to quantify HID glare. "The problem with glare," says John Van Derlofske, "should be weighed against the improved visual benefits."