Advancing the effective use of light for society and the environment.

Wednesday, January 12, 2005

LRC Helping to Design ‘Headlamps of Tomorrow’
LRC studies will lead to new headlamp designs and beam patterns for greater safety and visibility
Photo of car headlights at night

As automobiles and headlamp technologies become more sophisticated, the LRC’s growing transportation lighting program is fostering new research and using its expertise to inform governmental regulators and manufacturers about headlamp characteristics and performance issues.

A series of LRC studies conducted over the last two years and several still ongoing are providing greater knowledge to researchers about how headlamps help and hinder drivers.

“We’re using these studies to quantify visibility and glare from emerging headlamp technologies, as well as to understand how headlamp beam components provide information about road conditions,” says John Van Derlofske, Ph.D., the LRC’s head of transportation lighting. The safety impacts of new technologies, such as high-intensity discharge (HID) lamps, LED headlamps and advanced forward lighting systems, are still not completely understood. This has fueled debates among researchers, manufacturers and the government over the benefits and drawbacks of these systems. In the past year, National Highway Transportation Safety Administration (NHTSA) has sponsored LRC research to assess headlamps, including how they provide visibility, contribute to glare, and interact with outdoor lighting. Lighting manufacturers also have sponsored research on visibility with these new technologies.

LRC researcher adjusts headlamp test apparatus
An LRC researcher adjusts a headlamp test apparatus during a field study.

Evaluating driver performance with advanced forward lighting systems

One way to reduce glare from headlamps is to dim them. Proposed advanced forward lighting systems (AFS) offer multiple beam patterns for different road conditions and potentially could dim automatically when outdoor lighting is available. But these new systems bring forward new questions: How does dimming affect driver visibility? How much outdoor lighting is sufficient to allow dimming? How low can headlamps be dimmed? Can dimmed forward lighting actually reduce glare to oncoming drivers?

The LRC investigated these questions on a converted runway at Schenectady County Airport in Scotia, N.Y. LRC scientist Yukio Akashi, Ph.D., along with Dr. Van Derlofske and LRC scientist John Bullough, Ph.D., created an experimental roadway with portable high-pressure sodium streetlights. The researchers tested drivers’ detection of distant targets with a variety of headlamp intensities, ambient roadway illuminances, and glare sources. The LRC found that as ambient roadway lighting increased, so did the distance at which drivers could detect targets; however, oncoming glare reduced this detection by up to 30 meters. Dimming forward lighting was effective at reducing glare experienced by drivers. Overall, the LRC found that by dimming forward lighting systems, it may be possible to reduce glare from headlamps on lit roads without greatly impairing visibility.

“Vehicle lighting and street lighting may be conveying redundant information, so it is possible to reduce this redundancy by dimming headlamps, thereby mitigating glare,” says Dr. Akashi. He notes that AFS systems could be designed with photosensors to detect ambient illuminance and dim headlamps. However, it is still necessary, he says, to determine the lowest level of outdoor lighting at which headlamps can be dimmed.

In addition to this study, the LRC also has worked with NHTSA to identify available research of issues related to AFS systems. Based on this review, the LRC is now developing new AFS studies, identifying evaluation metrics for AFS, and designing its own prototype AFS.

Assessing headlamps’ contributions to glare

Dimming headlamps is one way to reduce glare, but LRC researchers say light level is not the only factor contributing to drivers’ discomfort at night. More than 5,000 people responded to a NHTSA request for comments on headlamp glare, and the majority of these comments focused on glare from newer technologies. “Many are complaining about not only high intensities, but also the bluish color of some lamps and small lamp size,” says Dr. Bullough. But while some find the new lamps disturbing, drivers behind the wheel of cars with HID and coated halogen headlamps are reporting better visibility, especially of objects on the side of the road.

To help NHTSA evaluate the issues brought forth in these complaints, the LRC conducted a field study to empirically examine the effects of oncoming headlamp intensity, color and size on visibility and impressions of discomfort. The LRC found that increasing the intensity of oncoming headlamps both decreased visibility and increased discomfort, while higher “blue” or short-wavelength content increased discomfort only. The size of oncoming headlamps did not affect visibility or comfort at all. Bullough says, “The LRC is now using these findings to get the full story of these headlamps out to decision makers,” including manufacturers, government, and the general public.

Naturalistic study to provide new information on road lighting and glare

While the LRC continues to look at other issues that may increase discomfort, such as mounting height and misaim of headlamps, the transportation lighting team also is analyzing how drivers respond to glare in real-world situations. NHTSA and Virginia Tech are providing data to the LRC from 100 cars outfitted with more than 100 sensors and five video cameras, which are collecting information such as speed, lane position and glare illuminance. “From these data we hope to determine other meaningful measures and tests of glare, beyond the traditional methods of target visibility and subjective ratings,” says Van Derlofske.

More information about these studies can be found in the LRC Project Portfolio:

Evaluating the Interaction of Fixed Roadway Lighting and Forward Vehicle Lighting pdf logo

Assessing Headlamps and Glare pdf logo

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.

© 2005 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

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