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

Monday, October 6, 2003

What color is your headlamp? Reducing glare and improving road safety
Transportation lighting researchers are studying roadway visibility and glare from vehicle forward lighting and are working with a variety of organizations to help drivers and improve safety.

Working with a number of government agencies, manufacturers, and research groups, transportation lighting researchers at the LRC are learning more about how automotive headlamps provide visibility and what can be done to reduce any problems drivers may face on the road at night.

In the last ten years, automobile manufacturers have implemented new light sources into headlamps, changing the lamps’ oncoming appearance. “The new headlamp source technologies we are seeing on the roads these days are one factor in increased reports of glare from drivers,” said Dr. John Van Derlofske, head of the Transportation Lighting Group at the LRC. In particular, the new high-intensity discharge (HID) or xenon headlamps are one technology cited in complaints, he said.

As a result, the LRC and its Transportation Lighting Alliance (a partnership of researchers, vehicle lighting manufacturers, and government agencies) have completed several investigations into the what, why, and how of headlamps and their effects on drivers.

Researchers look at headlamp characteristics, relationship to glare

Van Derlofske and colleagues recently completed a study for the National Highway Traffic Safety Administration (NHTSA) on the effect of headlamp parameters on glare. They looked at issues of spectral content, headlamp size, and illuminance at the eye to gauge both discomfort glare and disability glare. Of note, the LRC found that illuminance at the eye plays the most significant role in both discomfort and disability glare, while lamp spectra plays no significant role in disability glare and a smaller role in discomfort glare. Under the conditions tested, headlamp size did not play a significant role in either type of glare. The LRC also examined the effects of dimming headlamps under high ambient-lighting conditions to reduce glare.

“We found that under the conditions tested, headlamps can be dimmed to a certain extent without significantly impacting visual performance,” said Van Derlofske. The team presented these results at the Progress in Automotive Lighting Symposium in Darmstadt, Germany at the end of September,

Van Derlofske said this project has led to a larger follow-up study to glean more information about headlamp glare and visual performance. The first phase of the 16-month, $700,000 study will include a look at how people readapt after exposure to oncoming headlights, a survey of headlamp mis-aim, and a naturalistic data study on drivers’ length of exposure to glare. The second phase will explore the impact of advanced front lighting systems, a type of automated system that optimizes the light distribution of headlamps for specific driving conditions.

In that same field, the Transportation Lighting Alliance (TLA), administered by the LRC, has been studying headlamp spectra and its relationship to discomfort glare. Experimental results show that the discomfort glare response may be driven by short-wavelength light energy. From these results, a newly developed discomfort glare spectral sensitivity function was developed from a combination of photopic and short-wavelength cone responses. “Based on the data we gathered and the new sensitivity function, we now have the potential to spectrally tune light to reduce glare,” said Van Derlofske. A paper detailing the results is forthcoming.

LRC and TLA foster relations with transportation agencies, vehicle lighting associations

Van Derlofske said the LRC and TLA are continuing to develop relationships with federal transportation agencies and other transportation organizations. TLA recently joined the Motor Vehicle Lighting Council, a new organization formed under the auspices of the Motor & Equipment Manufacturers Association (MEMA).

The scientists are also working on research roadmaps to define future activities. The LRC organized and led a roundtable session with the Federal Highway Administration (FHWA) to develop a visibility research agenda to meet federal traffic safety goals. “With the aid of a diverse group of roadway visibility experts, we hope to set the vision for roadway visibility research for the next 10 years,” said Van Derlofske. He said they are now in the process of sorting through the information discussed and developing a list of research priorities.

TLA is also setting its sights on the future, particularly in the area of vehicle forward lighting. Van Derlofske says TLA is performing a scoping study to look for ways it can fill gaps in research and evaluate forward lighting more effectively.

For more information about the LRC’s Transportation Lighting Group and TLA, please visit the Transportation Lighting web site.

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

© 2003 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

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