Do High-Intensity Discharge Headlamps Cause Glare?

Do High-Intensity Discharge Headlamps Cause Glare? n 2001, the National Highway Traffic Safety Administration (NHTSA) asked the public to submit Icomments about headlight glare and visibility. By April 2002, NHTSA had received more than 1700 responses! The LRC is assisting NHTSA and headlamp manufacturers as they weigh the benefits of high-intensity discharge (HID) headlamps and the obstacles they face as the technology matures. The LRC’s work with HID headlamps We have worked with Philips Automotive Lighting to study the effect of HID headlamps on forward visibility. Our work, featured on NBC Nightly News and in USA Today, shows that HID headlamps improve peripheral target detection versus conventional halogen headlamps. In order to understand better how headlamp intensity and spectrum affect visual discomfort, we completed a prelimi- nary study of headlamp glare using halogen, HID, and blue-filtered halogen lamps. Subjects rated their discomfort levels (1=unbearable, 9=just noticeable) and identified the minimum contrast of objects that were visible with each glare source. The results showed that • Headlamps with more short-wavelength light (~450 nm) resulted in greater discomfort than lamps with less short- wavelength content. Implications • There were no differences among the headlamps in terms If validated in the field, these results could be used to of the minimum contrast that was detectable in the optimize the spectra of HID headlamps to minimize short- presence of glare. wavelength (~450 nm) light while increasing light in the scotopic (~510 nm) region, which could minimize discomfort while improving peripheral detection. NHTSA and headlamp manufacturers will need to continue working together to identify headlamp characteristics that are optimal for visibility while reducing potential for glare. The LRC is in an ideal position to assist both groups in making informed decisions.

The LRC will continue to study these headlamps in further laboratory and field studies commissioned by NHTSA.

Sponsors eserved. National Highway Traffic Safety Administration Philips Automotive Lighting Westat, Inc. Lighting Research Center Lighting Research Center, Rensselaer Polytechnic Institute • Troy, NY 12180-3590 • Telephone: (518) 687-7100 • Fax: (518) 687-7120 • Internet e-mail: [email protected] • Web Site: http://www.lrc.rpi.edu