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LRC News

Tuesday, May 8, 2007
Field Study Examines Visual Performance for Drivers at Mesopic Light Levels

By Keith Toomey

Street lighting used in mesopic lighting field study
Street lighting used in mesopic lighting field study
LRC researchers conducted a field study to extend fundamental findings about visual performance at mesopic light levels in a driving context. Study subjects drove a vehicle along a lighted street while performing a high-order decision-making task. They identified the direction of an off-axis target, toward or away from the street, and either braked or accelerated, accordingly.

The study, conducted by Yukio Akashi, Mark S. Rea, and John D. Bullough, compared two sets of light sources: ceramic metal halide and high-pressure sodium. The same study was also performed during the daytime. The results demonstrated that both braking and acceleration response times decreased monotonically as unified luminance increased, suggesting that unified luminance is a suitable rectifying variable for characterizing light levels for different light sources with respect to a complex visual task.

As shown in previous studies, this study showed that off-axis response times under a ‘white’ metal halide light source are shorter than they are under high-pressure sodium at the same photopic light levels. However, this study also demonstrated that task performance improves as a function of unified luminance, even for a realistic high-order visual task.
Researchers set up street lighting for mesopic lighting field study
Researchers set up street lighting for mesopic lighting field study
And, because improved peripheral visibility may not be consciously appreciated by drivers, they will not necessarily change their driving behavior. Therefore, improved peripheral vision may lead to greater driver safety.

This study’s findings are presented in “Driver decision making in response to peripheral moving targets under mesopic light levels,” and can be found in the journal, Lighting Research and Technology, Vol. 39, No. 1, pages 53-67 (2007). This paper is available from the publisher at http://lrt.sagepub.com/cgi/content/abstract/39/1/53.

About the Lighting Research Center

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute of Troy, N.Y., and is the leading university-based research center devoted to lighting. The LRC offers the world's premier graduate education in lighting, including one- and two-year master's programs and a Ph.D. program. Since 1988 the LRC has built an international reputation as a reliable source for objective information about lighting technologies, applications, and products. The LRC also provides training programs for government agencies, utilities, contractors, lighting designers, and other lighting professionals. Visit http://www.lrc.rpi.edu.

Contact:lrcnewsletter@rpi.eduPhotos & Graphics:Dennis Guyon
Editor:Keith ToomeyWeb Production:Joann Coffey
Contributing Writers:Jennifer Taylor, Keith Toomey, Dennis Guyon
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