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

Friday, October 3, 2003

Driven to distraction: does task load hinder driving?

Drivers use their peripheral vision to detect potential hazards in adjacent areas such as pedestrians or animals about to cross the roadway. These drivers, however, are often busy with other mental tasks as they drive. Dr. Yukio Akashi and LRC graduate student Jason Neches studied the effect these mental tasks have on a driver’s ability to detect potential hazards along the roadway.

They presented their findings in a paper, “The Effects of Task Load on Peripheral Target Detection,” at the 2003 CIE (the International Commission on Illumination) Conference held this summer in San Diego, Calif.

“Mental task load while driving and other peripheral vision factors may interact with each other,” said Dr. Akashi. The influence of roadway lighting on a driver’s peripheral target detection is often larger than that seen in controlled laboratory studies. “So to investigate how task load affects the impact of lamp spectral power distribution (SPD) on peripheral target detection, we conducted an experiment involving two SPD conditions at mesopic light levels.” Mesopic refers to low light levels, not completely dark, in which a person is able to discern colors. Driving down a lighted roadway at night is an example of mesopic light levels.

The subjects in the laboratory experiment carried out a tracking task while performing mental calculations as well as peripheral target detection. Specifically, while using a hand control to maneuver an electronic pointer over a moving target directly ahead, they were asked to perform math calculations and react to sudden appearances of off-axis targets in the peripheral regions of their field of view. Their reaction times were recorded under different task loads, including no tasks, tracking, math calculations, and both tracking and math.

The results suggested that reaction time to peripheral target detection increases as physical and mental task load increases. A driver talking on a cell phone, for example, will likely have a slower reaction time than a driver focusing only on driving. The study also found that as the off-axis targets moved away from the center line, reaction time increased.

Two types of “street lighting” were used in this study: metal halide and high pressure sodium lamps. Dr. Akashi says the experiment clearly showed that peripheral target detection was better under the metal halide lighting than under high pressure sodium.

As for the impact of SPD on peripheral target detection, according to Dr. Akashi, the impact of lamp SPD on peripheral target detection may have increased as task load increased, but this preliminary study failed to prove that.

“We wanted to bridge the gap between laboratory studies and the real world,” says Dr. Akashi. This study does that. But, he says, it also demonstrates a need for a more complete study.


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



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