The relation between discomfort glare and driving behavior.

Author(s)
Theeuwes, J. & Alferdinck, J.W.A.M.
Year
Abstract

The present study investigated the effects of discomfort glare on actual driving behavior. The study aimed to provide a validation in terms of driving behavior of the widely used De Boer rating scale for measuring discomfort glare. Subjects (old and young; US and European) were exposed to glare of a light source mounted on the hood of an instrumented vehicle simulating headlamps of an oncoming car. The luminous intensity of the light source was either 350, 690 or 1380 cd. The two higher intensities were similar to the maximum glare intensities of European and US headlamp standards. Subjects drove at night the instrumented vehicle in actual traffic along a particular track consisting of urban, rural and highway stretches. Driving behavior and the detection of critical objects as well as various subjective measures of discomfort glare were determined. The results indicate that due to the glare source subjects adapted their behavior in a safe direction: on dark and winding roads subjects drove significantly slower and invested more effort when the glare source was on (690 and 1380 cd per headlamp) than when it was off. The two higher glare intensities (690 and 1380 cd) caused a significant drop in detecting objects erected along the road, both in terms of missed targets and detection distance. Older subjects showed the largest behavior adaptation and the largest drop in object detection performance. Furthermore, the results indicated that De Boer ratings on discomfort glare were not related to changes in driving behavior caused by the glare source: high levels of discomfort were not associated with a large reduction in driving speed nor with poor object detection performance. The finding that subjects adapted their behavior into a safe direction by reducing speed and/or investing more effort independent of the actual glare illuminance (i.e., within the ranges measured both US and European glare sources caused the same speed reduction) indicates that a glare illuminance of at least 1.1 lx (the maximum US level comparable to 1380 cd per headlamp) is acceptable as a maximum upper limit. It should be realized however that on a dark road, basically any glare illumination will cause a drop in object detection performance. (Author/publisher)

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Publication

Library number
20061671 ST [electronic version only]
Source

Soesterberg, TNO Human Factors Research Institute TM, 1996, 75 p., 39 ref.; Report TNO TM 1996 C-15 / Report DOT HS 808 452

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