The Relation between and Driving Behavior Discomfort Glare

NHTSA - Behavioral Safety Researchhttps://doi.org/10.21949/15260201996PDFTech ReportTheeuwes, JanAlferdinck, Johan W A MTNO Human Factors Research InstituteUnited States. Department of Transportation. National Highway Traffic Safety AdministrationUnited States. Department of Transportation. National Highway Traffic Safety AdministrationUnited StatesGlareBehaviorHeadlampsLuminous intensityTravel behaviorRoad testsVisibilityDiscomfortDriving BehaviorHeadlamp lntensitiesHeadlamp StandardsDOT HS 8O8 452Final Report, Nov. 94-Dec. 95The present study investigated the effects of discomfort glare on actual driving behavior. 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 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 than when it was off. The two higher glare intensities caused a significant drop in detecting objects erected along the road. Older subjects showed the largest behavior adaptation and the largest drop in object detection performance. Furthermore, the results indicated that the widely used De Boer ratings on discomfort glare were not related to the actual changes in driving behavior. 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 suggests that a glare illuminance equivalent to the US headlamp standard is acceptable as a maximum upper limit.129