The relationship between illumination and traffic safety has been investigated using three different methods: (a) Possible connection between lighting and traffic safety, based on the comparison of accidents on illuminated and non-illuminated roads. Attempts were also made to relate the quality of illumination and the traffic accident rate; (b) Investigation of illumination requirements for detection of critical size objects under field conditions (as a criterion in determining visual needs for safe driving; and (c) Laboratory experiments to test the driver's visual performance under variable lighting system characteristics. The first method of investigation led to the conclusion that in general illumination favourably influences the night/day accident ratio. The relationship between the quality of illumination and the accident rate cannot be expressed in precise mathematical format because of the effect on accidents by other powerful factors such as road geometry, traffic volume and speed. The results of the field observations and laboratory experiments led to the description of the lighting system characteristics required to detect a critical size object at safe stopping sight distance. In addition to scientific data on the driver's visual performance and field test results on object detection, the report includes the methods of lighting system calculation and recommendations for effective implementation of the research findings in engineering practice. (Author/publisher)
Abstract