THEORETICAL MODEL OF THE VISIBILITY LEVEL AND PRACTICAL MEANS OF ITS IMPLEMENTATION
Free (open access)
Volume 7 (2012), Issue 4
381 - 393
Driving a car, especially in city traffic, is a greatly complex process combining observation, recognition and psychomotoric functions. Safe, efficient and comfortable driving requires a specific level of visibility of road obstacles. The difficulty in spotting an obstacle in the road and in evaluating its effect on driving depends on such factors as lighting conditions in the road and its vicinity, presence of sources of glare, sources of distracting and attracting attention in the driver’s field of vision, for example, electronic outdoor advertising boards (LED billboards), the obstacle’s geometric and photometric properties, observation conditions and the driver’s visual performance. The research on the visibility of obstacles in the road has shown that the satisfaction of normative requirements in relation to average luminance and the general and longitudinal uniformity does not guarantee that an obstacle will be spotted. Thus, it is necessary to introduce another criterion to make it possible to evaluate the visibility of obstacles in the road. Visibility formula was described by Adrian in 1989 and applied with visibility levels in North America as quality criterion. For the purposes of designing road lighting systems, the visibility criterion is not used in European countries yet. Due to simplifications, other standards and requirements, it is also impossible to directly employ the visibility criterion used in United States, namely the Small Target Visibility, based to a large extent on Adrian’s visibility model.
Road lighting, road lighting standards, Small Target Visibility, visibility level