Visual information is essential in traffic: traffic lights tell us when to cross the street. Zebra crossings signalise visually street sections where car drivers have to pay special attention to pedestrians. Children are taught to look to the left and to the right before crossing the street. Motorists are aware of the problems and hazards occurring by darkness, rain, snow or fog when range of sight is decreased. A lot of accident avoidance deals with the issue to see and to be seen, e.g., the failure of motorists to detect and recognise motorcycles in traffic was regarded as the predominating cause of motorcycle accidents .
Blind and visually impaired people have to manage their way through a world of traffic which was mainly created for people with full eyesight. According to statistics compiled by the National Center for Health Statistics of the US Centers for Disease Control and Prevention, as summarised by the American Foundation for the Blind, in 1996, there were approximately 1.3 million legally blind people in the United States. 5.5 million elderly individuals are regarded as blind or visually impaired . As others, these individuals benefit from a barrier free architecture.
The idea of barrier free architecture is to provide a structure which enables everyone independently of his/her physical and mental condition to enter buildings, to move within them, and to use technical devices or other devices of daily life (as rest rooms or ticket machines) without major restrictions. Nowadays in western countries, the exclusion of handicapped people from everyday life’s activity is prohibited, e.g., in the US by the ‘Americans with Disabilities Act’ (ADA)  or in Germany by the ‘Equality Law of Disabled Persons’ (‘Behindertengleichstellungsgesetz’) . These rights were also brought up in a United Nations resolution (56/168) . Two aspects of barrier free architecture should be differentiated: one is the elimination of barriers, the second is the compensation of handicaps by appropriate designing and implementation of technical devices. Tactile floor indicators are thought to compensate the loss or impairment of vision by the provision of complementary haptic information.