Samenvatting
In natural surroundings, vision gives man an immediate and realistic percept of space and movement, on the basis of which be is able to move and act without difficulty. In road traffic most information acquired by road users is of the natural type characterized by a built-in feedback. If the information is not obeyed, an accident may result. Symbolic information should also be designed that some kind of feedback is given. (for instance road humps for speed feedback).