Visual environment in road traffic

The functions of the visual system and the environmental characteristics of roads are analyzed for daylight traffic and are compared with night time conditions. The aim of visual information is to show the presence of obstacles, changes or events which must be taken into account in the decision process. The human visual system is a daylight visual system. At the lowest levels of light there are physiological and psychological defects. In daylight traffic there is usually a considerable amount of available data. The problem is that of selection and of using only the most important information for provision. But at night, because of the disadvantages of the visual system, information is far from clear and often below the visual threshold if long distances are involved. At night, the risk of accidents is much greater than during the day. Additional measures for night traffic must aim at improving light and signal conditions. The role played by CIE technical committees in solving these problems is outlined together with some proposals for the revision of the organization of these technical committees. (TRRL)