VISUAL PERFORMANCE UNDER NIGHT DRIVING CONDITIONS

Traffic safety is closely linked with the amount of visual information the driver can obtain on the road and its environment. The ability of perception can be described by the basic visual functions such as luminance contrast sensitivity and form perception and the influence that age has in these functions due to changes in the optical properties of the eye media. The luminance difference threshold as obtained in the laboratory can serve only as a basis to reveal the perceptibility of objects because the observation conditions are different from those given in practice. Roper and Howard found a factor of four to account for that difference. This threshold elevation facilitates perception of the form of the object. Consequently, the criterion of form perception, measured in terms of visual acuity, was used to investigate the visual behaviors in road lighting luminance levels. It occurred that for the perception of certain details the product of the contrast of the object and the level of the surrounding luminance remains constant. This reveals the fact that in the range of road lighting levels form perception is dependent only on the luminance difference of the objects to their background. The influence of age is briefly discussed.