The concept of "useful field of view" (UFOV) was introduced to describe the area from which useful visual information can be extracted in a single glance. It is not restricted to the fovea, nor does it involve the entire visual field. It is often claimed that the UFOV decreases with age, with increasing speed of travel, or under the influence of drugs or stress. However, this potentially important tool for the evaluation of the role of human sensorial factors in road safety suffers from a lack of measurement techniques. Within this framework, the ability of human observers to discriminate variations in their direction of heading from optical flow patterns simulating self-motion relative to a simple toric surface (a curved "tunnel") was evaluated. The perceptual performance was investigated as a function of the part of the global optical flow observers were looking at. Inasmuch as experimental laboratory data can be generalised to the complex task of driving, the results suggest that the perception of heading is optimal in a limited part of the visual field, situated around the future direction of travel. They offer a novel approach to the concept of useful field of view. They can be discussed in terms of their implications for road infrastructure design and for the positioning of warning and traffic signs within the driver's dynamic visual environment.
Samenvatting