The on effect of changes in curve geometry magnitude estimates of road-like perspective curvature

This study investigated the perception of curvature of perspectively viewed road-like curves in two-dimensional display. The effects of the geometric variables curve radius and curve angle, as well as the influence of experimental instructions, were assessed in a factorial laboratory experiment. Subjects estimated the magnitude of curvature of a series of stimulus curves in relation to a standard view. The results showed that decreasing the curve angle led to perceptual flattening of these curves. Reductions in curve radius resulted in a paradoxical decrease in perceived curvature. Judgments of curvature were the same for uninstructed subjects and those instructed in the meaning of physical curvature. These findings are in contrast to those expected from curve geometry and highlight an illusion in perceived curvature potentially harmful for curve negotiation on the road.