This empirical study was designed to investigate the effects of mirrors with large radiuses (up to 8900 mm). Subjects' distance perceptions for objects seen in large-radius rearview mirrors were measured by magnitude estimation in a static field setting. The results indicate that: (1) overestimation of distance continues to decrease as mirror radius increases beyond 2000 mm; and (2) that the overestimation continues to be substantially lower than would be predicted from a model based on image minification and reduction of visual angle. However, even at the longest radius examined in this experiment (8900 mm) the overestimation of distance (8%) is not small enough to be dismissed definitively as trivial. Because various learning effects and changes in driver strategy may compensate for the distortion of distance perception, this does not necessarily mean that convex mirrors of any radius are unsafe. But it suggests that: (i) even for convex mirrors with very long radiuses, the gain in quantity of field of view provided by the convexity comes with a nontrivial cost in quality of field of view; and (ii) that the tradeoff between these two characteristics must still be considered in designing optimal mirrors. (A)
Abstract