The Effects of Image Size and Luminance Contrast on Object Detection and Discrimination in Cross View Mirrors

This report presents results from a performance evaluation study on the adequacy of the image size, within school bus cross view mirrors, mandated by FMVSS 111 The mandated image size is 9X3 minutes of arc (ie, 9′X3′) Six observers discriminated the orientation offset of three different image sizes (ie, 45′X15′, 9′X3′, 13.5′X45′) presented onto a banana type cross view mirror. The images were presented to observers under three luminance contrast levels 15%, 20%, and 25%. Results indicated that poor performance was associated with the 45′X15′ image size at all contrast levels and the 9′X3′ image size at a luminance contrast of 15%. The 135′X45′ image size was associated with good performance. In conclusion, measures of performance failed to demonstrate an unequivocal deficiency of the 9′X3′ image size.