Effects of Reduced Transmittance Film on Automobile Rear Window Visibility

Abstract

Deeply tinted window glass transmits less light than less deeply tinted glass and therefore reduces driver visibility. The task of looking through the rear window for hazards before backing a car was simulated in a laboratory setting with five targets (car, bicyclist, pedestrian, child, and debris) shown to drivers (ages 18-55, 56-75, and 76+) at various combinations of luminous transmittance of the windows and luminance (brightness) contrast of the targets. Analyses showed that the frequency of correct target detection varied by target. The car was always detected, but detection probability decreased with reduced luminous transmittance for the child and roadway debris targets. For the bicyclist, pedestrian, child, and debris targets, detection probability decreased with lower luminance contrast and for older age groups. The results suggest that the safety of backing maneuvers is compromised for all drivers at the darkest tinting levels studied. This is particularly true for elderly drivers for tinting levels darker than the 70% minimum luminous transmittance required by federal standards.