Citation

Wolf E, McFarland RA, Zigler M. Highw. Res. Board bull. 1960; 255: 30-46.

Copyright

(Copyright © 1960, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Tinted windshields and side windows in automobiles have been introduced for two purposes: (1) to eliminate a major portion of radiant infra-red energy, and (2) to reduce excessive brightness and glare. The commonly used bluish- green tinted glass has a transmission of 65 to 70 percent, which is similar to that of sunglasses of light shade. At photopic (daylight) luminance levels the absorption of the glass is hardly noticeable. At mesopic (dusk) and scotopic (night) luminance levels a 30 percent reduction in transmission may interfere seriously with vision. To study the effects of tinted windshield glass on vision at various luminances, tests were performed on (1) dark adaptation, (2) recovery from the shock of a blinding light flash, (3) visual acuity, (4) depth perception, and (5) the effects of glare. Dark adaptation tests showed that when looking through a tinted windshield the thresholds for recognition of a test stimulus were higher than without an absorptive filter in the light path. The rise in threshold corresponded exactly to the brightness loss produced by the tinted glass. When the eyes were adapted to low levels of luminance or to complete darkness and were suddenly exposed to a bright flash of light, recovery from the light shock and regaining of the previous sensitivity level was not enhanced by the presence of the tinted windshield glass. Visual acuity was reduced slightly by tinted windshield glass. When acuity was measured with targets of small differences in size (landolt rings) it was found that with the tinted windshield the intrinsic details could be seen only if they are 10 to 20 percent larger than when seen without an absorptive filter in the path of light. Depth perception was also influenced by tinted windshield glass. A 25 to 35 percent loss in depth perception was observed when the test object was seen through tinted windshield glass. When test targets were identified in the vicinity of a glare source and the ratios of glare luminance/target luminance were determined when the targets are viewed through tinted windshield glass and without the filter, it was found that the ratios remained the same whether tinted windshield glass was in the path of view, or vision was not obstructed by filters.