The visual cut-off angle of vehicle windscreens

Abstract

The glare from road light lighting installations as experienced by car drivers is determined to a large extent by the visual cut-off angle of the windscreen. The present study is set up to assess this angle. Based on samples totalling 950 vehicles it is found that the log-value of the angle is normally distributed, the mean being 24 degree, the 97.5% and the 2.5% values being 44 degree and 13.5 degree respectively. As these values differ considerably from the values traditionally used in the quantification of glare, it seems necessary to reconsider the current system to assess glare.