Discomfort Glare: Luminance Range-Limited Replication Study of Angularly Small Sources

Abstract

In 1977 in this Journal results were published which showed experimentally and statistically how to predict the discomfort glare for the typical observer on the roadway. This report includes two major steps forward over the previously-published work. One is a new experiment where we account for range effects by a closer simulation of roadway lighting conditions. The magnitude of the values of the 'borderline of comfort and discomfort' (BCD) was lowered because the luminance of the glare source was lowered. On the basis of evaluations of 62 test observers, the overall median BCD was determined. Another new element was an improved multiple regression analysis model which enables prediction of discomfort glare for glare source size, position and for background luminance. This regression model predicted 'typical' observer responses. In the presence of great individual differences such typical values might vary greatly from many observers responses. Thus, the new experiment has provided more appropriate data for applying discomfort glare to roadways.