High beam intensity and obstacle visibility

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Abstract
Visibility distances to obstacles on the right hand side of a straight two-lane road have been obtained. In high beam with opposing high beam of about the same intensity there are no significant differences in the visibility distance as a function of high beam intensity over about 50000 cd. In high beam with opposing high beam of intensity about three times as large or more there is a large loss in visibility distance (>35%) compared with the situation above. The optimum distance for switching from high to low beam varied between 250 m and 400 m when the two opposing vehicles had about the same high beam intensity. In high beam without opposing glare there is very little gain in visibility in relation to the amount of increase of intensity above 50 000 cd.