Minimum Light Above Horizontal of Low-Beam Headlamps for Nighttime Legibility of Traffic Signs

摘要

The study had two goals. First, to develop a method for determining minimum levels of low-beam illumination above horizontal for legibility of retroreflective traffic signs. Second, to provide initial guidance concerning actual critical angles and corresponding intensity values. The developed method involves determining (1) relevant angles above horizontal, (2) desirable sign luminance, and (3) relationship between headlamp intensity and sign luminance for the relevant angles and different types of sign materials. Using the method, relevant angles and corresponding required intensity to achieve a given sign luminance were derived.