An analysis was made of the factors influencing the driver's subjective judgment of illumination pattern quality for the purpose of determining the optimum illumination pattern of low-beam headlamps. The results indicated that obstacle visibility distance is not the only factor influencing the driver's judgment of the quality an illumination pattern. The perceived brightness of the road surface, especially in zones near the vehicle and at an intermediate distance, was also found to have a large effect on the driver's judgment.

This paper first describes a new methodology for simulating low-beam illumination patterns which employs an image processing system. It then presents an analysis of perceived brightness and describes an attempt to devise a brightness quantification method.