Information taken from the literature enabled the dipped headlight intensity necessary for smooth and safe driving to be calculated. The required glare limitation and the homogeneity of the road luminance were both taken into account. The visibility of roadside objects was evaluated systematically during trial runs using three types of headlamp. The headlamps were as follows: (a) a headlamp with a conventional parabolic reflector; (b) a headlamp with a homofocal ellipsoidal reflector; and (c) a headlamp with a three-axis ellipsoidal reflector. The literature study showed that it was not possible to make substantial improvements in dipped headlight light intensity while maintaining sufficient glare restriction. The trial runs showed that there were only small differences between the different headlamp types. The headlamp with the three-axis ellipsoidal reflector produced a light intensity that was closest to the recommended value. A construction which maintains the correct vertical alignment of the headlamps during driving is considered essential in order to combine optimum illumination with optimum glare restriction. A wipe or spray installation on the headlamps frontal lens is also useful.
Abstract