Abstract
Theory and practice are discussed, with emphasis on disadvantages, including loss of light, incorrect alignment of plane of polarization by vehicle movements, and particularly depolarization by extraneous reflections, rain and fog, Some advantages over the usual sheet form polarizer would be provided by converting the light from plane to circular polarization; also by an evaporated multi-layer polarizer for the headlamps. Available techniques are not thought to offer a complete solution to the problem.