The glare from headlights causes accidents, and the problem is getting worse as bulbs get brighter. One way to cut out glare is with a polarising filter that only lets light through that travels in a single direction, cutting out all the other light waves wiggling in random directions.
Back in the 1930s, the ingenious idea of using polarised headlights and a polarising filter in windscreens was suggested. Unfortunately, because of regulations, costs and the fact that polarising filters cut out too much light, the system was never introduced. Instead, the dimming rearview mirror was created, which can be flipped between a normal and dim reflection.
Today, automatic dimming mirrors are available, as well as special polarised driving glasses, which both help to cut down glare.
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