The rain sensor (7) is located on a windscreen and coves an area (6) with a width equal to the width of the area (4) swept by the wiper (2). The area covered by the sensor can be of indium-tin oxide or chromium nitride. The coverage area can extend into the area swept by the wiper or a dark coloured section of the windscreen. A further sensor can be provided in the wiped area of the screen or one covering the area behind the rear view mirror.
