METHOD AND APPARATUS FOR DETECTING THE STATE OF HUMIDITY ON A ROAD ON WHICH A VEHICLE IS TRAVELLING

A vehicle travels along a road with its lights on because of the conditions outside the vehicle. It has an onboard optical sensor associated with the headlights and arranged to form an image of a zone of the road in front of the vehicle, so that the state of humidity of the road can be determined, and the light output modified accordingly. The zone concerned, on the road, consists of at least one segment oriented in the direction of travel, so that the image created by the optical sensor is a characteristic curve representing the light distribution on the road. This image is compared with a reference curve to determine the state of humidity. The reference curve represents light distribution when the road is dry.