The Volkswagen rain sensor automatically regulates the intermittent wipe intervals of the windscreen wiper according to the intensity of the rain. The sensor is housed in the base of the interior mirror. It consists of a number of infrared light-emitting diodes (LEDs) and a central photodiode. The light emitted by the LEDs is reflected by the windscreen onto the photo sensor. The more drops of water there are on the windscreen, the less light the sensor receives. This information is passed to an electronic control unit which adapts the wipe intervals of the windscreen wiper accordingly. The sensitivity of the sensor can be additionally customised by way of a selector switch. The rain sensor is designed such that minor defects, dirt and ageing of the windscreen do not impair its functionality. The benefits of the rain sensor are comfort and safety. The driver is able to concentrate fully on the road, without having to worry about adjusting the wipe interval. This is a major boost to safety, particularly when visibility is suddenly impaired while overtaking trucks on a wet road, for example.