Abstract: A method via which the range of vision in a vehicle's field of view can be determined precisely, so that with the help of range-of-vision information the driver can be advised to modify his driving style. The contrast of an object detected by a radar or lidar sensor is measured by a monocular video sensor, and the range of vision is determined from the measured values supplied by the radar or lidar sensor and by the monocular video sensor. Alternatively, the distance to and contrast of at least one object can be measured by a binocular video sensor, the range of vision then being determined from the measured contrast and distance values.