Apart from LIDARs, self-driving cars are also deployed with long-range radars. One of the popular long-range radars is ARS 30X by Continental (http://www.conti-online.com/www/industrial_sensors_de_en/themes/ars_300_en.html). It works using the Doppler principle and can measure up to 200 meters. Bosch also manufactures radars suitable for self-driving cars. The main application of radars is collision avoidance. Commonly, radars are deployed at the front of the vehicles.