To provide a vehicle-mounted radar system using UWB (Ultra Wide Band ) communications which can easily detect the position and condition of an individual vehicle in addition to obstacles existing in the surroundings.

The vehicle-mounted radar system uses the UWB having a communications function and a radar function. The radar system measures the distance between one's own vehicle and an obstructive vehicle ahead by the radar function and issues a warning to a driver or performs a pre-crush operation in accordance with the distance. By allowing vehicles to notify the other vehicle of the position of one's own vehicle mutually using the communication function, the radar system measures the distance to a vehicle approaching one's own vehicle regardless of disturbances and issues a warning to the driver or performs a pre-crush operation in accordance with the distance. By changing the working frequency and transmission power of the radar by information on the position of one's own vehicle, interference with other wireless systems is reduced.