RPAS is a Rear Parking Assistant System. It has a supersonic sensor which radiates supersonic to rear side of the vehicle to detect supersonic reflected from an obstacle. It consist of 4 sensor and calculates distances between vehicle and obstacle if it detects reflected supersonic. BCM receive the signal of calculated distances by LIN communication. It warns being obstacle to drivers through buzzer or displaying on cluster according to distance from obstacle. Warning level is divided into 3 step (warning level rises progressively according to distance from obstacle)