Accidents are the third highest cause of death in the world. Through the collision avoidance system applied to smart car, it is expected that accidents on the car can be avoided and the number of accidents can be reduced. This system applies the concept Wireless Sensor Network (WSN), the type of network that can pass through the process of sensing, transmitting data, and monitoring through internet connection. The design and implementation of collision avoidance prototype in this smart car works by means of the distance between the cars obtained from the Ultrasonic HC-SR04 sensor which then becomes the Arduino Uno input to regulate the speed of the car in order to avoid a collision. Communication between cars using Xbee S2 is connected to Rapberry Pi to connect to the web server. Information gained distance and speed of the car will occur on websites that can be accessed by the user. Maximum Xbee S2 test result are 89 meters. The delay value from the sensor to the monitoring system is 0.411 second, while the average throughput value is 641.73 bytes/s. The value of benefits and realibility of the system is 96.24% and 98.08%.