Nowadays, the vehicle’s accident occurring rate is high in Malaysia especially during the period of festival celebrations. Thus, it is necessary to develop a low cost and high effectiveness collision avoidance system that is affordable for every vehicles. Therefore, this research focus on to design and model a collision avoidance system that can slow down when approaching obstacles. The effectiveness of this collision avoidance system is evaluated based on its effectiveness of slowing down when it is approaching obstacles as well as when there is sudden obstacles appear in front of it. In this research, the collision avoidance system will be tested on a modelling car that is built with robot car chassis. The Arduino Nano is the controller for this system while there are ultrasonic sensor and encoder sensors to detect the obstacle distance and speed of the wheel respectively. The Arduino board will be programmed with PID control algorithm to allow the modelling car to slow down when approaching obstacle and stop before colliding with the obstacles. According to the result obtained, the most suitable PID constants for this collision avoidance system is Kp = 0.7, Ki = 0.7 and Kd = 0.07. The collision avoidance system is sensitive to sudden obstacle as it can stop the modelling car in just 0.3 second when the sensor detect sudden obstacle. To conclude, this collision avoidance system can slow down and prevent the modelling car crashing to the front obstacle while ensuring the safety and comfortable of the passengers.