Abstract – The increase of population produces an increase of the number of automobiles on the road, which generates heavy traffic in the streets and that causes many problems for the Citizens and traffic policemen an additional two emergency cases therefore it’s important with development technology of embedded systems to solve this problem. In this paper new traffic light controller was built to optimization using the Arduino UNO microcontroller board. The system tries to reduce traffic jams, caused by traffic lights, as possible. The system is based on microcontroller, which represent the brain of the system. The system contains ultrasonic sensors on the side of the roads. Also the system contains switches to control the traffic light manually. The ultrasonic sensor system gets activated when vehicles go along the road against it. Microcontroller controls the traffic light by driver circuit using the sensor network to determine the level of jam in the road. Different ranges of traffic light delay time intervals according to jam level are configured by microcontroller and updated regularly. In this paper the effects of temperature and humidity on the system were studied. The jam level displayer tool is another feature added to a system controlled by the microcontroller which is a traffic sign informs the drivers about the level of jam before reaching the road.