We all know that traffic signals help us to to get to our destination safely. That is why; they are there in the first place, but traffic signals won't help if you don't know their meaning in the first place. For a driver, knowing traffic signal is a necessity on the road because they guide us to safety.
The idea here is to guide the cars safely to their destination. You need to click the arrow to where you want them to go. There is a required number of vehicles that you need to send to their destination. Each car is differentiated by means of their color. If you send a car on the wrong direction then that will add to the number of cars that you need to send to their destination.