As a traffic police officer, it is your job to ensure that there will be no accidents in your area. If some acidents do happened, you can bet on it that you will lose your job. You need to stay in the middle of the road and tell the drivers what to do or ese, you will lose your job.
In this game, that is what you need to do. Click on the car to let it run fast or to slow it down. There will be some accidents if you are just going to let them be. You must take control or you will see some cars coliding with othe vehicles.