Ambulance GoGoGo (car exit) description

There was an accident around the busy street. The ambulance was there but can hardly get out of the traffic jam. Can you help?
There is only one simple rule, each car can only move back and forth.
There is only one simple goal, get the ambulance to the exit.
Easy? Could be tricky enough for you!
4 difficulties, 2000 levels, months of fun. Get it now!