small racing game

Hi.
I am working on a small project and I tried to implement a collision detection, which doesn't really works how it is supposed to do. When I hit the other car the accident happens, but when I steer to the left or the right Alice crashes and I don't know why. I checked the code a few times already, but I can't find the bug. In addition for a strange reason I can't make the program say, that you win, when I am close to the box on the road (will be used as an invisible finish line).
All in all this game is not awesome, but first I wanted to see, if I could manage the main parts like the collision detection. Unfortunately I don't know an answer to my problem and it would be great if someone can help me find this bug or just upload