如何在AS3中创建汽车碰撞？

I have a background with a top view motorway and forest on the sides and I want it so that when the car touches the green forest area the game changes to another scene. I have tried to put a line on the forest area and make it so that if the car hits the line switch to another scene but I have failed. I'm using action scrip 3. Thanks.I have a background with a top view motorway an