Racing Game - help me actionscript blockades!

[king_of_turtles2002]

I need help! I need walls for the game i am creating. The cars can go right off the track! Here is the game file: http://www.1matthew.com/flash/game.rar And here is the actionscript for the car, any help would be great!:


onClipEvent(load){
accel = .2
deccel = .95
steer = .02
MINspd = -5
MAXspd = 6
}

onClipEvent(enterFrame){
if (LR = Key.isDown(Key.RIGHT)-Key.isDown(Key.LEFT)) angle += LR*steer*speed
if (UD = Key.isDown(Key.UP)-Key.isDown(Key.DOWN)) speed = Math.min(Math.max(speed+UD*accel,MINspd),MAXspd)
else speed *= deccel

_rotation = angle*180/Math.PI
_x += Math.cos(angle)*speed
_y += Math.sin(angle)*speed
if (_y<0) {
_y = 400;
}
if (_y>400) {
_y = 0;
}
if (_x<0) {
_x = 600;
}
if (_x>600) {
_x = 0;
}
}

[Runes_Tooth]

Go here.

He has plenty of tutorials on how to do hitTests, which is what you would do to keep the car on the track.