Top down car game collision question

[chuckylefrek]

I am making a top down view car game and could do with some advice on collision detection. I have read numerous posts about these types of games but havent seen anything specific to my question.

I can detect the collisions no problem. The problem I am having is determining how far the car can move to just before the collision.

To detect collisions I am using 5 points around the center of the car and using hitTest(x, y, true) function. I calculate the position of the points if the car moved at its current speed. If a collision is detected at this new position, I only want to move the car enough so it just reaches the collision point.

The track is quite irregular shaped so I am not sure how best to calculate how far the car can move so it just gets to the edge of the track.


Here is the basic code for detection of a collision with one of these points

Whils

var frontX = car_mc.front._x;
var frontY = car_mc.front._y;
		
car_mc.frontNode = {x:frontX, y:frontY}
		
car_mc.localToGlobal(car_mc.frontNode);
		
var newFrontX = car_mc.frontNode.x + speedX;
var newFrontY = car_mc.frontNode.y + speedY;
		
if (terrain.hitTest(newFrontX, newFrontY, true)){ 
		
	hitStateTxt.text = "HIT"
			
			
} else {
			
	hitStateTxt.text = "SAFE"

        // No collision so move normally
			
	car_mc._x += speedX;
	car_mc._y += speedY;

}

Any advice much appreciated. If there is a better way of doing collision detection on this type of game, I would be most interested to hear about it. Btw I am creating this game in Flash 8 with AS2.

Paul