random directions

i was making a quick thing where you could use the arrow keys to drive a car around in an arena and wanted to add in other cars that moved around randomly which you could crash into.
i managed to program the player car,

code:

---

onClipEvent (enterFrame) {

	if (Key.isDown(Key.UP)) {

		speed += 2;

	} else {

		if (Key.isDown(Key.DOWN)) {

			speed -= 1;

		} else {

			speed *= .9;

		}

	}

	if (Math.abs(speed)>25) {

		speed *= .6;

	}

	if (Key.isDown(Key.LEFT)) {

		_rotation -= speed;

	}

	if (Key.isDown(Key.RIGHT)) {

		_rotation += speed;

	}

	speed *= .9;

	x = Math.sin(_rotation*(Math.PI/180))*speed;

	y = Math.cos(_rotation*(Math.PI/180))*speed*-1;

	if (!_root.land.hitTest(_x+x, _y+y, true)) {

		_x += x;

		_y += y;

	} else {

		speed *= -.5;

	}

}

---

but i cant program the computer car to move randomly based upon the same physics.
working with flash 5, please help

Here's one way to do it. This uses a random number from 0-4. If 1,2,3,4 the computer is presing an arrow key, and if 0, the computer is doing nothing.

code:

---

onClipEvent (enterFrame) {

  // change action every second

  if (lastActionTime == undefined or getTimer() - lastActionTime > 1000)

  {

    lastActionTime = getTimer();

    action = random(5) + 1;

  }



        if (action == 1) {

                speed += 2;

        } else {

                if (action == 2) {

                        speed -= 1;

                } else {

                        speed *= .9;

                }

        }

        if (Math.abs(speed)>25) {

                speed *= .6;

        }

        if (action == 3) { // left

                _rotation -= speed;

        }

        if (action == 4)) { // right

                _rotation += speed;

        }

        speed *= .9;

        x = Math.sin(_rotation*(Math.PI/180))*speed;

        y = Math.cos(_rotation*(Math.PI/180))*speed*-1;

        if (!_root.land.hitTest(_x+x, _y+y, true)) {

                _x += x;

                _y += y;

        } else {

                speed *= -.5;

        }

}

---