How to make an AI Enemy Car in which it follows the track during the Race ?

The AI for enemy car can be done by using waypoints method..

the following code is used

var waypoint : Transform[];

var speed : float =20;

private var currentWaypoint : int;

var loop : boolean = true;

function Awake()

{waypoint[0]=transform;}

function Update ()

{ if(currentWaypoint < waypoint.Length)

{ var target : Vector3 = waypoint[currentWaypoint].position;

var moveDirection : Vector3 = target-transform.position;

var velocity = rigidbody.velocity;

if(moveDirection.magnitude<1)

{ currentWaypoint++;}

else { velocity = moveDirection.normalized * speed;  //velocity = Vector3.forward * speed; }  }

else { if(loop)  {  currentWaypoint=0; }

else   { velocity = Vector3.zero; }

} rigidbody.velocity = velocity;

}