How to make a startline and finishline? I'm making a car game. Help me.!!

I have a simple carController script. I want to display some UI text like ready steady go! and when go text is display and gone. Player car and AI car can run. And when cars reached the finishline car automatically stopped running. How to do it.

//CarController1.js var wheels : Transform[];

var enginePower=150.0;

var power=0.0; var brake=0.0; var steer=0.0;

var maxSteer=25.0;

function Start(){ rigidbody.centerOfMass=Vector3(0,-0.5,0.3); }

function Update () { power=Input.GetAxis("Vertical") enginePower Time.deltaTime 250.0; steer=Input.GetAxis("Horizontal") maxSteer; brake=Input.GetKey("space") ? rigidbody.mass * 0.1: 0.0;

 GetCollider(0).steerAngle=steer;
 GetCollider(1).steerAngle=steer;
   
 if(brake > 0.0){
     GetCollider(0).brakeTorque=brake;
     GetCollider(1).brakeTorque=brake;
     GetCollider(2).brakeTorque=brake;
     GetCollider(3).brakeTorque=brake;
     GetCollider(2).motorTorque=0.0;
     GetCollider(3).motorTorque=0.0;
 } else {
     GetCollider(0).brakeTorque=0;
     GetCollider(1).brakeTorque=0;
     GetCollider(2).brakeTorque=0;
     GetCollider(3).brakeTorque=0;
     GetCollider(2).motorTorque=power;
     GetCollider(3).motorTorque=power;
 }

}

function GetCollider(n : int) : WheelCollider{ return wheels[n].gameObject.GetComponent(WheelCollider); }