Rollbar physics hanlder so that physically driven cars don;t flip over. use as componeennt

AntiRollBar.cs

//http://answers.unity3d.com/questions/21417/my-car-keeps-fliping-over-i-have-an-idea-how-to-fi.html 
 
 using UnityEngine;
 using System.Collections;
 
 
 public class AntiRollBar : MonoBehaviour {
 public WheelCollider wheelL;
     public WheelCollider wheelR;
     public float antiRollVal = 5000f;
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         WheelHit hit;
         float travelL=1.0f;
         float travelR=1.0f;
         bool groundedL = wheelL.GetGroundHit(out hit);
         if (groundedL){
                 travelL = (-wheelL.transform.InverseTransformPoint(hit.point).y - wheelL.radius) / wheelL.suspensionDistance;
         }
         bool groundedR = wheelR.GetGroundHit(out hit);
         if (groundedR){
                  travelR = (-wheelR.transform.InverseTransformPoint(hit.point).y - wheelR.radius) / wheelR.suspensionDistance;
 
  
         }
         
     float antiRollForce = (travelL - travelR) * antiRollVal;
 
  
 
     if (groundedL)
 
         rigidbody.AddForceAtPosition(wheelL.transform.up * -antiRollForce,
 
                wheelL.transform.position);  
 
     if (groundedR)
 
         rigidbody.AddForceAtPosition(wheelR.transform.up * antiRollForce,
 
                wheelR.transform.position);  
     }
 }