FixedJoint

I make transporter car gamei have 6 gameobjects(cars) with tag Player how can i do that any gameobject(car) enter to the collision(transporter) and when it enter create FixedJoint to object(car and transpoorter)??

using UnityEngine; using System.Collections;

public class Enter : MonoBehaviour {

 public Transform Group1;
 // Use this for initialization
 void Start () {
 
 }
 
 // Update is called once per frame
 void Update () {
 
 }
 void OnCollisionEnter(Collision collision)
 {
     if(collision.gameObject.tag=="Player")
     { 
         collision.transform.parent = Group1;
         if(collision.rigidbody != null)
         {
             var joint = gameObject.AddComponent<FixedJoint>();
             joint.connectedBody = Group1.rigidbody;

         }
     }
 }

}