Car smashing through crowd- Collision issue.

Hey guys! I've got a car to launch into a crowd. Currently it hits robots and they tumble and die when hit. I need the car to continue through the crowd without stopping and smash into a wall. Car contacting robots should cause ROBOTS to die. Car contacting wall should cause CAR to die.

I'm currently using OnCollisionEnter with code to kill the robots and car on impact. If car is not killed with code, it just bounces around level after hitting robot.

What would be the best way to use either OnCollisionEnter or OnTriggerEnter with seperate tags for "Enemy" and "Wall" to dictate end results?

I'm using JavaScript too, Thanks for any advice.

Main code block attached to EnemyRobot:

function OnCollisionEnter (collisionInfo : Collision) 
// Used if we were hit by a CAR on left or right side...
{  
    var hitDir : Vector3 = collisionInfo.contacts[0].point - transform.position;
    var left : Vector3 = transform.TransformDirection( Vector3.left ); 
    //var right : Vector3 = transform.TransformDirection( Vector3.right ); 
    if( Vector3.Dot( left, hitDir ) > 0)
    {    
        TumbleRight();
        Debug.Log("HitLeft");
        //We were hit on the Left, Play the TUMBLE RIGHT animation
    }  
    else  
    {    
        TumbleLeft();
        Debug.Log("HitRight");
        //We were hit on the Right, Play the TUMBLE LEFT animation
    }  
}

Main code block attaced to Car:

function OnCollisionEnter (collision : Collision) 
{
    // Instantiate explosion at the impact point and rotate the explosion
    // so that the y-axis faces along the surface normal
    var contact : ContactPoint = collision.contacts[0];
    var rotation = Quaternion.FromToRotation(Vector3.up, contact.normal);
    Instantiate (explosion, contact.point, rotation);

    // And kill our selves
    Kill ();    
}

You can try increasing the car's rigidbody mass and lowering the robot's mass, this will stop your car flying around and make the robots fly away faster