private void Update()
    {
        if (activate_car)
        {
            //Give the car a score besed on its local Z velocity and distance from the walls.
            car_score += body.gameObject.transform.InverseTransformDirection(body.velocity).z *Time.deltaTime;

            if (car_ai)
            {
                car_ai.GetNetwork().SetNetworkScore(car_score);
            }
        }
    }