private void Start()
 {
     car = GetComponent <CarScript>();
     GameObject[] allCars = GameObject.FindGameObjectsWithTag("Car");
     foreach (GameObject car in allCars)
     {
         if (car != this.gameObject)
         {
             cars.Add(car.GetComponent <CarScript>());
         }
     }
     mainTree = GetComponent <MainTreeScript>();
 }