List <string> _allGuids = new List <string>(); // The list of Guids of all the cars increased private void OnTriggerEnter(Collider other) { if (other.gameObject.layer == LayerMask.NameToLayer(_layerHitName)) // If this object is a car { CarUserControl car = other.transform.root.GetComponent <CarUserControl>(); // Get the compoent of the car string carGuid = car._guid; // Get the Unique ID of the car if (!_allGuids.Contains(carGuid)) // If we didn't increase the car before { _allGuids.Add(carGuid); // Make sure we don't increase it again car.OnCheckPoint(); // Increase the car's fitness } } }