A town used a simple model to estimate how long buses would take to reach the central station. The model combined route length, average traffic speed, and the usual time spent at stops. It did not explain the mechanical behavior of each engine, nor did it predict every accident. Even so, it helped dispatchers compare ordinary routes and adjust departure times. Dispatchers checked predicted times against actual arrivals and revised the averages when a route changed permanently. When a road closed unexpectedly, the estimate became less reliable, so the town added a separate warning rather than abandoning the model. The warning showed riders that the ordinary estimate no longer covered the current condition. The case shows that a model can be useful without describing every lower-level process, provided that its assumptions and limits remain visible.