I travel in Germany fairly frequently, often using long distance trains. When I book online I have to decide whether to pay for a reserved seat. DB Navigator has a feature which predicts how busy the service is. I'd like to rely on that as a guide whether to reserve. However when I last travelled between Dresden and Berlin, the prediction was "really busy". The reality was "almost empty coach". I've had the same problem before. Is there any way to second guess the reality better than DB does?