Passengers have a clear set of destinations. When you click on a person you can see where he lives, works, shops and goes for recreation. All these destinations can in theory be reached within 20 minutes by the existing means of transport. The faster your trains or busses are, the further he can get, and over time will readjust his destinations. In case that you are unable to deliver him to the requested location within the 20 min, he will “disappear”, which means he will be beamed back to his home from where he will start another journey.