Updated solution section

Rephrased the solution description.

The client application is necessary, even when we get access to railway realtime data. That data can be used to simulate passengers, but it is important that we track *people's* location and not the train position. The railway guys has fairly good knowledge of where their trains are. Keep in mind that our goal is to mine traffic patterns based on mobile applications. In addition, I think the railway realtime data can be used to filter out / exclude irrelevant data - if we know there are no train service at the user's location then the user is most likely not onboard a train. Or, say the user is at a railway but no train traffic at that time then the user is unfortunately drunk and walking at the railroad track (we can send police to pickup the guy instead :-P )

Also tried to leave out implementation details (e.g., on database, it should be common knowledge to make a basic webapp with a backend database, if not we do not have space here to teach people about that here).