Talk:Train routing

From OpenStreetMap Wiki
Jump to: navigation, search

Is this usable without timetable?

Is this usable without timetable, or at least general frequency, information? As an example, the Gospel Oak-Barking Line is 2tph and thus should be avoided compared to other more frequent railways. Are there external timetable sources we could use? Morwen 10:42, 9 November 2007 (UTC)
Is that information that we could easily add? e.g. anyone who lives in Weybridge could tell you without looking that there are 4 trains per hour, and list the stations you can get to on that line.
Added discussion below on the various 'levels' of routing fidelity Ojw
I agree with Morwen here, there's no use in doing "routing" with public transport networks without timetables. You can't travel on a railway line without a train being there. Any route that uses frequency of trains can only give you a "most likely" quickest route between two stations, but if the suggested route has a couple of changes of train along the way, then the "cost" of missing that connecting train will be relatively large. E.g. if you miss a train at a connecting station and end up with a half-hour wait for the next one, you could have been 30-50 miles further up the track if you'd stayed on the train - and could maybe have caught another train on a different line which gets you to your destination much quicker. If there are connecting trains, then only a timetabled solution is likely to have any value for a train traveller. Richard B 13:45, 12 November 2007 (UTC)
In your case of connecting trains (arguably a very complex case to start with) then you can calculate the expected and worst-case waiting times based on the frequency of trains. And if any trains are delayed, then that approach is better (less brittle) than one which uses a timetable. This is the algorithm used by london underground travellers (when did you last go for a specific train on the bakerloo line? do they even have timetables?) Ojw 19:20, 14 November 2007 (UTC)
I wasn't necessarily thinking of something like the London Underground - with very frequent trains on a dense network. I was thinking more of Network Rail type routes - and potentially long distances between start location and finish location. I wouldn't exactly say a route involving more than one train was exactly an atypical request for someone planning a journey. When you type in a route, you expect to be shown the optimal quickest, perhaps with certain restrictions based on cost etc. If you are told by the router to disembark at a station where there isn't a scheduled service for the next half-hour, your time *could* have been better spent travelling to a different station further along the line which perhaps did have a service taking you to your eventual destination more rapidly. You can go quite a long way in half an hour on some trains - particularly on things like Intercities which stop at several hub-stations along the way. Richard B 01:14, 15 November 2007 (UTC)