Allow for selection of particular mode(s)

[jamesbiagioni]

It would be nice to have a way to select particular modes, perhaps using the required "route_type" parameter in the GTFS spec.

This way, for example, if I have a graph DB with road, bus and train network data, I would be able to generate a walking-only route, or a route that uses walking and trains but no buses. This would be useful for allowing user-preference to come into play.

Reference: http://groups.google.com/group/graphserver/browse_thread/thread/7a779082f0561c57