support GTFS-ServiceChanges

[derhuerst]

GTFS-ServiceChanges v3.1 has several new features:

• GTFS-TripUpdates v3 extends GTFS-TripUpdates to change values on a trip object, either by directly providing the new values (e.g. new trip headsign or new trip short name) or by referencing another entity already defined in the (CSV) GTFS (e.g. a shape, a route, or platform). The only limitations being that no stop time can be added, and all stop_id and stop_sequence pairings in the TripUpdate must match the same GTFS static trip (it is allowed to have SKIPPED stops within a TripUpdate, as the stop_sequence for the stops do not change).
• GTFS-NewTrips allows defining completely new trips in real-time, which is useful for replacement shuttles, unplanned event-specific shuttles, or detours that change the stop_sequences of a trip.
• GTFS-NewShapes allows adding new shapes in real-time, which is useful, for example, when a road is closed and therefore the path of the vehicle won’t be the same as planned, or when a trip is shortened by having an early terminus.
• GTFS-NewRoutes allows adding new routes in real-time, which is useful, for example, when a bus replacement shuttle does the same trip as the service it’s replacing, but with a bus.
• GTFS-NewStops allows adding new stops in real-time, which is useful when a bus replacement shuttle stops at a street corner without bus stop, or when a stop is moved for unplanned reason (e.g. demonstration, road accident, emergency work). GTFS-NewStops must be used with GTFS-NewTrips - new stops cannot be used in TripUpdates.
• GTFS-ServiceUpdates allows activating or deactivating service in real-time, which is useful for disabling or enabling many trips at the same time, such as planned services for unexpected occasions (e.g: snow bus routes, light-rail diversion in case of demonstration downtown).