Realtime feeds with data about the past

Real-time Public Transport
1

I’ve been scratching through a number of feeds, all buses so far, and have noticed that the stop_time_update entries are usually only for future stops, but not always, so I’d like to understand what’s happening.

  1. Is it safe to assume that a stop time update with arrival/departure time that is less than the trip update timestamp is an event that has happened in the past? i.e. that the bus has arrived / departed?

  2. Under what conditions are stop_time_updates omitted from the updates? For the most part it appears that any past data is omitted, is that a fair assumption? I’m thinking not, as I’ve found some records that contradict this, but I’d like to understand if they accurately reflect past data, or if they’re erroneous.

  3. There are updates with schedule_relationship: NO_DATA for each stop, and missing the trip update timestamp. The spec seems to state that NO_DATA should reflect partial updates (e.g. the next 3 stops of 10) but these are full updates. When making assertions such as “this bus is on time”, should these records be ignored?

2

Hi Mark

I have a couple of answers…

We are aware there are a few errors in the feed and are working to resolve them (so keep feedback coming!). It is incorrectly displaying some stoptime updates in the past.

  1. and 2. Yes a stoptime update prior to the trip update would indicate it was an actual, but these should not be published and will be removed in future releases of the feed.
  1. The NO_DATA are used to display timetable data when no real time tracking data is available for that Trip.

Hope that helps!