How to follow buses and trains live

Live: the agency publishes where each vehicle is, from the vehicle’s own GPS, usually as a GTFS Realtime feed. This is most of what you see. TAKIP reads about 750 such feeds in about 40 countries, plus a few agencies’ own APIs.

Estimated: some systems, often metros running underground where GPS doesn’t reach, publish only when each train will reach its next stations. TAKIP puts such a train between the station it left and the one it is heading to, as far along as those times say. The London Underground is placed this way, from TfL’s arrival predictions. A few systems publish positions they work out themselves from the timetable and live delays; those are marked estimated too.

Scheduled: where a system publishes nothing live at all, as on the Istanbul and İzmir metros, trains run from the published timetable, each one where its timetable says it should be now. That is a planned service, not a sighting, and the map labels it so.

Vehicles appear from zoom 10, about a city at a time. Zoomed out, each city with transit data gets a ring, larger where more vehicles run; click one to fly in.

Trains, trams, metros and cable cars are blue; buses, ferries and the rest are sandy yellow. A filled marker is a GPS position. A hollow one was placed from its stops or its timetable, and timetable trains are drawn fainter still. Anything the feed hasn’t updated for five minutes fades, since it may have moved on.

From zoom 13 each marker gets a notch pointing the way it is heading, where the feed says, and from zoom 14 short route numbers are written beside them. The layer refreshes every 20 seconds while you are zoomed in.

While a vehicle’s card is open, TAKIP checks it every 10 seconds, at any zoom and even with the layer switched off. Between updates it glides along its route rather than jumping, and leaves a trail behind it.

Coverage follows open data. The United States, Canada and France have the most feeds; elsewhere it depends on whether each operator publishes. A city can have its trains on the map but not its buses, or the other way round.

Each city the layer covers has a page of its own at /city/<place>/transit, such as /city/cincinnati/transit, naming its operators, how each one’s vehicles reach the map, and what is running there now.