Real time¶
Real-time data has a single source — the driver's device — and two outlets: supervision on the operator's side, and passenger information on the public side.
The chain, from vehicle to passenger¶
- The driver's device reports its position and the progress of the trip it is operating.
- The API derives the actual progress from it: stops served, delay, position along the shape.
- Those elements feed the standardised feeds consumed by journey planners and displays.
Each step is readable in the API, but not in the same place nor with the same freshness: a vehicle's position is queried as of now, whereas the trace of what happened is read from history.
No device, no real time¶
This is the dependency to remember: a trip whose device is not in service is not tracked. It stays scheduled in the reference, but no actual data concerns it — no position, no delay, no passing at stops.
The device knows the trip it is operating at a given moment, designated by the triplet described on the previous page. It also carries its connection state, which makes it possible to tell a stationary vehicle from one that has stopped reporting.
| Endpoint | Purpose |
|---|---|
GET /api/v4/groups/<group_id>/devices |
Lists the devices and their current state |
GET /api/v4/groups/<group_id>/devices/online |
Lists the currently connected devices |
GET /api/v4/groups/<group_id>/vehicle_movements |
Gives the movements, including outside commercial service |
What goes out to passengers¶
Two standardised formats broadcast the same network state, with two different formalisms. The choice depends on what the consumer expects, not on what Pysae prefers.
| Format | Used by | See |
|---|---|---|
| GTFS-RT | Journey planners, passenger applications | gtfs-rt |
| SIRI | European passenger information systems, transport authorities | siri |
| Endpoint | Purpose |
|---|---|
GET /api/v4/groups/<group_id>/gtfs-rt |
Gives the group's GTFS-RT feed |
GET /api/v4/groups/<group_id>/siri |
Gives the group's SIRI feed |
Those feeds are a product, not a source: they aggregate the reference, the devices' positions, the alerts and the trip updates. A discrepancy seen in a feed is therefore diagnosed by tracing back to whichever of those inputs carries it.
Disruptions¶
Two distinct objects feed the "disruption" part of the feeds, and they must not be confused:
- an alert is a message intended for passengers — works, an event, a stop not served;
- a trip update is a change to the service itself — a stop skipped, a trip diverted. In the GTFS-RT feed it is published both as a
TripUpdate(skipped stops, delay) and as aTripModificationsentity (replacement stops, modified shape).
One real disruption often gives rise to both: the service changes, and it is announced.
Next¶
Real time says what the vehicles are doing. What remains is who drives them and under which organisation — that is the subject of the Operations page.