GTFSrealtime

GTFS Realtime, also written as GTFS-RealTime or GTFS-RT, is an extension to the General Transit Feed Specification (GTFS) that provides real-time information about public transit services. It is designed to complement static GTFS schedule data by delivering live updates such as trip progress, vehicle locations, and service advisories. The data are encoded using Protocol Buffers and delivered as feeds that can be accessed by rider applications and transit systems.

The GTFS Realtime data model centers on three primary feed types: TripUpdate, VehiclePosition, and ServiceAlert. A feed message (FeedMessage) contains a header and a list of entities. TripUpdate posts changes to a scheduled trip, including estimated times at stops via StopTimeUpdate elements. VehiclePosition offers current vehicle location data (latitude, longitude, bearing, speed) and optional attributes such as occupancy. ServiceAlert conveys notices like delays, detours, or service suspensions with specified active periods. This structure allows consumers to present up-to-date journey planning, status notifications, and operational awareness.

Feeds are published by transit agencies through HTTP(S) endpoints and consumed by mobile apps, websites, and internal systems. The protobuf encoding ensures compact, efficient transmission, and a JSON representation is available in some implementations. The static GTFS feed remains the source of truth for schedules; GTFS Realtime adds dynamic information to support real-time routing, alerts, and passenger information.

The specification is maintained by a community of developers and transit agencies, with involvement from Google, and has been adopted by many transit agencies worldwide as a standard method for sharing real-time transit data.