Glossary of Google Realtime Transit terminology

This page provides a list of realtime transit terms and definitions to help transit partners and data aggregators use the terms consistently across multiple documents or user interfaces.

Carriage A separate section of a train that carries passengers.
Entity A distinguishable object that represents a real-world existence, such as a vehicle, trip, or stop. Entities are identifiable with a unique ID, and each entity type has a set of fields that describe it.
Header A record that provides metadata about a feed, such as its version and timestamp.
Message A record that contains data about a particular entity. Messages are included in feed messages, and they provide information about the entities in the feed.
Realtime feed A file that complies with the GTFS-realtime format and provides current information about the transit service. The file's contents cover trip updates, service alerts, or vehicle positions
Service alerts Alerts that provide passengers with updates when there’s a disruption on the transit network.
Trip updates Updates about the delays or cancellations of individual trips.
Vehicle positions Information about the current location of a particular vehicle.