GTFS has extensions that add specialized functionality to the core specification. Extensions that are currently in development can be found on the changes page
Some GTFS producers have added extensions to GTFS that have not been formally adopted into the specification. Some of the major unofficial extensions are listed below.
- Google - Provides translation support, extends route types, allows for more detailed transfer rules and adds a number of other functions.
- MTC GTFS+ - Created by the San Francisco Bay Area Metropolitan Transportation Commission. Adds additional real time information, directions, rider categories and more.
- MBTA - Adds on-time performance tracking checkpoints, station and facility information and more.