The basic GTFS format contains only static (i.e., infrequently changing) transit information such as schedules, routes, and bus stops. Therefore, a GTFS dataset alone will not enable real-time transit information services for a transit agency. However, for many real-time applications GTFS data is also required to describe basic information about the transit system. GTFS-realtime  and SIRI  are emerging formats implemented by a number of agencies for real-time transit data such as estimated arrival times based on real-time vehicle positions. Although real-time transit data formats are outside the scope of this paper, several applications are presented below for real-time transit information that require the basic GTFS dataset in addition to another real-time information source. These applications aren’t usable without the basic GTFS dataset, so GTFS plays an important role in these applications.
- OneBusAway - An open-source software system for real-time transit information.
- NextBus - A vendor that provides real-time information service for many transit agencies in the United States.
- TransLōc - A vendor that provides real-time information and visualization for transit and shuttle systems.
- Google, Inc. "What is GTFS-realtime?". Accessed August 1, 2012 from https://developers.google.com/transit/gtfs-realtime/
- European Committee for Standardization (CEN). "CEN/TS 15531 (prCEN/TS-OO278181 ) SIRI Home Page." Accessed August 1, 2012 from http://www.kizoom.com/standards/siri/