# Feeds & Standards > GTFS, GTFS-Realtime, GTFS-Flex, GBFS, GOFS, and the specifications themselves. 6 articles in this lane on ITS Feed. Canonical: https://its-feed.com/topics/feeds-standards/ --- - [September 2026 roundup: alert images go final and an unwritten GTFS rule gets written](https://its-feed.com/articles/roundup-2026-09/): What moved on the transportation data layer from early August to early September 2026: two GTFS merges on the same day, MDS 2.1 emergency zones prototyped in Seattle, and three proposals in the queue that would change what a feed carries. (Roundup, published 2026-09-04) - [GTFS-Flex: dial-a-ride in the GTFS spec, and who actually publishes it](https://its-feed.com/articles/what-is-gtfs-flex/): GTFS-Flex has been part of the core specification since March 2024, and the validator polices it with 29 dedicated checks. We read every feed in the Mobility Database to see how many agencies actually use it. (Explainer, published 2026-08-21) - [MDS, GBFS, and CDS: the shared-mobility data stack, mapped](https://its-feed.com/articles/shared-mobility-data-stack/): Three specifications cover the same scooters, bikes, and delivery vans, and practitioners routinely pick the wrong one. Here is what each was built to answer, why MDS requires a public GBFS feed, and where the boundary between them actually falls. (Explainer, published 2026-07-31) - [What GTFS is, and how a transit feed fits together](https://its-feed.com/articles/what-is-gtfs/): GTFS is the open format that puts transit schedules into your maps app. Here is what a feed contains, how its files join together, and why it became the default for transit data worldwide. (Explainer, published 2026-07-15) - [What GTFS-Realtime is, and how a feed works](https://its-feed.com/articles/what-is-gtfs-realtime/): GTFS-Realtime is the standard for live transit data: what a feed carries, how Protocol Buffers structure it, and why the quality rests on the systems behind it. (Explainer, published 2026-07-14) - [How real-time arrival predictions actually work](https://its-feed.com/articles/how-real-time-arrival-predictions-work/): The countdown on the sign is a prediction, not a readout of a bus you can see. Here is the data chain behind it, from the vehicle's GPS to the feed the sign reads, and the three ways agencies turn location into a time. (Explainer, published 2026-06-19) --- Source: ITS Feed, https://its-feed.com/topics/feeds-standards/ ITS Feed is an independent editorial site on the data and technology layer of transportation, published by the team at Veodyn. Figures trace to the sources linked inline. Site index for agents: https://its-feed.com/llms.txt