GTFS Diff aims at providing a universal and unified way to list differences between two GTFS files. It is designed to be easily understandable by humans, but also easily produced and processed by computers.

transport.data.gouv.fr is the French National Access Point for mobility data. It is operated by the French Ministry of Transportation. The platform gives access to a variety of mobility data, including a number of GTFS files.

It happens frequently that companies or individuals using this data modify it. For example to correct spelling mistakes in a stop name, add color to routes or wheelchair information.

Every time a GTFS file is updated by the producer with a recent schedule, those corrections need to be applied again. We lack a universal way to list a series of modifications with the corresponding explanations about the change.

It also happens that data users share their enhanced GTFS file on our platform. We then lack a way to easily understand the changes they made. If two users share their own modified version of a GTFS, we lack a way to merge their respective changes into a single file.

It is also hard for reusers to review the changes made to a given GTFS file by its official producer, making it harder to understand the impact of the changes on their systems.

• the GTFS Diff specification
• Online tool to generate a GTFS Diff on transport.data.gouv.fr
• Source code of the implementation (in Elixir)

This project was initially created by the French National Access Point to ease communication between data producers and reusers and to monitor changes made by data producers over time in their GTFS feeds.

In June 2023, MobilityData and the French NAP announced a partnership to maintain and further improve the GTFS Diff specification.