Service delineation in GTFS-Flex

This issue relates to the GTFS-Flex proposal, and is opened following a series of roundtable discussion to resolve the outstanding issues with the proposal. These discussions were hosted by MobilityData and attended by various stakeholders within the GTFS community.

You can find the GTFS-Flex proposal here: [https://github.com/MobilityData/gtfs-flex/blob/master/spec/reference.md](https://github.com/MobilityData/gtfs-flex/blob/master/spec/reference.md)

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With GTFS-Flex, the specification is no longer limited to fixed route services. It will be possible to have different transit services represented in a single GTFS file.

Therefore, there is a need to delineate which types of services are represented in a GTFS dataset. We propose these four options:

- Fixed route service
- On-demand service
- Deviated fixed route service
- Hybrid service (combination of the above services that varies by time such as a fixed route accepts deviation requests during off-peak hours only)

To avoid the complexities of adding new fields to GTFS, we are proposing a process to parse the files and fields in GTFS to determine the type of services represented in the dataset.

This is the link to the flowchart: [GTFS-Flex Decision Tree](https://docs.google.com/drawings/d/12FIdBqJEE-h6B1sJ0lyIq_eCTkLwWYTIhDtLN3j8L9c/edit)

Please provide your feedback on the process here - as well as your thoughts on where this diagram should live. We propose having it in the [GTFS Schedule Best Practices page](https://gtfs.org/schedule/best-practices/).