OTM
OpenTripModel is a data model for exchanging real-time logistical travel data on the web.
The OTM format and its description can be found on the website: https://otm5.opentripmodel.org.
There is also a developer portal available from OTM with information about the standard: OTMv5 Developer.
Product Types in OTM
The following product types are available in OTM format: