The transit specification is the main technical source. It covers the transit endpoint families, request parameters, XML and JSON examples, SIRI message structures, GTFS+ files, historic feed notes, and shapes coverage.
The overview specification defines the broader 511 data-exchange context: encoding, language, authentication, throttling, discovery, jurisdictions, and other shared protocol guidance.
The data agreement defines the license, attribution expectations, branding limits, disclaimers, indemnification, and termination rules for anyone using 511-provided data.
