GTFS-ride
https://www.transitwiki.org/TransitWiki/index.php?title=GTFS-ride&veaction=editGTFS-ride is a feed specification that allows public transportation agencies to describe and assess service consumption. GTFS-ride has arisen as a necessary complement to GTFS and GTFS-RT, which describe the kinds of service provided by a transit agency. The Oregon Department of Transportation is funding GTFS-ride specifications to describe occupancy, boarding, and alighting per stop. This will create a standards-compliant data stream for analyzing transit usage. This data is also a prerequisite for assessing transit-corridor person delay, a metric which can be used to prioritize investments in Bus Rapid Transit projects.
More on GTFS-ride can be found at www.gtfs-ride.org