Hi Jonathan, thanks for those details. To clarify, the "Activity" resource in your screenshot is unrelated to ridership data: it is a property of an Alert (representing a disruption in service) that lets us inform riders what actions will be affected by the disruption. For example, if an escalator breaks down, we can publish an Alert that indicates the USING_ESCALATOR activity is affected at the relevant station.
In general you will not find anything related to ridership data in the V3 API or GTFS, as these are focused on providing data about MBTA service itself such as schedules, maps, and real-time predictions. We do publish historical ridership data on the MBTA Open Data Portal
. If you need more recent data than what is there, you may want to reach out directly to the Office of Performance Management and Innovation (OPMI) at op...@mbta.com