All states, 90 mins non PROW, filter clarity

Author: schnuerle

provider/README.md

@@ -539,7 +539,9 @@ In the case that a `stop_id` query parameter is specified, the `stops` array ret
 
 ### Vehicles
 
-The `/vehicles` endpoint returns the current status of vehicles in an agency's [Jurisdiction](/general-information.md#definitions) and/or area of agency responsibility. Only vehicles that are currently in available, unavailable, or reserved states should be returned in this payload. Data in this endpoint should reconcile with data from the `/status_changes` enpdoint. 
+The `/vehicles` endpoint returns the current status of vehicles in an agency's [Jurisdiction](/general-information.md#definitions) and/or area of agency responsibility. All vehicles that are currently in any `[vehicle_state](/general-information.md#vehicle-states)` should be returned in this payload. Since all states are returned, care should be taken to filter out states not in the [PROW](/general-information.md#definitions) if doing vehicle counts. For the states `elsewhere` and `removed` which include vehicles not in the [PROW](/general-information.md#definitions) but provide some operational clarity for agencies, these must only persist in the feed for 90 minutes before being removed. 
+
+Data in this endpoint should reconcile with data from the historic `[/status_changes](/provider#status-changes)` enpdoint, though `/status_changes` is the source of truth if there are discrepancies. 
 
 As with other MDS APIs, `/vehicles` is intended for use by regulators, not by the general public. `/vehicles` can be deployed by providers as a standalone MDS endpoint for agencies without requiring the use of other endpoints, due to the [modularity](/README.md#modularity) of MDS. See our [MDS Vehicles Guide](https://github.com/openmobilityfoundation/mobility-data-specification/wiki/MDS-Vehicles) for how this compares to GBFS `/free_bike_status`. Note that using authenticated `/vehicles` does not replace the role of a public [GBFS][gbfs] feed in enabling consumer-facing applications.