A data frame of monthly NTD data with the requested ntd_variable in the `value` column
Arguments
agency
Name of the transit agency to retrieve. Defaults to `all` agencies
data_type
Type of NTD data. Either "raw" for data released without adjustments or "adjusted" for data with adjustments and estimates
ntd_variable
Which variable to return. `UPT` for unlinked passenger trips, `VRM` for vehicle revenue miles, `VRH` for vehicle revenue hours, or `VOMS` for vehicles operated in maximum service.
modes
Transit mode to retrieve. Common modes include `MB` (bus), `CR` (commuter rail), `HR` (heavy rail), `LR` (light rail). Defaults to `all` modes.