Urban rail includes heavy rail, commuter rail, light rail, streetcar rail, and hybrid rail. The Federal Highway Administration estimates monthly transit ridership, released as part of the National Transit Database. Ridership estimates have been adjusted to account for changes in data collection over time. Starting in January 2012, data for Small System Waiver agencies that do not have a mode are reported under motor bus. Data reported under hybrid rail are reported under their classifications prior to January 2012.