a Regular route intercity service.
b Prior to 1984, excludes commuter railroad, automated guideway, urban ferryboat, demand response, and most rural and smaller systems.
c Amtrak began operations in 1971.
KEY: R = revised; U = data are not available.
SOURCES: See Table 2-15a for data sources.
NOTE: BTS converted current dollars to chained dollars using a combination of deflators constructed from the Bureau of Labor Statistics' Consumer Price Index and the Bureau of Economic Analysis' chain-type price index.