Table 1. Data Sources for the Transportation Services Index (TSI),,, Mode,,Source,Measure Freight,Trucking,American Trucking Associations,Index of tonnage ,Air,Bureau of Transportation Statistics and carrier websites,Freight ton-miles ,Rail ,Association of American Railroads,Carloads & Intermodal units ,,Federal Railroad Administration (FRA),Quarterly ton-miles ,Water,U.S. Army Corps of Engineers,Tons ,Pipeline,Energy Information Administration,"Thousands of barrels, billion cubic feet" Passenger,Air,Bureau of Transportation Statistics and carrier websites,Revenue passenger-miles ,Rail,Federal Railroad Administration,Revenue passenger-miles ,Transit,American Public Transportation Association,Unlinked trips "SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, http://www.bts.gov.",,,