|Highway||Rail||Transit Rail||Navigable waterways||Pipeline|
|Class I||Amtrak||Commuter rail||Heavy rail||Light rail||Hazardous liquid||Gas|
NOTES: Highway includes all public road and street mileage in the 50 states and the District of Columbia. Beginning in 1998, approximately 43,000 miles of Bureau of Land Management Roads are excluded. Class I rail data represent miles of road owned (aggregate length of road, excluding yard tracks, sidings, and parallel lines). Portions of Class I freight railroads, Amtrak, and commuter rail networks share common trackage. Amtrakdata represent nondirectional route-miles operated. Some Amtrak service is operated on the right-of-way owned by Amtrak, but the majority of route miles are on right-of-way owned by Class I Freight railroads or commuter rail networks. Transit system length is measured in directional route-miles. Directional route-miles is the distance in each direction over which public transportation vehicles travel while in revenue service. Directional route-miles are computed with regard to direction of service, but without regard to the number of traffic lanes or rail tracks existing in the right-of-way. Beginning in 2002, directional route-mileage data for the commuter and light rail modes include purchased transportation.
Navigable waterways are estimated sums of all domestic waterways, which include rivers, bays, channels, and the inner route of the Southeast Alaskan Islands, but does not include the Great Lakes or deep ocean traffic. The Waterborne Commerce Statistics Center considers 12,000 miles as commercially significant inland shallow-draft waterways in 2007. Hazardous liquid pipeline includes trunk and gathering lines for crude-oil pipeline. Gas pipeline mileage includes transmission, gathering, and distribution.
SOURCES: Highway: Federal Highway Administration, Rail: Association of American Railroads and Amtrak, Transit: Federal Transit Administration, Navigable Waterways: U.S. Army Corps of Engineers, Pipeline: Office of Pipeline Safety and American Gas Association as cited in U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, National Transportation Statistics, table 1-1, available at http://www.bts.gov/publications/national_transportation_statistics as of January 2009.