|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. Amtrak data represent miles of road operated. 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 monitored 12,612 miles as commercially significant inland shallow-draft waterways in 2001. Hazardous liquid pipeline includes trunk and gathering lines for crude-oil pipeline. Gas pipeline mileage includes transmission, gathering, and distribution.
SOURCES: Various sources, as cited in U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, National Transportation Statistics 2007, table 1-1, available at http://www.bts.gov/ as of April 2007.