References

The Columbia Electronic Encyclopedia. (1999). Coal. From Bartleby.com (http://www.bartleby.com/65) Columbia University Press. New York, NY.

Federal Highway Administration (FHWA). (2002a). Highway Statistics 2001. Office of Highway Policy Information, Federal Highway Administration. Washington, D.C. http://www.fhwa.dot.gov/ohim/hs01

Federal Highway Administration (FHWA). (2002b). National Transportation Statistics 2001. BTS02-06. Bureau of Transportation Statistics, Federal Highway Administration. Washington, D.C. http://www.bts.gov/publications/nts/index.html

United States Department of Transportation (USDOT). (2000). Comprehensive Truck Size and Weight Study. United States Department of Transportation. Washington, D.C. http://www.fhwa.dot.gov/reports/tswstudy/index.htm