The US Department of Transportation's Bureau of Transportation Statistics provides Transportation Statistics Annual Report (TSAR), a companion to NTS, in Adobe Acrobat (.pdf) format, from 1994 to the present at this time. Transportation in the United States: A Review, summarizing these four reports, is also available.
Released in July 2002, this 431-page document prepared by the United States Bureau of Transportation Statistics contains almost every piece of aggregate data on transportation imaginable. While going through the entire document may be a challenge, the report is divided into more readily digestible sections such as Transportation System, Transportation Safety, and Transportation and the Economy....