US Department of Transportation: Bureau of Transportation Statistics (BTS) [website] [open html - 57KB]
"As the independent statistical agency within the Department of Transportation (D0T), the Bureau of Transportation Statistics (BTS) is a politically objective supplier of trusted and statistically-sound baseline, contextual, and trend information used to shape transportation policy, investments, and research across the US and abroad. BTS is the preeminent source of statistics on commercial aviation, multimodal freight, and transportation economics. The Bureau's National Transportation Library is the permanent, publicly accessible home for research publications from throughout the transportation community, the gateway to all DOT data, and the help line for the Congress, researchers, and the public for information about transportation. The BTS Director is by law the senior advisor to the Secretary on data and statistics."