Source: DOT BTS.
The TSI was created by the US Department of Transportation Bureau of Transportation Statistics to measure the movement of freight and passengers. The freight TSI consists of for-hire trucking; freight railroad services; inland waterway traffic; pipeline movements; and air freight.
The passenger TSI consists of local mass transit; intercity passenger rail; and passenger air transportation.
The sudden decline in the passenger TSI in September of 2001 is due to the events of September 11, 2001. The freight TSI experienced a decline in the late 2000’s during the time of the Great Recession.