From the Transportation Fact of the Week out of the US Department of Energy

In August of 2018, the freight Transportation Services Index (TSI) grew to 135.3 which is 105% higher than when the index began in January 1990. The TSI was created by the U.S. 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.