The Bureau of Transportation Statistics’ Transportation Services Index (TSI) measures the volume of freight and passenger transportation services moved monthly by the for-hire transportation sector in the United States. BTS produces three indexes: a freight index, a passenger index, and a combined index. The indexes incorporate monthly data from multiple for-hire transportation modes. 

Changes in the TSI reflect changes in the demand for goods and services. For example, in periods of economic expansion the demand for goods and services typically increases, which in turn increases the demand for transportation reflected by an increase in the TSI.