The Bureau of Transportation Statistics (BTS) recently released a new technical report, Transportation Services Index and the Economy—Revisited, that confirms that the Transportation Services Indexes (TSIs) both lead the economy, though in different ways.

BTS extended the TSI back to 1979, examining five re­cessions and numerous growth cycles. “When the accelerations and decelera­tions of the freight TSI are compared to the growth cycles of the economy, the freight measure leads by an average of approximately four months,” BTS said. “The passenger TSI exhibits fewer turning points, which were then identified as leading the business cycles of re­cession and expansion, also by approximately four months.”

The September 2014 Freight TSI rose for the third consecutive month and is now 2.1 percent higher than at the beginning of 2014.

The Freight TSI measures the month-to-month changes in freight shipments by mode of transportation in tons and ton-miles, which are combined into one index. The index measures the output of the for-hire freight transportation industry and consists of data from for-hire trucking, rail, inland waterways, pipelines and air freight. The passenger TSI measures the month-to-month changes in travel that involves the services of the for-hire passenger transportation sector. The seasonally-adjusted index consists of data from air, local transit and intercity rail.