Compared with September 2015, the SA index fell 0.7%, the first year-over-year decline since October 2015. In August, the year-over-year increase was 5.2%. Year-to-date, compared with the same period in 2015, tonnage was up 3%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 136.4 in September, which was 5.1% below the previous month (143.8).

“Volatility this year continued again in September with the large drop after a significant increase in August,” said ATA Chief Economist Bob Costello. “The changes we’re seeing in typical seasonal trends are making it difficult to discern any real or clear trend in truck tonnage.

“Adjusting for the larger ups and downs this year, as well as talking with many fleets, I currently see a softer than normal freight environment, which is likely to continue until the inventory correction is complete. Looking ahead, the slow growth economic environment does not suggest that significantly stronger truck tonnage numbers are in the near term either,” he said.