The American Trucking Associations' For-Hire Truck Tonnage Index jumped 2.8% in July, following a revised drop of 0.4% during June.

In July, the seasonally adjusted index equaled 135.0 (2000=100), the second highest level on record. The all-time high of 135.8 was reached in January 2015.

Compared with July 2014, the SA index increased 3.7%, which was above the 1.9% gain in June. Year-to-date through July, compared with the same period last year, tonnage was up 3.4%.

“After several soft months starting in February, tonnage really snapped back in July,” said ATA Chief Economist Bob Costello. “July was the single best monthly gain since November 2013.”

Costello said a few factors added to July’s strength, including better retail sales, factory output, and housing starts. “However, I remain concerned in the near term about the high level of inventories throughout the supply chain. This could have a negative impact on truck freight volumes over the next few months.”

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 137.3 in July, which was 0.8% below the previous month (138.4).

ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report issued around the 10th day of the month.