ARLINGTON, VA – Truck tonnage in the U.S. rose 5.7% in August, following a 2.1% drop in July, according to the American Trucking Associations’ advanced seasonally adjusted For-Hire Truck Tonnage Index.

Year to date, when compared to the same period in 2015, tonnage was up 3.5%.

“Volatility continues to reign in 2016. This month’s tonnage reading highlights this fact and underscores the difficulty in determining any real or clear trend in truck tonnage,” said Bob Costello, the association’s chief economist. “What is clear to me is that normal seasonal patterns are not holding in 2016.”

Compared to last August, the index rose 5.9%, representing the largest year-over-year gain since May. In contrast, July’s numbers represented a year-over-year increase of just 0.2%.

When not accounting for seasonal adjustments, the tonnage actually hauled by fleets was 4.8% above the previous month. In the previous three years, the average August changes were just 0.3%.

“Despite a difficult to read August, I expect the truck freight environment to be softer than normal as well as continued choppiness until the inventory correction is complete. With moderate economic growth forecasted, truck freight will improve as progress is made with the inventory overhang,” Costello said.

Trucks move 68.8% of the freight tonnage in the U.S., and hauled just under 10 billion tons of freight in 2014.