American Trucking Associations seasonally adjusted For-Hire Truck Tonnage Index has increased 0.7% in September after falling by 0.9% in the previous month.

The index equaled 135.1 which was up from the 134.1 it showed in August and neared its all-time high of 135.8 which was reached in January of this year. The Index is also up year-over-year with a increase of 3.1% compared to September 2014.

The not-seasonally adjusted index, that represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 138.9. It represents an increase of 1.4% above August.

“The see-saw pattern in truck freight tonnage continued again in September, except that the gain didn’t fully wipe out August’s decline” said Bob Costello, ATA chief economist. “However, over the last few months tonnage has snapped back from softness this past spring and early summer, and is approaching the record high.”

Despite the positive movement, Costello added that he is concerned about the high level of inventories in the supply chain. Inventories increased in August which could have a negative impact on freight volumes in the coming months, he said.