ARLINGTON, Va. — The American Trucking Associations‘ advance seasonally adjusted For-Hire Truck Tonnage Index dropped 2.3 percent in May after decreasing a revised 0.6 percent in April.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, was actually 2 percent above the previous month.

Compared with May 2010, though, tonnage climbed 2.7 percent, although this was the smallest monthly year-over-year gain since February of last year.

"Truck tonnage over the last four months shows that the economy definitely hit a soft patch this spring," ATA Chief Economist Bob Costello said. "With our index falling in three of the last four months totaling 3.7 percent, it is clear why there is some renewed anxiety over the economic recovery."

However, Costello added that he is cautiously optimistic that freight volumes will improve in the second half of the year along with economic activity.

"With oil prices falling and some of the Japan-related auto supply problems ending, I believe this was a soft patch and not a slide back into recession, and we should see better, but not great, economic activity in the months ahead," he said.