ARLINGTON, Va. — US for-hire truck tonnage increased 1.2% in June after falling 1.0% in May, according to a report from the American Trucking Associations. (May’s loss was larger than the 0.7% drop ATA reported on June 19.) June’s increase was the largest month-to-month gain in 2012. However, the seasonally-adjusted index contracted a total of 2.1% in April and May. Compared with June 2011, the index was 3.2% higher, the smallest year-over-year increase since March. Year-to-date, compared with the same period last year, tonnage was up 3.7%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, was 0.9% below the previous month.

For the second quarter, the seasonally-adjusted index was off 0.8% from the previous quarter, which was the first decrease in a year. Compared with the second quarter in 2011, the index was up 3.5%.

“June’s increase was a pleasant surprise, but the lower year-over-year gain fits with an economy that has slowed,” said ATA chief economist Bob Costello. “Manufacturing output was strong in June, which helped tonnage levels.”

Costello said he’s still concerned about businesses sitting on cash instead of hiring more workers or spending it on capital, both of which would give the economy and tonnage a shot in the arm, as they are worried about Europe and the so-called US “fiscal cliff” at the end of the year. Costello lowered his tonnage outlook for 2012 to the 3-3.5% range due to recent economic weakness.