The American Trucking Associations’ advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index increased 1.2% in June 2012 after falling 1.0% in May. May’s loss was larger than the 0.7% drop ATA reported June 19.

June’s increase was the largest month-to-month gain in 2012. However, the index contracted a total of 2.1% in April and May. The latest gain increased the SA index to 119.0 (2000=100), up from May’s level of 117.5. Compared with June 2011, the SA index was 3.2% higher—the smallest year-over-year increase since March 2012. Year-to-date, versus the same period in 2011, 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, equaled 123.0 in June 2012, which was 0.9% below the previous month.

For the 2012 second quarter, the SA 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 Bob Costello, ATA chief economist. “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 these actions would give the economy and tonnage a shot in the arm, as Europe and the US could face a fiscal cliff at the end of the year. He lowered his tonnage outlook for 2012 to the 3% to 3.5% range due to recent economic weakness.

Trucking serves as a barometer of the US economy, representing 67% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 9.2 billion tons of freight in 2011. Motor carriers collected $603.9 billion, or 80.9% of total revenue earned by all transport modes.