The American Trucking Associations' advance seasonally adjusted For-Hire Truck Tonnage Index increased 2.8% in June after decreasing a revised 2% in May 2011.

May's revised drop was slightly less than the 2.3% ATA originally reported on June 27. The latest gain put the SA index at 115.8 (2000=100) in June, up from the May level of 112.6 and the highest since January 2011.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 122.3 in June, which was 5.3% above the previous month.

Compared with June 2010, SA tonnage jumped 6.8%, the largest year-over-year gain since January 2011. In May, the tonnage index was 3% above a year earlier.

"Motor carriers told us that freight was strong in June and that played out in the data as well," ATA Chief Economist Bob Costello said. Tonnage recovered all of the losses in April and May when the index contracted a total of 2.6%.

"After growing 5.5% in the first half of the year from the same period last year, the strength of truck tonnage in the second half will depend greatly on what manufacturing output does," Costello noted. "If manufacturing continues to grow stronger than GDP, I fully expect truck freight to do the same."

Jefferies & Co., an investment banking group, pointed out that while truck tonnage captures most of the headlines, loads are an important indicator of volumes for truckload carriers. Volume leads price, they said in an investor e-mail, and sustained pricing gains will, to a large extent, hinge upon a reacceleration in truckload loads.

Jefferies' Peter Nesvold reports that growth in loads for large truckload carriers accelerated from +0.4% year-over-year in April to +3.9% year-over-year in May. Bulk chemicals was the only truckload trailer type in May to post a year-over-year gain in loads (+14.7%). Dry van volumes slipped 2% in May from the previous year, although that was the best YoY reading in nine months.