ARLINGTON, Va. -- The American Trucking Associations' tonnage index fell 0.7 percent in April after gaining a revised 1.9 percent in March 2011, as durable goods orders slowed.

Compared with April 2010, seasonally tonnage climbed 4.8 percent. In March, the tonnage index was 6.5 percent above a year earlier.

However, freight levels are predicted to continue moderate growth, according to the ATA.

"The drop in April is not a concern. Since freight volumes are so volatile truck tonnage is unlikely to grow every month, even on a seasonally adjusted basis," ATA Chief Economist Bob Costello said. "I expect economic activity, and with it truck freight levels to grow at a moderate pace in the coming months and quarters."

"The industry, and the economy at large, should benefit from the recent declines in oil and diesel prices," Costello added. "Lower fuel costs will help freight volumes and motor carrier bottom lines going forward."

Meanwhile, Peter Nesvold of Jeffries & Co. says that while tonnage captures most of the headlines, loads are actually a more important indicator of volumes for truckload.

In March, bulk chemicals was the only truckload trailer type in to post a year-over-year gain (+15.5%). Dry van volumes continued to fall, contracting 7.3 percent. "Our work has found that truckloads typically peak out earlier than tonnage as the cycle matures," he wrote in a memo to investors.

Yet pricing, including in dry van, holds firm.

"Notwithstanding decelerating load growth, we remain impressed with the strength in truckload pricing."

Dry van pricing continues to track at the "high-end of expectations." (+9.6%).

Revenue per mile, net of fuel, was up 6.2 percent YoY in March. Short-haul (less than 500 miles) pricing is weak, though, down 3.9 percent.

"We continue to believe that volume leads price and that sustained pricing gains will, to a large extent, hinge upon a reacceleration in truckloads -- and not just supply-side capacity rationalization."