The not seasonally adjusted index increased 3.8 percent from February to 113.2.
The seasonally adjusted tonnage index equaled 113.4 (2000 = 100) in March, its lowest level since November 2007. Additionally, tonnage contracted 0.2 percent compared with March 2007, marking the first year-over-year decrease in the index since October 2007.
ATA Chief Economist Bob Costello said the latest tonnage reading was a significant setback. "I've been concerned that the recent run-up in tonnage might not be sustainable, and clearly March's figures confirmed that apprehension," he said.
Costello continues to forecast a mild recession for the overall economy during the first half of 2008, but noted that March's tonnage drop might suggest the economic contraction could be more severe than previously thought.
"Truck tonnage often leads both recoveries and recessions, and the latest contraction suggests the economy and trucking are not out of the woods yet," Costello said. "Surging diesel and gasoline prices are weighing heavily on consumers, and since trucks haul virtually all consumer goods at some point in the supply chain, the industry is going to be significantly impacted both directly through higher diesel prices and indirectly through lower freight volumes."