The American Trucking Associations’ advanced seasonally adjusted For-Hire Truck Tonnage Index gained 0.9% in March after decreasing 0.7% in February.

Tonnage has now increased in four of the last five months. Specifically, since November 2012, the index is up 7.6%. In March, the SA index equaled 123.5 (2000=100) versus 122.3 in February.

The highest level on record was December 2011 at 124.3. Compared with March 2012, the SA index was up a solid 3.8%, beating February’s 3.1% year-over-year gain. Year-to-date, compared with the same period in 2012, the tonnage index is up 3.9%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 125.2 in March, which was 11.5% above the previous month.

“Fitting with the expectation for solid gross domestic product growth in the first quarter, tonnage was strong in March and the quarter overall,” ATA Chief Economist Bob Costello said. “At 3.9% year-over-year growth, the first quarter increase was the best since the final quarter 2011.

“Expect freight tonnage will slow in the months ahead as the federal government sequester continues and households finish spending their tax returns,” he said. “The good news for tonnage is housing starts are growing and energy production is good – both of which generates heavy freight. However, these two sectors alone won’t be enough to keep the overall index growing at a 3.9% clip in the second quarter.”