The American Trucking Associations just released For-Hire Truck Tonnage Index increased 1.4% in September from the month before, matching the August gain.

In September, the seasonally adjusted index equaled 128.7 versus 126.9 in August. Compared with September 2012, the index surged 8.4%, which is the largest year-over-year gain since December 2011. Year-to-date, compared with the same period in 2012, the tonnage index is up 5.4%. 

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 128.1 in September, which was 2.5% below the previous month at 131.3. 

“I continue to be pleasantly surprised on the strength of truck tonnage,” said Bob Costello, ATA chief economist. “I attribute a part of tonnage’s robustness to the sectors of the economy that are growing fastest, like housing construction, auto production, and energy output. These industries produce heavier than average freight, which leads to faster growth in tonnage versus a load or shipment measure.

“While tonnage is likely running ahead of overall economic growth, perhaps the economy is stronger than many believe,” he said. The index has now increased in four of the last five months and the year-over-year growth rate has accelerated.

Costello noted other measures of truck freight volumes, while increasing at a slower pace than tonnage, have also accelerated in recent months, however, he says the government shutdown served as a headwind in the fourth quarter.