A monthly index of seasonally adjusted for-hire truck tonnage fell 4.5 percent in March, according to data released today by the American Trucking Associations (ATA), retracing more than 60 percent of February's surprising gain, which many thought was unsustainable.

The decline is the largest for the index since September 2012, when it contracted by 5.3 percent.

February's 7.2-percent increase from January's figures put the index at an all-time high. However, Donald Broughton, transport analyst for investment firm Avondale Partners LLC, said at an industry conference earlier this month that February's data was wildly overstated and that the increase was more along the lines of 2 percent.

Broughton said he forecasts traffic and pricing contraction for truckload carriers because retail sales activity remains moribund. Less-than-truckload (LTL) carriers have suffered since the fall of last year due to what is now widely believed to have been a months-long industrial recession.

Compared with March 2015, the seasonally adjusted index was up 2.2 percent, which was down from February's 8.6-percent year-over-year gain, ATA said. Year-to-date, compared with the same period in 2015, tonnage was up 3.9 percent, the trucking trade group said.

"The freight economy continues to be mixed, with housing and consumer spending generally giving support to tonnage, while new fracking activity and factory output (are) being drags," Bob Costello, ATA's chief economist, said in a statement. "In addition, freight volumes are softer than the overall economy because of the current inventory overhang throughout the supply chain."

In his comments, Broughton cast doubt on the notion that tonnage will pick up once the total business inventory-to-sales ratio, which measures the amount of inventory relative to final sales, comes down from multiyear highs. "It's not as if logistics managers suddenly forgot how to manage inventories," he told the Transportation Intermediaries Association's (TIA's) annual meeting last Saturday in San Antonio. "There's demand destruction going on out there."

February's inventory-to-sales ratio hit 1.41, according to data released last week by the Census Bureau. That is the highest level since mid-2009.

Data released today by Avondale and Cass Information Systems Inc., which audits and pays about $26 billion in freight bills, lends credence to the bearish stance. Cass' truckload line-haul index fell in March by 0.6 percent year-over-year, its first negative price change since May 2010. Its intermodal index dropped 3 percent year-over-year in March after declines of 2.2 percent and 3.8 percent, respectively, in January and February.

The truckload and intermodal data cover just the line haul and do not take into account fuel surcharges or other accessorial charges.