ARLINGTON, Va. — US for-hire truck tonnage fell 4.3% in January, but you can blame the weather.

The American Trucking Associations said its tonnage index was still up 1.2% year-over-year. The softening from December was attributed to winter storms, and not a weakening of the economy or of freight demand. The index finished 2013 up 6.3% compared to 2012.

“Like most economic indicators, truck tonnage was negatively impacted by bad winter weather in January,” said ATA chief economist Bob Costello. “The thing about truck freight is that it’s difficult to catch up. Drivers are governed by hours-of-service regulations and trucks are limited to trailer lengths and total weights, thus it is nearly impossible to recoup the days lost due to bad storms.” 

As such, Costello said it’s tough to gauge January’s demand.

“January wasn’t just one storm, it was several across a large part of the country. Therefore, I wouldn’t panic from the largest monthly drop in two years,” Costello said. “I’ve heard from many fleets that freight was good, in-between storms. The fundamentals for truck freight still look good.”