American Trucking Associations' advanced seasonally adjusted For-Hire Truck Tonnage Index fell 1.4% in January, following no change during December. In January, the index equaled 132.8 (2000=100), down from 134.7 in December, an all-time high (along with November 2015).

Compared with January 2015, the SA index was flat, which was down from December's 0.8% year-over-year gain. For all of 2015, compared with 2014, tonnage was up 2.6%.

ATA recently revised the seasonally adjusted index back five years as part of its annual revision. 

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 127.1 in January, which was 5.2% below the previous month (134.1).

"Clearly, 2016 started soft for truck tonnage," said ATA Chief Economist Bob Costello. "There was a deceleration in freight volumes during the second half of 2015 which continued into the first month of 2016.

"The winter storms that hit in January likely suppressed volumes some, but by falling 1.4%, I doubt tonnage would have been positive without the storms. So, that tells me that the inventory situation continues to weigh on truck freight volumes. The sooner the supply chain cleans out the excess stocks, the better for trucking," he said.

Trucking serves as a barometer of the U.S. economy, representing 68.8% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled just under 10 billion tons of freight in 2014. Motor carriers collected $700.4 billion, or 80.3% of total revenue earned by all transport modes.