A new report shows the amount of freight moved in the final month of last year was unchanged from the month before but posted a healthy gain for all of last year.

The American Trucking Associations' advanced seasonally adjusted For-Hire Truck Tonnage Index remained at 136.8 in December, following a jump of 3.5% during the previous month, which tied the all-time high.

Compared with December 2013, the index increased 5.2%, which was the largest year-over-year gain in 2014. For all of 2014, tonnage was up 3.5% over 2013.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, registered 133.5 in December, 6.1% above the previous month at 125.8.

"Economic data was mixed in December, with retail sales down 0.9% and factory output up 0.3%, so tonnage was in-between those two readings, which are two large drivers of truck freight," said ATA Chief Economist Bob Costello. "Overall, 2014 was a good year for truck tonnage with significant gains throughout the year after falling 4.5% in January alone."

Costello said that in December 2014, tonnage was 10.2% above the January 2014 level.

"Freight volumes look good going into 2015," he said. "Expect an acceleration in consumer spending and factory output to offset the weakness in hydraulic fracking this year."

Trucking serves as a barometer of the U.S. economy, representing 69.1% of tonnage carried by all modes of domestic freight transportation. ATA calculates the tonnage index based on surveys from its membership