The For-Hire Truck Tonnage Index hit an all-time high of 135.7 in January according to the seasonally adjusted report from American Trucking Associations. The index increased 1.2% in January and 6.6% compared with last January.

The 6.6% increase was the largest year-over-year gain in more than a year. Without seasonal adjustment, tonnage actually hauled by fleets equaled 126.9 in January which was down 3.5% from December.

ATA recently revised its seasonally adjusted index going back five years as part of the association’s annual revision. For all of 2014, truck tonnage was up 3.7%, slightly better than the 3.4% originally reported.

“Truck tonnage continued to improve in January, marking the fourth straight gain totaling 3.5%,” said Bob Costello, chief economist at ATA. “Last year was slightly better for truck tonnage than we originally thought and I am expecting that momentum to continue in 2015.”

ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. The report includes month-to-month and year-over-year results, relevant economic comparisons, and key financial indicators.