The American Trucking Associations’ advanced seasonally adjusted For-Hire Truck Tonnage Index increased 0.6% in March, after jumping 1.9% the previous month, according to just released figures.

February’s gain was less than the 2.8% originally reported by the group.

In March, the index equaled 127.3 versus 126.5 in February. The all-time high was in November 2013 at 131.

Compared with March 2013, the index increased 3.1%, which is the largest year-over-year gain of 2014. During the first quarter, tonnage plunged 2.5% from the previous quarter, which was the worst quarter-to-quarter reading since the economic recovery began in the third quarter of 2009. Compared with the first quarter 2013, tonnage rose 2.3%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 129.4 in March, which was 12.1% above the previous month at 115.5.

“Tonnage continued to claw its way out of the hole that was dug in December and January,” said ATA chief economist Bob Costello. “However, with a cumulative gain of 2.5% during the last two months, we still have a way to go to offset the total loss of 5.2% in December and January.

“Despite the fact that tonnage hasn’t snapped back to the levels we saw late last year, the fundamentals for truck freight continue to look good,” he said. “While it will take time to regain what was lost due to weather and other factors, like a potential inventory correction in the first quarter, I remain optimistic for 2014, however, don’t expect a 6.3% annual gain in truck tonnage like during 2013.”

ATA calculates the tonnage index based on surveys from its membership.

Trucking serves as a barometer of the U.S. economy, representing 68.5% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods.