The American Trucking Associations' advance seasonally adjusted For-Hire Truck Tonnage Index increased 3.8 percent in January after rising a revised 2.5 percent in December 2010.

The latest jump put the SA index at 117.1 (2000=100) in January, which was the highest level since January 2008. In December, the SA index equaled 112.7.

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 105.4 in January, down 2.9 percent from the previous month.

Compared with January 2010, SA tonnage climbed 8 percent, which was the largest year-over-year increase since April 2010. For all of 2010, tonnage was up 5.7 percent compared with 2009.

ATA Chief Economist Bob Costello said that he was very pleased with January's robust gain, especially considering the winter storms during the month. "Many fleets told us that freight was solid in January, although operations were as challenge due to the winter storms that hit large parts of the country," he said, noting that the latest tonnage numbers indicate that the economy is growing at a good clip early in 2011 and he expects a solid first half of the year. "At this point, the biggest threat is the recent run-up in oil prices, which could dampen consumer spending."

Note on the impact of trucking company failures on the index: Each month, ATA asks its membership the amount of tonnage each carrier hauled, including all types of freight. The indexes are calculated based on those responses. The sample includes an array of trucking companies, ranging from small fleets to multi-billion dollar carriers. When a company in the sample fails, we include its final month of operation and zero it out for the following month, with the assumption that the remaining carriers pick up that freight.

As a result, it is close to a net wash and does not end up in a false increase. Nevertheless, some carriers are picking up freight from failures and it may have boosted the index. Due to our correction mentioned above however, it should be limited.