ARLINGTON, Va., March 19, 2013 /PRNewswire-USNewswire/ -- The American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index rose 0.6% in February after increasing 1% in January. (The 1% gain in January was revised down from a 2.4% increase ATA reported on February 19, 2013.) Tonnage has now increased for four straight months, which hasn't happened since late 2011. Over the last four months, tonnage gained a total of 7.7%. In February, the SA index equaled 123.6 (2000=100) versus 123.0 in January. The highest level on record was December 2011 at 124.3. Compared with February 2012, the SA index was up a solid 4.2%, just below January's 4.6% year-over-year gain. Year-to-date, compared with the same period in 2012, the tonnage index is up 4.4%. In 2012, tonnage increased 2.3% from 2011. (Logo: http://photos.prnewswire.com/prnh/20100129/ATALOGO) The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 113.5 in February, which was 5.5% below the previous month (120.1). "Fitting with several other key economic indicators, truck tonnage is up earlier than we anticipated this year," ATA Chief Economist Bob Costello said. "While I think this is a good sign for the industry and the economy, I'm still concerned that freight tonnage will slow in the months ahead as the federal government sequester continues and households finish spending their tax returns. A little longer term, I think the economy and the industry are poised for a more robust recovery." 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. Trucking serves as a barometer of the U.S. economy, representing 67% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 9.2 billion tons of freight in 2011. Motor carriers collected $603.9 billion, or 80.9% of total revenue earned by all transport modes. ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report issued around the 10th day of the month. The report includes month-to-month and year-over-year results, relevant economic comparisons, and key financial indicators.