WASHINGTON — After some months of modest growth in 2008, the American Trucking Associations‘ For-Hire Truck Tonnage Index decreased 1.6 percent in August, the largest month-to-month drop since March.

Additionally, the index fell 0.9 percent in July, a downward revision from the 0.3-percent drop reported last month. In August, the seasonally adjusted tonnage index equaled 113.6 (2000 = 100), its lowest level since November 2007.

The seasonally adjusted index was 2.6 percent higher compared with August 2007, marking its 10th consecutive year-over-year increase. The gain was more than one percentage point lower than the improvement in July.

ATA Chief Economist Bob Costello said freight slowed during July and August preceding an expected slowdown in economic activity. "We are forecasting a mild recession later this year and early next year," he noted. "Make no mistake about it, freight volumes are weakening." Costello cautioned that year-over-year growth in the index is simply the result of soft tonnage volumes in 2007.

Because trucking is a leading economic indicator, Costello said trucking eventually will see an improvement before the overall economy, which has taken a severe beating in the U.S. in recent weeks.