A summertime slide in retail sales caused the nation's truck tonnage to fall in August. That was the second consecutive monthly decline reported by the American Trucking Associations (ATA).

The Alexandria, Va.-based organization said that its truck tonnage index for August fell 1.3 percent, to 157.9. The index, which is based on the results of surveys of ATA members in various industry segments, serves as a barometer of truck freight volumes and general economic activity.

"Truck tonnage data for July and August, on a month-to-month basis, show an economy that took a breather, especially in retail sales," said Robert Costello, the trucking group's chief economist.

Despite that decline, the year-to-date index for 2004 remains 7.2 percent higher than it was for the same period in last year.