The Cass Freight Index, which measures shipment activity in trucking and other transport modes, declined 0.4% in August from a year ago.
The report from Cass Information Systems, St. Louis, also noted a 1.7% increase in shipping activity in August from July.
The month-to-month rise matched predictions that 2013 will have a peak holiday shipping season, the index said.
According to the report, there is a looming capacity problem in the trucking sector with more than 95% capacity utilization and an abundance of regulatory and cost pressure.
“The tricky part is forecasting when demand will actually exceed capacity. The economy is growing slowly enough that the tipping point remains just on the horizon,” according to the report.