Truck tonnage may have increased 2.9% year-over-year in August, but the collapse in month-over-month levels is much more illuminating.

Tonnage fell by 2.7% from July to August, according to the American Trucking Association.

That's the biggest month over month fall since March 2009.

The chief economist at the ATA, Bob Costelo, says this slowdown was expected and that it should be slowing further with the economy for the remainder of the year.

From the American Trucking Association: