The American Trucking Assns.’ seasonally adjusted Truck Tonnage Index fell to 144.5 (1993=100) or 5.4% in May, the ATA has reported.

This is a preliminary figure and subject to change in its final report issued around the 5th day of every month. Compared to May 2002, the unadjusted index fell 1.3%.
In April, truck tonnage grew a solid 5.2% from March and 4.7% from April 2002. The index peaked at 157.2 in December 1999. For the last several months, truck tonnage has been in a seesaw pattern, but the underlying trend-line has been steadily increasing.
"The magnitude of May’s drop was a bit surprising, but the fact that tonnage decreased during the month was not," said Bob Costello, ATA chief economist and vice president. "Truck tonnage has been exhibiting significant swings lately, which is indicative of a slow-growing economy," Costello said.
The bigger surprise was that the index decreased from a year earlier after solid year-over-year growth the last eight months. "Certainly one month doesn’t make a trend, and this could be an anomaly considering how volatile the data have been recently," he said. "Nevertheless, the foundation appears to be in place for more solid truck tonnage growth later in the year, including tighter trucking capacity, accommodative monetary and fiscal policy, and lean business inventories."
ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. The association releases a full report on the index during the first full week of every month.
Trucks hauled 8.9 billion tons of freight in 2002, or 67.9% of all tonnage carried by all modes of domestic freight transportation. Motor carriers collected $585 billion dollars or 86.5% of all revenues earned by all modes.