The American Trucking Assns. (ATA) said its advanced seasonally adjusted Truck Tonnage Index dropped by 2.3% to 152.2 (1993=100) in January. The decrease followed a revised increase of 2.6% in December to an all-time high level.

From December to January, the unadjusted index fell 3.1%. Compared to January 2003, the unadjusted index rose 0.4%.
In arriving at the January number, seasonally adjusted data were revised back to 1973 using different estimation techniques. The resulting series says ATA chief economist Bob Costello, is "much less volatile" than previously published.
"The newly revised seasonally adjusted data are a much better indication of truck freight volumes than we have been reporting", said Costello. "As a result, January was the first month since August 2003 that tonnage fell on a seasonally adjusted basis." Costello said he believed that the bad winter weather during the last week of January magnified the decrease in truck tonnage for the month.
Trucks hauled 8.9 billion tons of freight in 2002, or 67.9% of tonnage carried by all modes of domestic freight transportation. Motor carriers collected $585 billion dollars, or 87% of total revenue earned by all transport modes.
ATA calculates the tonnage index based on surveys from its membership, and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report issued around the seventh day of every month. The report includes month-to-month and year-over-year results, relevant economic comparisons and key financial indicators.
The ATA is the largest national trade association for the trucking industry. Through a federation of other trucking groups, industry-related conferences, and its 50 affiliated state trucking associations, ATA represents more than 37,000 members covering every type of motor carrier in the United States.