The American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index decreased 3.8% in October after falling 0.4% in September. (The 0.4% decrease in September was revised from a 0.1% gain ATA reported on October 23, 2012.) October's drop was the third consecutive totaling 4.7%. As a result, the SA index equaled 113.7 (2000=100) in October, the lowest level since May 2011. Compared with October 2011, the SA index was off 2.1%, the first year-over-year decrease since November 2009. Year-to-date, compared with the same period last year, tonnage was up 2.9%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 123.7 in October, which was 7.7% above the previous month.

'Clearly Hurricane Sandy negatively impacted October's tonnage reading,' ATA Chief Economist Bob Costello said. 'However, it is impossible for us to determine the exact impact.'

Costello noted that a large drop in fuel shipments into the affected area likely put downward pressure on October's tonnage level since fuel is heavy freight, in addition to reductions in other freight.

'I'd expect some positive impact on truck tonnage as the rebuilding starts in the areas impacted by Sandy, although that boost may only be modest in November and December,' he said. 'Excluding the Hurricane impacts, I still think truck tonnage is decelerating along with factory output and consumer spending on tangible-goods.'

Note on the impact of trucking company failures on the index:Each month, ATA asks its membership the amount of tonnage each carrier hauled, including all types of freight. The indexes are calculated based on those responses. The sample includes an array of trucking companies, ranging from small fleets to multi-billion dollar carriers. When a company in the sample fails, we include its final month of operation and zero it out for the following month, with the assumption that the remaining carriers pick up that freight. As a result, it is close to a net wash and does not end up in a false increase. Nevertheless, some carriers are picking up freight from failures and it may have boosted the index. Due to our correction mentioned above however, it should be limited.

Trucking serves as a barometer of the U.S. economy, representing 67% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 9.2 billion tons of freight in 2011. Motor carriers collected $603.9 billion, or 80.9% 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 10th day of the month. The report includes month-to-month and year-over-year results, relevant economic comparisons, and key financial indicators.