An ongoing uptick in freight volumes and other data is leading to more guarded optimism on the outlook for the U.S. economy-- though caution is still the watchword cited by experts.

The American Trucking Assns’ (ATA) advanced seasonally adjusted for-hire truck tonnage index increased 2.1% in August, which follows a similar gain in July. Year over year, overall tonnage volume remains down – with August 2009 levels down 7.5% compared to August 2008. But Bob Costello, ATA chief economist, said that the latest monthly increase was another positive sign for the industry.

“The gains in tonnage during July and August reflect a growing economy and less of an overhang in inventories,” he explained. Though Costello remains hopeful that the overall trend in truck tonnage during the months ahead will be upward, he acknowledged that the pace of increase will likely moderate from the cumulative 4.3% gain over the last two months.

“While I am optimistic that the worst is behind us, most economic indicators, including industrial output and household spending, suggest freight tonnage will exhibit moderate, and probably inconsistent, growth in the months ahead,” he said.

Still, economic activity that generates freight demand is picking up. The Commerce Department’s Bureau of the Census noted that sales of new single-family houses edged up again for the third month in a row, increasing 0.7% in August. Though analysts had expected a 1.6% rise in August, Rebecca Blank, Commerce Under-Secretary for Economic Affairs, noted that new single-family home sales have risen 30.4% above their low in January of this year, with the inventory of new unsold homes dropping to 7.3 months of sales.

“The rise in new home sales so far this year has sparked an increase in building activity,” Blank added. “Residential construction is likely to grow this quarter after 14 consecutive quarterly declines. We are encouraged by the signs of stabilization in the housing market represented by today’s data on new home sales, helped by the strong fiscal and monetary actions that have been taken to stimulate economic growth.”

“Data in the past couple of months show continued improvement in real economic performance. In combination with the repair in financial markets, the outlook for gross domestic product (GDP) in the next few quarters appears better, improving the odds of a more enduring positive feedback loop arising from market developments and real activity,” stressed Kevin Warsh, Member of the Board of Governors of the U.S. Federal Reserve, in speech before the 12th annual International Banking Conference in Chicago last week.

However, that being said, the U.S. economy is not out of the woods yet, Warsh pointed out, with many risks that will bear close watching in the months ahead.

“The medium-term risks to the outlook are still disquieting,” he warned. “Policies, broadly defined, that purport to bring stability to the macro-economy could risk lowering output potential over the horizon. The uncertainty of the capital and labor reallocation process, a global trade environment in transition, and a shifting regulatory environment represent downside risks.”