Bulk railcar shipments at major U.S. railroads were down another 15 percent in the latest week, but "it appears as though things may be bottoming," said Tom White, spokesman for the Association of American Railroads.

White has prepared the railcar reports for many years, and said normally the year-over-year changes provide the best indicator of economic demand. But he said after such a sharp drop as in recent months the sequential performance provides some guidance.

Large U.S. railroads originated 279,287 railcar loads in the week ending March 14, of everything from bulk commodities to large equipment such as automobiles or construction gear but not including intermodal containers and trailers.

That was a 1.5 percent gain from the March 7 week, said White, and the latest in a series of weeks when carloads have fluctuated in a narrow range of 275,000 to as much as 285,000 shipments. "That sort of indicates that things, perhaps, are bottoming out," instead of continuing downward, he said.

In mid-January, by contrast, White said carload volume was below the 250,000 level.

"It seems to me that when you're in this sort of economy, you take a little bit of look at whether there's beginning to be a week-to-week uptrend," he said.

AAR said intermodal traffic fell 18.3 percent in the March 14 week, worse than the year-to-date's 15.8 percent drop. But the latest weekly carload decline was not as bad as some other weeks, as carloads are down 15.7 percent over the first 10 weeks of 2009.

AAR said carloads in the second week of this month were down 14.2 percent in the West and 16.1 percent in the East from a year earlier.

And while traffic in nearly all carload categories was down from the same point in 2009, 10 showed higher actual volume than a week ago.