ARLINGTON, Va. — Two consecutive months of increases in US truck tonnage came to a screeching halt in March, with the index plunging 4.5% and undoing all the early gains of 2009.

The American Trucking Associations (ATA), which tracks the data, reported a 4.5% month-over-month decline in tonnage in March, erasing a 4.5% gain in the first two months of 2009.

The seasonally-adjusted March figures were the lowest since March, 2002. The ATA reported fleets did see an increase in tonnage in March, but it was well below the 15-20% rise that’s usually experienced between February and March.

Tonnage was down 12.2% compared to March 2008, which was the second worst year-over-year decrease of the current cycle. The biggest drop was in December, 2008, which saw a 12.5% contraction compared to the year before.

ATA chief economist, Bob Costello, wasn’t overly surprised. He’s been warning fleets not to put too much stock in the small spikes experienced in January and February.

“Many fleets were telling us during March that freight was getting a little better. The problem is that freight should be significantly better in March, which is why the seasonally adjusted index fell,” Costello said. “While the industry is desperate for some positive news, it is unfortunate that March’s data suggests the industry has not hit bottom just yet.”