The American Trucking Associations’ advanced seasonally adjusted For-Hire-Truck Tonnage Index slid 2.5% in April, marking the third straight month of declines.

The index for April equaled 134, down from 137.4 in March. Compared to last April, the index was down 1.8%, a change in trends from March, which showed a slight year-over-year increase. More telling was the not-seasonally adjusted index, which showed a drop of 7.8% from March.

“I have to admit that April’s contraction is a bit surprising, especially considering the anecdotal reports I’ve been hearing from fleets regarding freight levels,” said Bob Costello,  ATA chief economist. “It’s not necessarily that tonnage levels fell in April that is surprising, but the size of the decrease.”

Some economic indicators were pointing toward improved freight and ATA was expecting to see a corresponding boost in the index, however, a 2.6% drop in housing starts may have contributed to the decline, as residential construction generates heavier truck freight. The weight is important because the Truck Tonnage Index measures the weight of loads, not the amount.

“Despite the fact that tonnage is down a total of 3.6% over the last three months, I still expect moderate growth going forward as key sectors of the economy continue to improve slowly,” said Costello.

Additional data from industry intelligence firm FTR adds a little more perspective. "Our loadings data shows a 1% increase from March to April, after a 1.3% drop the prior month," said Jonathan Starks, chief operating officer for FTR. "Our tonnage data shows a 0.7% increase in April following a 2% decline in March. Short-haul, heavy freight (i.e. stone, asphalt, etc.) had a big surge in February and has come back down to earth the last two months." Compared to the previous year, FTR's numbers show loadings up 4.4% in April and tonnage up 3.7%.

Updated 5:10 p.m. EDT 5/23 to add FTR data