The American Trucking Associations’ advanced seasonally adjusted truck tonnage index fell 1% in March, giving a reading of 137.5.

Rough weather in the month was to blame for the depressed truck tonnage numbers, according to ATA. Despite the drop, March’s numbers were slightly better in year-over-year comparisons.

“Like several other economic indicators, March truck tonnage was likely hurt by some late season winter storms,” said Bob Costello, ATA chief economist. “Despite last month’s dip,  seasonally adjusted tonnage rose 1.2% during the first quarter overall from the previous quarter, and increased 0.2% from the same quarter last year.”

Without seasonal adjustment, March was 14.6% better than February but this was mostly attributed to the shorter month and other similar factors, which is why ATA adjusts the index to make better comparisons. Going forward, truck tonnage is expected to see some growth.

“While I’m not expecting a surge in truck tonnage anytime soon, the signs remain mostly positive for freight, including lower inventory levels, better manufacturing activity, solid housing starts and good consumer spending,” said Costello. “As a result, we can expect moderate growth going forward.”