The American Trucking Associations' seasonally adjusted For-Hire Truck Index fell 2.3 percent sequentially in March to a reading of 113.2, the association said Tuesday.

Although the March index was down compared with February's revised reading, it rose 1.6 percent compared with March 2018, the Arlington, Va.-based association said. Quarterly results increased as well, with tonnage up 3.8 percent compared with the year-ago period.

Despite the year-over-year increases, ATA's leaders said they expect lower gains in for-hire truck tonnage this year compared with 2018.

"In March, and really the first quarter in total, tonnage was negatively impacted by bad winter storms throughout much of the U.S.," ATA Chief Economist Bob Costello said in a statement announcing the monthly results. "While I expected tonnage to moderate in the first quarter, the late Easter holiday and the winter storms made it worse. It is likely that tonnage will improve in the second quarter, although year-over-year gains will be significantly below the 2018 annual increase of 6.7%."

Trucking represents 70.2 percent of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods, ATA said. Trucks hauled 10.77 billion tons of freight in 2017, and motor carriers collected $700.1 billion, or 79.3 percent of total revenue earned by all transport modes, according to the association.