The value of freight shipments between the United States and its partners in the North American Free Trade Agreements—Canada and Mexico—fell by 6.8 percent April as compared to the same month last year.

Total U.S.-NAFTA freight in April amoutned to $93.3 billion, according to numbers released last week by the Bureau of Transportation Statistics (BTS), a branch of the U.S. Department of Transportation. The decrease in April followed a 5.3 percent decline to $96.1 billion in March.

The decrease in april was due mainly to falling fuel prices, decreasing the value of those shipments.

The shortfall was felt across all modes if transportation except air. The value of air shipments increased by three percent. At the same time, rail freight and truck freight each declined by 0.9 percent, and waterborne freight fell by 22.8 percent. Pipeline freight values, where the lower prices of fuel shipments hit hardest experienced the most dramatic decline, at 44.9 percent.

Trucks were the most frequently used mode of transportation for NAFTA freight, at 64.2 percent. Trucks transported 60.8 percent, or $29.8 billion, of the $49.1 billion of U.S.-NAFTA’s imports and 67.9 percent, or $30.1 billion, of $44.3 billion in exports.