Newly released figures show U.S.-NAFTA freight totaled $100.6 billion in August, increasing 4.4% from the same time a year ago and marking the sixth consecutive month it exceeded $100 billion.

U.S. freight movements with Canada and Mexico saw imports increase 3.6% while exports gained 5.2% from a year earlier, according to the U.S. Transportation Department.

In August, the value of commodities moving by vessel grew by the largest percentage of any mode, 11.7%. Pipeline freight increased 6.8% followed by a rail increase of 3.4%, a truck increase of 3.3% and an air increase of 2.3%.

Of the $4.2 billion increase in the value of US-NAFTA freight from August 2013, truck freight contributed the most at $1.9 billion, followed by rail at $514 million. The trucking increase was due almost entirely to growth in truck freight with Mexico as U.S.-Canada truck trade remained almost unchanged, according to the department.

In August 2014, the top commodity category transported between the U.S. and Canada was mineral fuels, of which 56% moved by pipeline. The top commodity category transported between the U.S. and Mexico during the same time was electrical machinery, of which 91.7%, moved by trucks.

Trucks carry three-fifths of U.S.-NAFTA freight and are the most heavily utilized mode for moving goods to and from both U.S.-NAFTA partners, transporting 59.6% of U.S.- Canada and Mexico freight in August.

U.S.-Canada Freight

Year-over-year, the percent change in the value of U.S.-Canada freight moved by vessel increased the most of any mode, growing 46.9% driven primarily by exports of mineral fuels. Freight moved by pipeline increased 6.1% and rail increased by 2.2%, while truck and air were essentially unchanged.

Trucks carried 53% of the freight to and from Canada, followed by rail at 16.4%, pipeline at 12.8%, vessel at 7.1% and air at 4.3%. The surface transportation modes of truck, rail and pipeline carried 82.2% of the total U.S.-Canada freight flows.

U.S.-Mexico Freight

Year-over-year, the value of pipeline freight rose 21.1%, the largest percentage increase of any U.S.-Mexico mode. Freight moved by air increased 6.7%, truck by 6.6% and rail by 5.2%. Vessel decreased by 5.3%, principally due to a decline in mineral fuels imports, according to the department.

Trucks carried 67.7% of the freight to and from Mexico, followed by rail at 14.4%, vessel at 11.7%, air at 2.9% and pipeline at 0.8%. The surface transportation modes of truck, rail and pipeline carried 82.9% of the total U.S.-Mexico freight flows.