CALVERTON, MD. — Total intermodal shipments in Canada and the U.S. rose 2% from the same time a year earlier, according to new a Intermodal Association of North America report, despite port congestion issues that impacted international container traffic.

Domestic intermodal loads in the two countries combined grew 4.5%, buoyed by domestic containers, which rose 6.5% in a quarter-over-quarter comparison.

“Monthly first quarter results were uneven due to the issues on the U.S. West Coast,” said Joni Casey, president and CEO of IANA. “Despite February’s challenges, however, we still saw some overall quarterly growth, led by big boxes in regions less affected by port congestion.”

Regional traffic growth remained tied to port issues, despite the relative strength of domestic intermodal in Canada and the U.S. Also, a significant share of U.S. West Coast freight was diverted to other ports, particularly in Canada, and moved by rail.

Western Canada posted the strongest growth rate of any region in the two countries, jumping 10.6% in the first quarter. Eastern Canadian volumes gained a weaker, but still impressive 5.9%.

“Both regions benefitted from strong international shipment growth. Western Canada’s international volumes jumped 12% in the first quarter, while Eastern Canada’s international volumes rose by 9%,” said the report.

Domestic container growth in these two regions was weaker than the overall industry average at just about 5%, but that is not surprising, according to IANA, because there is a much longer distance between Canada’s major markets than in the U.S., and rail has a larger market share than in the U.S.

“This means that intermodal gains in Canada are much more dependent on overall economic growth. They simply don’t benefit as much from share gains from trucking,” the group said.

Total Eastern Canada growth was dragged down by particularly poor trailer performance. Total trailer shipments in Eastern Canada fell by 13.6% in the first quarter. In contrast, trailer volumes are on an upswing in Western Canada, but to little effect because trailers comprise just 0.1% of all intermodal originations in Western Canada, according to IANA.

The Trans-Canada lane also did better than the industry average. Both domestic and international containers saw growth of around 5%. Shipments from Eastern Canada to Western Canada did slightly better than the reverse, a 5.7% improvement versus a 4.4% gain.

South of the border, volumes were down in the U.S. Southwest, which saw a 5.7% decline over the first quarter 2014. The U.S. Southeast surged 9.9% due to increases in both domestic and international containers.

The seven largest volume corridors also varied according to their exposure to port disruptions.

While lanes that included the U.S. Southwest were down, the intra-U.S. Southeast continued to be an intermodal powerhouse. Intermodal shipments in that lane jumped 16.5% in a quarter-over-quarter comparison. Overall, high-density lanes, which accounted for 64.5% of total volumes, saw a minimal decline of 0.9% in the first quarter.

Intermodal marketing companies reported 3% growth in the first quarter, laying the groundwork for an even stronger performance in the coming months. They saw itermodal and highway loads jumping 3.2% and 2.6%, respectively.