Despite network congestion and economic headwinds, intermodal freight saw solid growth in 2015, but the level of freight was barely up in the final quarter, according to the Intermodal Association of North America.

Domestic container gains more than offset declines in trailer volumes and marginal international increases to achieve 2.8% growth in total intermodal volumes last year over 2014.

"All things considered, intermodal performed well for the year," said Joni Casey, president and CEO of IANA. "Even as fuel prices were dropping, domestic container volumes were picking up. This smoothed variations across segments, especially in the fourth quarter."

The domestic container segment grew 5.2% in the fourth quarter of 2015. International shipments, which had been affected by port congestion at the beginning of the year, fell 0.6% due to high inventories and softer import growth. Fourth quarter trailer volumes dropped 15% while the overall intermodal sector saw just a 0.3% gain for the quarter.

The seven highest-density trade corridors, accounting for 66% of total intermodal volume, fell 0.2% in the fourth quarter against the small industry gain. Growth rates for each individual corridor varied widely.

The intra-Southeast corridor led with 9.7%, reflecting the strength of both international and domestic containers in that lane, while South Central-Southwest corridor volumes decreased by an equal amount.

Intermodal service providers demonstrated clear growth in the highway sector during fourth quarter, up by 11.4%, while intermodal loads remained flat. The net result was a volume increase of 4.8%. On an annual basis, highway loads increased 9.5% compared to 2.3% for the intermodal sector, with overall growth of 5.3%.