Intermodal traffic increased in the first quarter by 7.2 percent over the same period in 2017, posting its largest rise in nearly four years, the Intermodal Association of North America (IANA) said today.

Volumes for the quarter met their strongest gain since the second quarter of 2014, pushed in part by shippers converting their traffic from highway carriers because they are finding it hard to get truck capacity, according to the Calverton, Md.-based intermodal trade group's quarterly report on the state of the industry, the **ital{Intermodal Market Trends & Statistics}report.

"Drivers for first-quarter growth were an overall strong economy, the continued growth of imports, higher fuel prices, tight over-the-road capacity, and weak comparisons to lower 2017 volumes in some markets," IANA President and CEO Joni Casey said in a statement.

Trailers led overall growth at 14.5 percent, international intermodal volumes rose 7.0 percent, and domestic containers increased 6.2 percent, the report said.

Broken out by geography, the seven highest-density trade corridors accounted for 62.8 percent of total volumes and were collectively up 6.2 percent, IANA said. The Northeast-Midwest performed the best of the seven, with volumes gaining 12.3 percent, followed by the South Central-Southwest (8.0 percent); trans-Canada, intra-Southeast, and Midwest-Southwest (6.7 percent, 6.5 percent, and 5.6 percent respectively); and Southeast-Southwest (2.0 percent). Of the top seven markets, only one reported a decline, with the Midwest-Northwest dropping 4.8 percent for its fourth consecutive quarterly loss.