Intermodal shipments grew 4.7% in the third quarter as companies stepped up imports ahead of promised U.S. tariffs on foreign goods and domestic shippers shifted from highway to rail in response to rising freight rates and constraints on truck capacity.

One year into operations of the expanded Panama Canal, the freight transportation world has witnessed leviathan containerships, gargantuan land-based cranes and dredging projects along the U.S. East and Gulf Coasts, but intermodal shipping professionals say it’s too early to quantify the precise impact of the massive infrastructure project.