Intermodal traffic rose 5.7% last week compared with the same week a year ago, the Association of American Railroads reported.
Traffic increased to 223,034 units for the week ended Saturday, AAR said in its weekly report.
Trailers rose 5.6% to 34,309 units, while containers gained 5.8% to 188,725 units.
Railroad carloads excluding intermodal showed a 1.9% gain to 299,903 carloads, AAR said.
Railroad volume is considered an important economic indicator. Intermodal traffic, which tends to be higher-valued merchandise than bulk commodities, uses trains for the long haul and trucks for the shorter distance at either end of the trip.