Intermodal traffic dipped 0.2% last week from a year ago, the Association of American Railroads reported.
Container traffic increased 0.6% to 165,900 units, but trailer traffic dropped 4.4%, to 26,719 units.
Railroad carloads excluding intermodal fell 3.2% for the week ended Saturday, to 245,574 units, AAR said in its weekly report.
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.