Rail and intermodal traffic both declined for the week ended Saturday compared with a year ago, the Association of American Railroads said.
Intermodal traffic fell 1.6%, led by a 1.8% drop in container traffic to 189,183 units. Trailers fell 0.8% to 50,898 units.
For the first eight months of the year, U.S. intermodal traffic was down 2.9%, to 7,828,312 units from a year ago.
Overall rail traffic dipped 0.3% for the week, to 342,040 carloads from a year ago, the group 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.