Click here to write a Letter to the Editor. Fourth-quarter intermodal volume rose 0.6% from the same period a year earlier, capping off a fifth straight year of growth, the Intermodal Association of North America said.Volume reached 3.58 million shipments, IANA said in its quarterly report released this week. The level was the third-highest on record, led only by the second and third quarters of last year.Domestic container traffic rose 4.9% in the quarter, while trailers fell 15%, in part because railroads were converting freight to double-stack containers. International traffic rose 4.3%, IANA said.Meanwhile, intermodal volume for the week ended Feb. 3 dipped 2.4% to 226,472 trailers and containers, the Association of American Railroads said Thursday.Container traffic edged up 0.4%, while trailers plunged 10.7%, AAR said.AAR reported 317,887 rail carloads, down 7.2%, while total rail freight volume was 32.3 billion ton-miles, down 6.1% from a year earlier.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.