AAR noted only eight of the 20 carload commodity groups it measures posted increases compared with the same week in 2011. Gaining groups included petroleum products, up 54.2%, motor vehicles and equipment, up 16.3%, and primary forest products, up 14.8%. Among declining commodity groups were metallic ores, down 15.8%, grain, down 13.4%, and nonmetallic minerals, down 12.4%.

Weekly carload volume on Eastern railroads was down 4.5% compared with the same week last year. In the West, weekly carload volume was down 4.1% compared with the same week in 2011, AAR said.

Canadian freight carload volume moved up 2.8% compared with the same week last year, while Canadian intermodal volume did better, up 9.2%. Mexican freight carload volume also advanced, up 5.9% for the week, while Mexican intermodal volume rose 18.9%.

Combined North American freight carload volume for the first 46 weeks of 2012 on 13 reporting U.S., Canadian, and Mexican railroads was down 1.9% when measured against the comparable period in 2011. Combined intermodal volume was up 4.5%.