AAR said 12 of the 20 carload commodity groups it measures posted increases compared with the same week in 2011, led by petroleum products, up 49.4%, motor vehicles and equipment, up 23.3%, and lumber and wood products, up 17.9%. Groups pacing declining commodities included nonmetallic minerals, down 16.3%, coal, down 16.1%, and coke, down 8.6%.

Canadian freight carload volume continued to ignore the trend of its U.S. counterpart, 6.6% compared with the same week last year. Canadian intermodal volume also increased, up 8.8%. Mexican freight carload fell 3.4% for the week ending May 19, but Mexican intermodal gained 13.4% compared with one year ago.

Combined North American freight carload volume for the first 20 weeks of 2012 on 13 reporting U.S., Canadian, and Mexican railroads was down 1.8% compared with the same point last year, while combined intermodal volume was up 4.2%.