By Colin Kellaher 



  North American rail traffic fell 9.2% last week, reversing gains from a week earlier amid a shift in timing of the Labor Day holiday in the U.S., data from the Association of American Railroads showed. 


  Carload volume fell 12.7% for the week ended Sept. 12 on a dozen reporting U.S., Canadian and Mexican railroads, while intermodal traffic fell 5.9%, the trade group said Wednesday. 


  In the week ended Sept. 5, North American rail traffic rose 7.6%. For the first 37 weeks of the year, North American traffic is down 10.5%. 


  The AAR said U.S. rail traffic fell 9.9% last week, with carloads down 15.2% and the volume of intermodal containers and trailers off 5%. U.S. rail traffic is now down 11.2% for the year to date, the AAR said, compared with a decline of 11.3% reported a week ago. 


  Canadian rail traffic fell 5.2% last week amid a 5% decline in carloads and a 5.5% drop in intermodal units. Canadian rail traffic is down 8.1% for the first 37 weeks of the year. 


  Mexican rail traffic slid 15.4% for the week, as carloads fell 11.6% and intermodal units tumbled 19.1%. Mexican rail traffic is down 9.6% for the year so far, the AAR said. 


  Write to Colin Kellaher at colin.kellaher@wsj.com