The Association of American Railroads said total carloads for the week ending July 13 was down 3.1 percent to 277,132 carloads compared to the same week in 2012.
Six of the commodity groups delivered by rail posted increases for the week. Petroleum and petroleum products led the way with a 19.7 percent increase year-on-year, the AAR said Thursday.
Rail shipments of oil products in the United States have increased in response to the rise in oil production. Advancements in drilling technology have led to oil production increases in states like North Dakota, where record-breaking production has outstripped existing pipeline capacity.
The rail-versus-pipeline debate increased in the wake of the deadly July 6 train derailment in Quebec. Crude oil was released from tankers during a derailment that left dozens of people dead and at least 40 buildings destroyed.
Pipeline supporters say its a safer way to deliver oil though spill volumes are far greater when they do occur.
AAR reports total rail volumes for the first 28 weeks of the year are down 1.4 percent year-on-year.