Latest data from the Association of American Railroads highlighted mixed results for the year as coal dragged total rail volume down 3% to 14.7 million carloads and total intermodal traffic increased 3% to 12.3 million containers and trailers.

Coal was the commodity showing the largest falls, down about 700,000 carloads.

The biggest gainers were petroleum products, increasing traffic 46% and motor vehicles and equipment, up 16.5%.

“Coal and grain typically account for around half of US rail carloads, so when they’re down, chances are good that overall rail carloads are down too, as we saw in 2012,” AAR senior vice president John Gray said.

“That said, a number of key rail carload categories showed solid improvement in 2012, including categories like autos and lumber that are most highly correlated with economic growth.”

Rail traffic for coal in Mexico was down 15% on 2011, but Canada increased its coal traffic 5% to 449,000 carloads.

This brought total North American shipments to just under 6.5 million coal carloads for the year, a 10% drop on 2011.