Nati Harnik, File, Associated Press
FILE - This Oct. 13, 2010, file photo shows the Sandhills near Mills, Neb., an environmentally sensitive area which TransCanada had planned to build a pipeline through to transport crude oil from Canada to the Gulf Coast. The company said Wednesday, Sept. 5, 2012, it has revised the Keystone XL pipeline route to minimize the potential impact on the Sandhills region and avoids two small city well fields.

The calamity of a train derailment in Quebec Province is casting new light on the debate over the controversial Keystone pipeline project, bringing into the conversation some real-world public safety concerns. Should Keystone not be built, energy experts say the same number of barrels of Canadian crude oil might instead be loaded onto trains for transport through America's heartland to Gulf Coast refineries.

Given the devastation wrought on the picturesque town of Lac-Megantic, the prospect of significant increases in oil transport by rail should certainly be taken into consideration as authorities decide whether to give Keystone the go-ahead.

Pipeline opponents argue the extraction and refining of tar sands comes with significant environmental risks, particularly in the form of increased greenhouse gas emissions. These short-sighted concerns are premised on the notion that without the pipeline, demand for tar sands oil would diminish and the rate of extraction, and, therefore, emissions would be lower.

Economic realities, however, undermine the premise. The vast reserves of oil sands, in Canada and elsewhere, can be brought to market at costs competitive with other sources and, therefore, the forces of supply and demand will conspire to take tar sands crude to the Gulf Coast anyway, or to China or some other part of the world where demand exists. If much of the crude will enter the United States regardless, the question becomes which way is best to transport it?

It is difficult to compare rates of pipeline failures with rates of train accidents, but a factor that shouldn't be overlooked is that without Keystone, experts suspect the rate of oil transport by train might increase substantially. A report by the U.S. State Department in March suggests trains will be carrying up to 250,000 barrels of Canadian oil to the Gulf Coast every day by the end of this year. The 1,200-mile Keystone pipeline would be capable of transporting 800,000 barrels a day. Over time, experts hypothesize that minus a pipeline alternative, the costs of sending more trains south with oil aboard would be more attractive economically.

There is, of course, the macro argument that energy policy should seek to deter the development of "dirty" sources in favor of clean and renewable energy. But such a transition must come gradually and be propelled mainly by market forces, which would be more efficient and carry less collateral damage than any government campaign to strong-arm oil users onto a different diet.

In the meantime, it's important that the exploration, extraction, transport and refining of oil be done safely and in an environmentally sound manner. Seeing to that is government's responsibility.

As Washington contemplates approval of the Keystone project, it needs to view the issue of pumping heavy crude through a pipeline in comparison with the risks of the alternative. Last weekend's calamity puts those risks in sharper focus.