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The Quebec town of Lac-Mégantic , with 13 people confirmed dead and about 40 still unaccounted for, after a train laden with crude oil slipped its brakes, derailed and exploded on 6 July. The catastrophe has already touched off over whether the US should permit the construction of the Keystone XL pipeline – which would transport oil from Canada’s tar sands to US refineries on the Gulf of Mexico.

asked The New York Times, before quoting one environmentalist as saying there was no conclusive research.

In fact, there are some solid numbers to go from, but they paint a complex picture. First, to make a fair comparison, you have to correct the numbers to account for the amount of oil involved and the distance it travelled. According to an , a pro-business think-tank in New York City, pipelines caused just 0.01 injuries per billion tonne-kilometre of oil and petroleum products transported between 2005 and 2009, compared with 0.38 for transport by rail.

Safety vs environment

The number of spills also favours pipelines, which do not burst as often as trains get into accidents. But in terms of the amount of oil and petroleum products spilled, the Manhattan Institute found pipelines outpaced rail transport. Between 2005 and 2009, pipelines spilled 62,400 litres per billion tonne-kilometre versus just 19,400 for rail.

Other groups have come to similar conclusions. “For the safety of humans, it looks like pipelines are better than rail,” agrees Carl Weimer, executive director of the in Bellingham, Washington, a public-safety advocacy group formed after a . But when a pipeline ruptures, he notes, the spills are typically much larger than from rail accidents.

The Manhattan Institute makes no secret of its support for the Keystone XL pipeline, and its report stressed human safety. “What is paramount in our society is the value of a human life,” argues , formerly chief economist with the US Department of Labor.

Weighing the relative importance of human versus environmental safety is just one aspect of the looming decision currently facing US president Barack Obama’s administration over whether to approve the Keystone XL pipeline.

Also hotly debated is how much oil from Canada’s tar sands will end up being moved by rail if the pipeline is not built. In March, the that if the pipeline was dropped then rail transport would expand to transport the same amount of oil that the pipeline would have carried. But the .