Riding between New York and Boston last week on a comfortable and uncrowded Amtrak Acela train it dawned on me that my comfort came at a price. An uncrowded train meant Amtrak was not earning as much revenue as it might have from this run. Beyond that, I wondered, what of the environmental impact of my trip? Everyone knows that public transportation is greener than the private alternative. But what about a sparsely populated train? They are enormously heavy machines that consume most of their energy just moving themselves, before any passengers are added. When is a near-empty train worse for the environment than driving?
Just in time, James Kanter of the New York Times blog Green Inc. wrote about a recent academic study out of the University of California, Berkley that compares the environmental footprint of public transit, air travel and private car travel.
The focus of the article is on the need to take a full life-cycle approach when comparing the costs and benefits of those modes of travel. You have to consider not just the energy it takes to move a passenger one kilometer (the standard measure used for comparison). You also need to look at the energy and environmental impact of building the vehicles and the support infrastructure (including airports, runways, train stations and tracks).
The study found that “total life-cycle energy inputs and greenhouse gas emissions contribute an additional 63% for onroad, 155% for rail, and 31% for air systems over vehicle tailpipe operation.” In a nut shell, there is a steep environmental cost incurred even before any travel occurs, especially for rail and air travel.
The implication of this, according to the study is that, while improving the energy efficiency of transport is important, for modes like rail and air its also especially important to explore ways of reducing the environmental impact of the non-operational components such as infrastructure construction.
It also means that improving the occupancy rate of trains and airplanes has a greater impact on the economics and environmental footprint than it does in car travel. Indeed, the study showed that while at average occupancy rates,
train travel is always more environmentally benign, a sparsely populated train can actually use more energy and emit more greenhouse gases per passenger-kilometer than full automobile.
To me the policy implications are clear: beyond supporting research in more energy efficient public and air transit infrastructure, continue to support the use of existing public transit systems, a large portion of whose environmental costs are already sunk.
Do you agree? What are your thoughts?