If you read beyond the dubious headlines today, “Think Twice About ‘Green’ Transport, Say Scientists” and “Train Can Be Worse for Climate than Plane,” you’ll find an interesting study that suggests policy makers go beyond tailpipe emissions when calculating the carbon impacts of planes, trains, buses, and cars. University of California-Berkeley researchers attempted to also account for greenhouse gases released when building the vehicles, generating fuel to run them and for building and maintaining the infrastructure they use.
Among the findings: including these additional sources of pollution in a life-cycle assessment (which is no simple task) more than doubles the greenhouse gas emissions of train travel, with its stations, miles of track, lit parking lots and escalators. Proportionally, they add less to the carbon footprint of cars and planes.
The study also found electric cars and trains have hidden emissions if the electricity they run on is generated by burning coal and other fossil fuels. And when it comes to mass transit, how many passengers are on board matters.
It isn’t a shocker that the researchers found that Boston’s rail system produces more greenhouse gas emissions because of the coal-based electricity it uses. By comparison San Francisco’s system produces fewer greenhouse gas emissions because the electricity is cleaner, mostly from non-coal-burning sources.
The researchers are recommending that those sources be factored in so that eventually they can be changed. While cutting tailpipe pollution and increasing fuel efficiency is important, a more holistic approach to reducing transportation greenhouse gas emissions would make rail stations and airports more energy efficient and look to grow renewable energy sources.
The study also points out that the number of passengers on board is important. A nearly empty diesel-burning bus, for instance, may be less energy efficient than a full SUV. But 60 people on a bus produce far fewer emissions than 60 people driving 60 SUVs. It’s right in the abstract: “occupancy can easily change the relative performance of modes.”
So when deciding what mode of transportation to take and how much CO2 it emits, the general rule of thumb is to walk, bike, or catch a ride on something already going in your direction, including buses and trains.