Q: High-speed trains have been in the news recently. I love modern trains, and those who share this view cite financial savings and pollution prevention. Others wonder if it is financially or ecologically sensible to run a line that distance. When, if ever, would a financial break-even point come? What would be the carbon debt to construct such a train line? —Asked by Denny Brown, '79, Boulder, Colo.
Imagine that someone asked you to determine the CO2 emissions from a steel train track. Although you would assess the track's entire life cycle, you might assume that the majority of the impact would come from the manufacture of the steel, and so you develop a diagram like this:
Now imagine that you have to do this not only for the train tracks, but also the train itself, the stations at which it will stop, the parking lots its passengers will use, the fuel that moves it along the rails, and so on. Then, because alternatives play a major role in whether this train is the best transportation option for the environment, you must also do a similar analysis for cars, airplanes and heavy-rail transit. For nearly every step in a life cycle assessment, authors have to make innumerable decisions based on the best available information. Because of this, life cycle assessments are not 100-percent accurate and different assumptions may lead two researchers to get wildly different results. Nevertheless, LCAs are important in that they give us a more holistic understanding of the environmental impacts of our decisions.
So what?
You might be wondering why I belabored that point. The use (or disuse) of life cycle analyses can have big impacts on the decisions made by voters and our government. Let's stick with the example of California's high-speed rail project. In 2008 California voters approved funding for a high-speed rail system stretching over 800 miles from the Bay Area to Los Angeles. It was and is advertised as a "safer, cleaner and more efficient" [option] than flying or driving—creating jobs and new opportunity all along the way.
We learned in the Essential Answer that the "cleaner and more efficient" component of this statement is actually quite complicated. But what this claim is likely based on is an assessment of the so-called tailpipe emissions that look only at the emissions from the end result: in this case, the train's operation. If we combine that with the number of passengers per vehicle, we get a graph that looks like this:
Note the two train columns on the left and how drastically different the end impacts are between 100 or 10 percent occupancy levels.
What can we do to make trains the greenest transportation method?
What this study tells us is that we have to do some work to make trains the most environmentally friendly option. The authors emphasize two actions: choosing eco-friendly construction methods and keeping trains full.
If we look back at the above graph showing the life cycle emissions and energy use of high-speed rail, the two biggest impact areas are vehicle use and infrastructure construction. Let's think about the reasons vehicle use might have such a big impact. For one, like electric cars, these high-speed trains get their energy not from oil, but from electricity. This is a good thing for both our wallets and national security because electricity is generally cheaper than oil, and switching away from oil sends less money to unstable regions. But almost half of U.S.-generated electricity comes from coal, the dirtiest fossil fuel and a leading contributor to climate change. In short, high-speed rail run on coal-generated electricity is not much better for the climate than cars or airplanes.
Luckily, we have started to think about how we can use clean energy for high-speed rail. As it turns out, it is not cost or availability but institutional issues that are the limiting factor. If high-speed trains traveling through multiple counties and states wanted to have 100-percent renewable energy, they would need cooperation from the numerous local utility companies along the way.
Greening train infrastructure is less logistically complicated than greening train energy. What's more, it is often very cost effective. For example, the train platforms would likely be concrete, which is an extremely energy intensive material. Luckily, there are concrete alternatives, such as fly ash and blast furnace slag, which are industrial byproducts normally sent to the landfill. Choosing these more eco-friendly materials can have a big positive impact on a high-speed rail system's environmental chops.
Still, it is ultimately you who will contribute most to making high speed rail the greenest transportation option. The easiest way to do this is to simply make the decision to take it instead of flying or driving to your destination. This will reduce the per-person impacts of the train while also decreasing emissions from other types of transport. In the graph below, you can see that, especially in California, the trains will result in fewer emissions—but only if people choose it over other transportation options as often as possible.
This graph shows emissions saved when people shift to taking high speed rail from other types of transportation. In California, the amount save annually is almost twice the annual emissions of the high speed rail. Source: Center for Clean Air and the Center for Neighborhood Technology.
Other benefits of trains
This is an environmental advice column, but introducing networks of high-speed trains throughout the United States will have more than just energy impacts. So far, the federal government has allocated $8 billion from the Recovery and Reinvestment Act to developing high-speed rail. California anticipates spending $45 billion on its corridor. Is it worth it?
We've talked about the potential emissions benefits, but it is also important to consider that if we don't expand high speed rail as demand for long distance travel increases, the next best option would be to increase infrastructure for cars and planes. This is bad for the budget because it means millions of dollars spent building more highways and airports. And because cars and airplanes are big polluters, this would also be bad for the planet. Additional rail benefits might be the creation of "exurbs" near stations that could revitalize communities and depressed economies. Finally, constructing, running, and maintaining massive rail lines will create many more much needed jobs than will a new highway.
So whether you love trains, want a cleaner environment or just want a faster, more convenient way to travel, high-speed rail has the potential to deliver it all. Still, it's up to all of us to make sure we get the infrastructure improvements we deserve, so support the initiative and get excited about the high-speed rail coming to your state soon!
Bethany Wylie plans to receive her master’s in Earth Systems in 2011.
