High Voltage - by oskay on Flickr

The fact that most rail transit systems operate via electric power is usually listed as a net benefit in terms of energy efficiency.  Not only is transit hailed as an inherently more efficient mode (more persons per vehicle, steel wheels on steel rails – as opposed to rubber tires on asphalt, etc), the fact that it’s using electricity is another environmental benefit over gas guzzling cars.  Yonah Freemark says not so fast, however.

Eurostar’s example is a case in point: transportation systems relying on electricity can be dirty or clean, all depending on where the power is coming from. This point is unfortunately lost on most alternative transportation activists, who cite efficiency to support the claimed ecological advantages of using transit instead of automobiles. Yet efficiency means little when the electricity used is being produced by carbon-generating plants.

Now this is undoubtedly true – where the electricity comes from matters.  However, that’s the beauty of electricity and transit systems that use it.  Electricity can be produced in any number of ways, some more sustainable than others.  The key difference, however, is one of scope.  Electricity generation and greenhouse gas emissions are a whole different piece of the pie, dealing with every aspect of energy policy.

Light rail running on electricity may seem clean, because the local point emissions — in the city — are nonexistent, especially as compared to diesel-spewing buses. But if the necessary power is being generated at coal-based plants, the global effect is negative, making some transit systems less environmentally sensitive in terms of per passenger emissions than many automobiles.

Yonah’s referencing the fact that on a pure BTU per passenger basis, rail isn’t that much more efficient than a Prius.  What this measure misses, however, is the secondary effects of transit.  Congestion reduction alone saves tons of fuel from idling traffic, not to mention the savings of switching trips or eliminating them all together.  Additionally, the changes in land use that rail transit enables allows more efficient transportation – walking trips, shorter trips due to neighborhood retail (and improved accessibility), and so on.

Where electrically powered rail transit vehicles have an advantage is in their applicability.  The infrastructure (in most urban rail transit systems) is in place.  The technology is proven.  The same can’t be said of electric cars.  They’ll face the same kind of issues with the cleanliness of the electricity they use, whether they’re plug-in hybrids or pure electric vehicles – and they won’t solve congestion issues or address the new residential demand from cars plugging in while parked in the garage.

Still, these are nitpicking Yonah’s general argument and final conclusion:

The point, then, is that to suggest that transit is ecologically sensitive is more accurate when the source of that transportation’s electricity is carbon-free or at least carbon-reduced. Proponents of transportation alternatives must also be strong advocates of the remaking of our electricity production system.

Transit alone isn’t the silver bullet.  It can only be one part of the puzzle.   Though I think it’s a larger piece of the puzzle than this post would imply, we must remember how that piece fits into the whole energy system.