Q: Although my partner and I live in Memphis, a city that’s sans subway — no, I don’t have to worry about going without when I get a hankering for a Five Dollar Footlong we make do just fine with a combination of city buses, bikes and a shared car. Even though our hometown is without a rapid transit system, we frequently travel and always “go underground” to check out the metro system wherever we may be. In fact, we’ve ridden so many from the "L" to the "T" to an assortment of German "U’s" that we’ve begun to fancy ourselves as buffs when it comes to trains, trams and trolleys. My personal favorites? It’s a close tie between the spectacularly scenic Wuppertal Schwebebahn and the over-the-top, ornate Moscow Metro.

Throughout all of our international subway sampling, it’s become obvious that rapid transit is the environmentally preferable way to get from point A to point B. But my question for you: Are there any metro systems out there that go above and beyond on the eco-friendly front?

Looking to ride the “green” line,

Travis Memphis, Tenn.

A: Hey Travis,

Great question. This is something that I often think about myself as I stand waiting in the bowels of New York City’s rank, garbage-strewn and increasingly expensive subway system (please don’t get me started on this or I’ll never stop ranting). My patronage of rapid transit is an inherently green act but what are subway, metro and monorail systems around the world doing, if anything, to up the eco-friendly ante?

Well, as it turns out, plenty. Even the MTA, the much-reviled organization that runs NYC’s subway, has a few notable sustainability initiatives on the energy-efficiency, water and waste fronts. However, I’m most impressed/surprised by the MTA’s green building efforts, which include the LEED certified Corona Maintenance Facility in Queens and Coney Island’s Stillwell Avenue Terminal, which boasts a rooftop solar array that helps to power the station. Who knew? This disgruntled straphanger certainly didn’t.

The New York City Subway System, like numerous other metro systems such as London’s Tube, the Copenhagen Metro and the Delhi Metro, already harnesses the power of regenerative braking to some degree. But SEPTA, the organization behind Philadelphia’s subway system, is taking the energy-saving potential of regen braking to a whole new level with a $1.5 million pilot program that involves installing massive batteries at substations along the busy Market-Frankford line. The batteries will store and distribute kinetic energy that’s generated by the braking of trains. The energy will be converted to electricity and either be used to help trains accelerate, stored or — most remarkably — sold to local utilities and returned to Philly’s power grid.

Across the pond in the famed Paris Metro, the heat generated by sweaty straphangers, not train braking systems, will be funneled above ground and used to supply energy to apartments in a low-income housing project that’s located directly above a Metro station on Rue Beaubourg. This concept may seem wild but it’s essentially just a nifty new spin on ages-old geothermal heating and cooling technology. And while I’m on the topic of clean energy, it’s been reported that Spain’s Bilbao Metro system was completely powered by renewable energy in 2008, preventing 46,000 metrics tons of CO2 from entering the atmosphere.

From highly efficient trains in Oslo to a metro station in Madrid that’s cooled by geothermal technology, plenty of other rapid transit systems across the world are dedicated to making getting around within a city even greener.

Also Travis, you mentioned your favorite subway systems that you’ve had the pleasure of riding. I’ve been on a few different metro systems in my time including a few mentioned above, but it’s my experiences on the Prague Metro that will always stay with me. Ukončete, prosím, výstup a nástup, dveře se zavírají.

— Matt

Photo: Susan NYC/Flickr

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

Are some subways greener than others?
Matt Hickman finds some neat innovations around the world -- and even in New York City, much as he hates to admit it.