When I was in San Francisco in October, I met Chava Kronenberg, a bay area transportation planner and Metro Boston native. During our conversation she commented Boston’s quite extensive alternative transportation profile is often overlooked in national discussions. Instead, usual suspects like Portland, Oregon get all the credit for their green transportation systems. I decided to take a look at several transportation metrics to see just how green Boston was among big cities. Could it be the greenest city in America, as she claimed?

The three measures I chose were the overall percentage of workers using transit, bikes, and walking to work. I limited the analysis to the largest 30 “places” in the U.S. Census and used data from the 2006-2008 American Community Survey. Technically this is sample data, but I did not calculate margins of errors since for large cities they are generally small. Also, there’s an extensive and heated debate about exactly how green transit is. Most studies I’ve seen conclude busy buses or trains emit less pollution (including CO2) per passenger than private vehicles, but I won’t wade into the debate here. Here’s what I found.

Transit
For overall transit ridership to work, New York City (55%) and Washington, D.C. (37%) were winners, with Boston in third at 32% with San Francisco (32%) and Chicago (26%) rounding out the top five. Since this metric is for the center city only, I think Boston’s getting a bit short shrift. The region’s truly expansive commuter rail system (it goes all the way to Rhode Island — see below) carries an average of over 138,000 riders a day, more than all but two other similar systems in the nation — New York and Chicago. (Source: APTA ridership report (PDF))

Biking
What about zero-pollution biking? On this measure, the top five are Portland (4.7%), Seattle (2.5%), San Francisco (2.5%), and D.C. (2%) (which launched a bike-sharing system in 2008) and Denver (1.7%). Boston is only a few slots down at #7 with 1.2%. However, the city only recently saw the light and began pursuing bicycle planning aggressively. In fact, in the past it has been named one of the least bicycle-friendly cities in the U.S., although despite this bad reputation ranks way above dozens of other large cities.

The city’s 2009 State of the Hub report (PDF) reports 15 new miles of bike lanes (up from 0 in 2007), 500 new bike racks, a new bike map, and plans for a new bike sharing system moving forward. I should note plenty of smaller cities have larger shares of bike commuters. If Minneapolis were on the list, it would rank second with 3.5% of its commuters biking to work. If it were included, Boston’s neighbor Cambridge would be 5.8%, easily topping Portland.

Walking
Walking is another green mode available to most travelers, often overlooked for more exciting trains and bike facilities. However, making a city walkable can be tricky, as it depends on a subtle combination of good public facilities, urban design and density, and mixed land uses. On this measure, Boston tops the list at 14%, with Washington, D.C. just behind at 11.7%, and the rest of the top five New York (10.1%), San Francisco (9.52%), and Seattle (8.6%). It turns out some of the factors that make Boston such a bad city to bicycle — congested streets and a dense street grid — make it excellent for walking. Walking is so popular the city boasts an active walking advocacy organization — WalkBoston — and extensive trail networks along the harbor and through parks.

Next, I created a composite score for all three indicators. For each indicators, the cities were ranked with 1 going to the city with the highest (best) value and 30 to the worst. I then added the rankings together, weighing each equally. The lower the resulting score, the better. This score gauges the diversity of the mix, and isn’t an objective measure of pollution output. In this measure, Washington, D.C. ranks first with a score of 8, San Francisco and Boston tie for 2nd at 11, and Seattle fourth with a score of 15. New York, strong on transit and walking, falls to an overall place of seventh due to it’s low biking score (16th with just 0.7% of commuters reporting biking).

What can we conclude from this simple comparison? First, as Chava suspected some very bike friendly places like Portland may not have many transit riders or walkers. Any evaluation that stresses diversity, like this one, will rank them lower than older cities with well-developed transit and street networks. And although it comes as no surprise to me, Washington, D.C.’s high ranking may surprise some. Indeed, it is the result of many factors: excellent “bones” in a good street and sidewalk grid, decisions by city leaders in the 60s and 70s to stop as many highways as possible and invest heavily in transit, lots of government-related jobs concentrated downtown, and a city government aggressively pursuing improvements to bicycle, walking, and transit infrastructure in recent years.

Finally, I think Boston’s high walking score and surprisingly high biking statistics (despite little infrastructure and bad weather) show it is somewhat underrated. But is it the greenest city in America? That’s for you to decide.