How Clean Is Your Commute?


A new report from Transportation Alternatives comparing carbon emissions for NYC transportation modes finds that drivers account for 60 percent of the city’s transportation-related CO2, while accounting for just 31 percent of all commuting trips.

"Rolling Carbon: Greenhouse Gas Emissions from Commuting in New York City" [PDF] reveals that the average New York City commute generates about seven pounds of carbon dioxide per round-trip, for a total of 1,750 pounds of CO2 annually. Though this ranks us among the "greenest" US commuters in the aggregate, the report notes that individual impacts vary widely, depending on mode and distance. To that end, "Rolling Carbon" breaks down per-mile emissions for public and private conveyance, from Escalades, taxicabs and Priuses to trains, buses and, of course, bikes and feet.

Other report findings include:

  • Driving alone causes the emission of about five times the amount of CO2 (over 4,000 pounds per year) as is caused by taking the subway (about 820 pounds per year).
  • If just 5% of all people commuting by private car or taxi switched to transit, walking or cycling, the result would be a decrease of 150 million pounds of CO2 emissions per year — the equivalent of planting trees on an area 1.3 times the size of Manhattan.

Accompanying the report is a new killer app: features a personalized Carbon Calculator for New Yorkers to determine emission levels generated by their commutes, and how many annual tree plantings would be needed to offset the trip. As illustrated by the chart above, pedestrians, cyclists and skaters are in the clear.

  • Ann

    Guess I’m a jerk for riding the bus instead of driving a Prius!

  • graham

    If that graph was pounds CO2 squared per passenger mile, you would feel much less like a jerk.

  • Shemp

    If the transit calculations assign all the emissions per vehicle to each rider, this thing is pretty useless for NYC.

  • In case this isn’t totally obvious, the Prius’s outperformance of the bus is misleading.

    Each Prius on the road adds to congestion, which makes all the non-hybrid cars on the street at the same time burn more fuel. It is still “greener” to ride a bus than to drive your own Prius.

  • rlb

    The key difference between the bus and the prius, is that the bus exists with or without your ridership. In that sense, riding the bus adds nothing to the total CO2 emitted. In fact, switching from prius to bus lowers the lbs. per mile of bus travel by a puny amount. That is until the ridership of the bus exceeds the capacity, requiring additional buses.

  • Ian Turner

    My guess is that the Prius CO2 numbers don’t include the (high) cost of the energy required to produce the car’s limited-life battery. Logically, CO2 costs to make a vehicle should be amortized over the number of miles you can expect to get in the vehicle’s lifetime.

    If hybrids do fare well in this analysis, then we should switch the bus fleet over to hybrid, which will correct the graph somewhat.

    Also, although New York driving may be one of the best circumstances for hybrid technology, the published Prius MPG numbers are rather optimistic; I gather that Toyota tuned their energy transfer system to favor the government test.

  • Boris

    I think the key thing to understand in the Prius-bus comparison is average CO2 usage per person. Assuming on average a Prius holds 2 people while traveling, a Prius-rider generates about .4/2 = .2 lbs of CO2/mile. Assuming an average bus load of 10 people, each bus-rider generates .5/10 = .02 lbs of CO2/mile. Given these numbers, a bus is 10 times as clean as a Prius.

  • Boris

    Strike my last comment. I should’ve read the paper first. Bus numbers are already per passenger-mile, so a Prius is, indeed, cleaner (except in the way rlb points out).

  • Another major difference between the bus and Prius: buses tend to promote transit-oriented development while cars tend to promote sprawl.

    I have heard that the rule of thumb is that, for every trip you shift from a car to a bus, you also shift 3 additional trips from car to foot, because of the sort of development that buses and cars promote. Take this into account, and the bus is much greener than the Prius.

  • Shemp

    Our buses must really suck if a solo driver in a hybrid has a smaller pure-emissions footprint than an individual on a bus with 30-50 people on it.

  • JP

    If the bus figure is correct, maybe we should be looking into developing clean bus technology. How about instead of $50 billion in guaranteed loans for auto makers, we guarantee some loans for a start-up that will invest in designing and manufacturing an electric bus.

    And what about those buses in San Francisco that run on the overhead wire? The technology for electric must be out there, we would just need the power source?

  • Ian Turner

    Lots of cities have an overhead catenary system, but it’s hugely expensive to maintain. If we’re going to invest in additional infrastructure in NYC, light rail and subway improvements are probably a bigger win.

  • People don’t breathe out any CO2 when they walk or bike?

  • Josh, we also produce methane, which the report clearly did not take into account.

    A disappointing set of facts in the report is page 31, which gives the emissions per passenger-mile of the different types of buses. Diesel is 0.52 pounds of CO2 per passenger/mile, hybrids are 0.42 and CNG are 0.58.

    Of course, emissions are only part of the story. Fuel efficiency is another. From a fuel efficiency standpoint, it looks like it’s still a good idea for the MTA to continue converting the bus fleet to hybrids, and to promote BRT. As the report says:

    While this report addresses CO2 emissions specifically, modal shifts away from cars and onto public and non-motorized transportation will confer myriad additional benefits: improved air quality, reduced congestion, safer streets, and a more active, healthier population. As the City considers policies and programs promoting modal shifts (congestion pricing, transit, bicycling and walking improvements, etc.), the CO2 emissions reductions quantified here should be considered as just one element of the overall public benefit.

  • Niccolo Machiavelli

    Interesting watching us devour ourselves as to how a Prius can possibly be greener than a bus. Let me further tangle the discussion. All of this is related to load factors as well, so as in many things transportation, capacity utilization is the most important factor (closely related to residential densities and a further argument against down-zoning in Brooklyn and Queens). Also bus loads include the long periods of the evening when buses run around basically empty (a sight for sore eyes though they may be after a long night of drinking). So, full buses will be much, much more efficient than full Prius’. Stringing, powering and maintaining the wires for trolley buses does have a substantial capital cost but nothing like a light rail system. And there are other capital savings as well. Many cities run those systems, check out Boston’s next time you go to a Red Sox playoff game.
    My point is that this is not new tech or even high tech but just tech and are common worldwide, clearly something that could easily be applied in the MTA NJT and PA market were there sufficient will to limit emissions so.

  • Quite right, Nico. You also reminded me that I was going to ask if anyone can tell me why the MTA doesn’t use minibuses (or microbuses) on its less-traveled routes. In addition to being more efficient and polluting less, microbuses would be a lot more maneuverable on some narrow residential streets, and might engender less of that Glendale-type NIMBY reaction. It would be nice to get a sense of how much it would effect emissions if every route that had less than 20 passengers at any given time used microbuses.

  • Ian Turner

    A lot of private bus companies will run commuter vans as a backup or late-night service. I never understood why public bus companies in the US don’t do this; my guess is it has something to do with federal funding; you’re not a transit agency unless your buses are at least 30′ long or something.

    Transit agencies in other (less urban) parts of the country run these huge buses all over the place with 1-2 (or zero!) passengers. It’s pretty ridiculous.

  • The carbon footprint of cycling comes from the additional food you have to eat. See here.

  • Niccolo Machiavelli

    The answer of course Ian is they don’t. The late night service schedule run by the MTA is pretty much unique throughout the country and certainly no private, profit making companies are paying people to drive around empty buses however small.

  • iso

    If parking and the space it requires were taken into account, both the bus and the taxi would be far, far “greener” than the Prius!

  • Larry Littlefield

    The price has it right — not only have buses been worse for the environment than Priuses, they have been almost as bad as SUVs.

    But that changes if more people ride them.

    Thus, for those who had ECON 101, is the difference between the AVERAGE carbon emissions and the MARGINAL carbon emissions. Until they reach overload, mass transit systems have near-zero marginal costs and emissions.

  • Joe Common Sense

    This is another case of another very poorly written blog, poorly performed research, and idiotic statistics that don’t show the whole picture. A prius holds, say 5 people – MAX and a bus upwards of 60 to 80 people, depending on the type of bus. Work a per passenger mile figure into the graphic.

  • There is a per passenger mile graphic in the idiotic report linked from the very poorly written blog. It’s on page 12.

  • Jeffrey W. Baker

    But the per-passenger-mile basis is a trap. It assumes that longer, sprawlier trips are more highly valued. The denominator should be passenger-trip, not passenger-mile.

  • Small City Transit Manager

    There a few problems with minibuses. Federal funding does not allow you to buy more buses than you actually need. Your need is based on your peak requirement. So you end up running what you have, which are buses big enough to meet your peak ridership during the day. If you do run smaller buses then you can easily run into capacity constraints. Load a wheelchair on to a minibus and your seating goes from, say, 19 to 12 or 14. Small buses often only get marginal improvements in fuel economy. A Ford E-450 “cutaway” only gets 7 to 8 MPG on suburban routes, so it would probably get around 5 or 6 on urban routes. Also, those big buses 35′ or 40′ are heavy duty transit buses that can withstand stop and go, and they have a lifetime of 12 years and 500,000 miles. Put the aforementioned cutaway into urban service and you’d be lucky to run it to 100,000 miles before it becomes expensive to maintain or downtime becomes an issue (despite what the Ford commercials tell you a 6.0L PowerStroke diesel is NOT heavy duty). So you end up replacing a minibus 3 or 4 times during the lifespan of a HD transit bus. From the fiscal standpoint, the most expensive cost of running a bus is the driver, and, in my experience at least, maintenance costs are very similar on a per mile basis.

    Minibuses do emit less CO2, but there are many more factors to consider. The intermediate step before fuel cell is either diesel-electric hybrid heavy duty bus (they get around 5 MPG versus a conventional diesel heavy duty bus getting around 2-3 MPG) or CNG.

  • Sorry, I forgot to close my link.

    Also, I’m usually a big fan of Streetsblog, including Brad’s contributions. My one bit of constructive criticism here: lots of people get confused about the various environmental and other impacts that mode choice can have. They especially confuse energy efficiency, petroleum dependency and emissions. I think this post would have been more informative if you’d pointed out, as the study did, that emissions are just one of the wide range of consequences. To put it in perspective.

  • Michael

    What if the whole lifecycle (mining, waste, production process etc) is weighed into the equation? Then I bet the bus is more efficient than the Prius…

  • This article omits a critical consideration. Transit represents embedded energy. Busses and trains run on schedules whether full or empty; the energy consumed is consistent and ever present and there is no choice in the matter. The driver of any vehicle, Prius or Escalade, makes a decision to operate that vehicle. That driver is not required to make its “rounds” as a bus or train is and thus the energy needed to operate that vehicle could be left unused by using transit, walking or riding a bike. And of course, this also ignores the land consumed to build roads and parking for all the cars. A prius uses roughly the same amount of space as Hummer.

  • Thomas Marchwinski

    I have some real problems with how these calculations were done. First of all, the NY reduction in speed maybe too low. Also, as acknowledged in the report, the fuel economy reported is not real world, so I think the Prius example overstates the MPG because of lower average spees, even lower then shown here.

    For Bus, a total annual riderrship number is used and then apportioned based on vehicle type VMT. The average of 16 persons per bus mile includes a lot of late night and weekend hours. Also, passenger average trip length using federal data is notoriously weak given small samples. Finally, the census data they quote is not real census data, because of data suppression a lot of data is lost. The average commuter rail trip of 11 miles is way off base, unless they are talking about only NYC residents commuting to NYC. Because of these issues, I think the Prius/Bus comparison is actually much closer then shown here.


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