How Much Can Bicycling Help Fight Climate Change? A Lot, If Cities Try

A new study from the Institute for Transportation and Development Policy attempts to measure the potential of bikes and e-bikes to reduce greenhouse gas emissions.

Buenos Aires has been ambitiously building out a network of well designed, separated bike infrastructure. If this kind of commitment were employed worldwide, the environmental and financial repercussions would be enormous. Photo: ITDP
Buenos Aires has been building out a network of protected bike infrastructure. If this kind of commitment were employed in cities worldwide, the climate benefits would be huge. Photo: ITDP

ITDP’s conclusion, in short: Bicycling could help cut carbon emissions from urban transportation 11 percent.

The authors calculated the carbon emissions reduction that could result if cities around the world make a strong, sustained commitment to promoting bicycle travel.

In a scenario where 14 percent of travel in the world’s cities is by bike or e-bike in 2050, carbon emissions from urban transportation would be 11 percent lower than a scenario where efforts to promote sustainable transportation sidestep bicycling.

The ITDP scenario calls for 11 percent of urban mileage by bike by 2030 before hitting 14 percent in 2050. For many big American cities where bicycling accounts for a small share of total travel, that may sound like a high bar — and that was part of the point. The ITDP targets will require a significant public policy commitment. But the goals are achievable and aren’t as daunting as they might seem, the authors say.

Already, ITDP estimates about 6 percent of miles traveled in world cities are by bike or e-bike. More than half of those bicycling miles, however, come from just a few countries, including Japan, China, the Netherlands, and Denmark.

In general, bicycling’s share of travel is flat or falling in developing countries. And in the U.S. and Canada, bicycling only accounts for about 1 percent of non-recreational trips.

Baseline world cycling rates. Graph: ITDP
Current bicycle mode share in selected countries. Chart: ITDP

Under the scenario described by ITDP, bicycling would rise to about 11 percent of miles traveled in American and Canadian cities by 2050. In countries like China where the rate is already above that level, it would be as high as 25 percent.

In order to achieve that level of cycling, cities around the world would need to make substantial changes to their policies and infrastructure, ITDP says, including:

  • Rapidly developing large-scale networks of bike infrastructure.
  • Implementing bike-share, with an emphasis on connections to transit.
  • Revising laws to protect cyclists and pedestrians.
  • Investing in walking and transit.
  • Coordinating regional land use planning with transportation investments.
  • Ending subsidies for driving, like parking minimums and fuel subsidies.
  • Instituting congestion pricing.
  • Dedicating driving fees to sustainable transportation.

The report builds on previous research from ITDP measuring the potential impact of dramatically expanding the use of sustainable transportation in U.S. cities. That study found shifting reliance from cars to bikes, buses and walking, could reduce emissions from transport in cities by 40 percent. The new report was undertaken after bike advocates in Europe and elsewhere responded that the previous study may have underestimated the share of trips that could be shifted to bicycling.

Factoring in the greater potential for mode shift to bikes, ITDP estimates that the total reduction in urban transportation emissions by 2050 could reach 50 percent if cities aggressively pursue policies to promote sustainable modes. The upcoming United Nations Climate Change Conference (COP 21) in Paris “provides an excellent opportunity to move global policy toward supporting this scenario,” ITDP concludes.

31 thoughts on How Much Can Bicycling Help Fight Climate Change? A Lot, If Cities Try

  1. How about this… convert one lane of every NYC boulevard, avenue, expressway and parkway to bicycles. Then legalize e-bikes. Pretty soon, New Yorkers will learn what REAL mobility looks like. It could even cut congestion in the remaining car lanes.

  2. Used to take the subway or walk everywhere; I was almost never in a car. Now I bike everywhere. Am I saving greenhouse gasses in any way now that I ride a bike? When I started bicycling, I tried to think of ways I was being eco friendly, but I couldn’t come up with anything.

  3. Such a move would be bold, but it is necessary. Major bike cities such as Gronigen or Utrecht did not become what they are today through modest improvements in bike infrastructure. They made consistent, radical decisions without bending over backwards to appease the motorists. Decades later, they are reaping the benefits.

  4. Exactly. Almost everyone I know who bikes mode shifted from bus not single occupancy cars. Last I heard our town was greatly increasing bus routes and frequencies so I’m not sure where the carbon reduction is happening.

  5. Per passenger-mile, the NY Subway is the most efficient public transport system in the USA. But it still requires as much energy as a single-occupant Toyota Prius. It emits less CO2 because some of its electricity is low-carbon (nuclear power). The typical bus is about as efficient as a single-occupancy Toyota Corolla, and gets all its energy from petroleum.

    Bicycles, on the other hand… the agricultural system producing FOOD used to power them is extremely inefficient; about 6X as much CO2 is emitted PRODUCING the food than you emit EATING it. When you take that into account, bicycles are less efficient than they at first seem (but still better than cars, buses or trains). Bikes are especially good if you can overlap your exercise and transportation needs; that’s food you would have had to eat anyway. You can also cut your food carbon footprint markedly by leaning vegetarian.

    E-bikes have the lowest operational carbon emissions of all because they use only a little more power than manual bikes, their power is generated efficiently, and it’s sometimes low-carbon.

    So the quick answer is… if you switched from peak-hour subway travel, AND you’re not biking too far, then you’re probably saving significant CO2 by making the switch. If you’re switching from off-peak or reverse-commute trains (i.e. ones that are empty), then you’re not reducing emissions, because those trains were going to run anyway. In places like NYC or SF, switching away from peak-hour subway travel also has the benefit of relieving an increasingly overcrowded system — and putting off the billions of dollars in capital improvements that would be needed to remedy the problem. Building out a protected bike lane on an existing Avenue costs a small fraction of a new subway line.

    “Last I heard our town was greatly increasing bus routes and frequencies so I’m not sure where the carbon reduction is happening.”

    Let me say it again… buses are no more efficient than a single-occupant Toyota Corolla. They will never lower your carbon footprint directly. They will only lower it if their use leads to decreased demand for travel (presumably be enabling higher densities, i.e. allowing construction on parking lots). Switching to public transport in and of itself will NEVER be a successful large-scale carbon reduction strategy.

  6. My commute has put this into focus. A large fraction of it is on high-quality bike routes, comparable to expressways — even parallel to major expressways. Then I get dumped on city streets and even a dirt path, while the expressways I’m parallel to continue along the way. It feels like driving in the 1970’s, before the Interstate Highway System was complete. Yes, it DOES take more time to navigate stop-and-go traffic than to stay on the go-and-go bike path — cruising on my e-bike at 20+ mph. Fixing the missing links would save me time on my commute.

    But even without a perfect system… my e-bike is still almost as fast overall as driving (at rush hour). For significant distances, I’m passing a lot of cars — either on the parallel expressway, or at multi-cycle lines for lights. It would make sense to give infrastructure priority to a mode (bikes and e-bikes) that requires less space on the road.

  7. At the macro level, in 2013 NYCDOT found:

    Without Citi Bike, users would generally have taken the subway or walked, while one-quarter would use a taxi/livery or their own car: (multiple responses allowed)

    65% would have used subway for current trip if bike share did not exist

    63% would have walked

    18% would have taken the bus

    21% would have used a taxi, livery or their own car

    9% would have used their own bike

    –> More than a 20% reduction in what would’ve been car trips is a pretty big deal.

    –> So is the space freed up on transit for those who can’t/won’t bike.

    –> So far in 2015 more than 8 million trips on Citi Bike have been made. Assuming that same rate applies, that has prevented the better part of 2 million trips in some sort of automobile.

  8. Of course as you hint at, the indirect ways transit can reduce GHG can be significant in that a place with a robust, frequent transit network:

    –> negates the need for many people to also own a car.

    –> after all, a surprising number of car trips in the US are under the 1 mile threshold and are done by car simply because it’s there. Don’t have a car in the first place? You’re much more likely to just walk that 1/4 mile to the ATM. And the denser spatial fabric of the city you live in (partly enabled by robust transit) means a lot more things are within an easy walk to begin with.

    –> since transit is indubitably more space efficient, the more it replaces auto trips the more it also reduces congestion/idling in autos that otherwise would’ve occurred.

  9. I don’t quite get your reasoning. Whatever the energy cost of running the subway, the marginal cost of adding me to the train, or savings of taking me off, is hardly measurable. If enough people switch to cycling that they can reduce the number of trains they run, I can see the savings, but I doubt very much that has happened in New York. I can see that I reduce crowding by one body, but given the couple of percent ride share cyclists represent, I doubt I and other cyclists collectively have made an appreciable difference there either. Though bike ridership is up, the trains are getting more crowded, not less. And we add to crowding on the streets (though perhaps there it’s less consequential?).

    And I’m not sure what you mean when you say that a bus has the efficiency of a single occupancy Toyota Corolla. Do you mean per passenger? That a rider on a bus consumes as much fuel as a driver in a Corolla making the same trip? I find that hard to believe, though I can’t say I know. It would help if you could explain the comparison, or how you (or whoever did the calculation) arrived at that conclusion.

  10. You buried the lead in the last paragraph. A Toyota Prius is impressively fuel efficient but incredibly space inefficient.

    Looking at just operating costs will ignore most of the costs. A Toyota Prius still needs parking at both ends of it’s trip and consumes as much if not more road space as a bus carrying 120 souls (or one carrying just 30). Moving some of those Prius trips to a more space efficient vehicle allows us to not dedicate as much space to parking, allowing destinations to be closer and decreasing travel time and energy costs. Not needing as much road space also allows for more people and more economic activity without the need to build new bridges or tear down buildings for road widenings and parking lots.

    Even so, the Prius at 50 mpg is twice as fuel efficient as the US light vehicle fleet efficiency of 24 mpg. Switching to more fuel efficient cars like the Prius is undoubtedly also part of the solution.

  11. > I don’t quite get your reasoning. Whatever the energy
    > cost of running the subway, the marginal cost of
    > adding me to the train, or savings of taking me off, is
    > hardly measurable.

    You could use the same argument to claim that flying is emission-free as long as there were some empty seats on your flight. The most reasonable way to count your carbon footprint is to count a non-zero number against you when you behave in ways that would require more vehicles, on average, if more people did it — for example, when you fly an airplane or ride a peak-hour train.

    > And I’m not sure what you mean when you say that a
    > bus has the efficiency of a single occupancy Toyota
    > Corolla. Do you mean per passenger?


    > That a rider on a bus consumes as much fuel as a driver in a Corolla making the same trip?


    > It would help if you could explain the comparison,
    > or how you (or whoever did the calculation)
    > arrived at that conclusion.

    See the DOE report, along with accompanying data tables:

    > I find that hard to believe, though I can’t say I know.

    There are a few ways we can understand this intuitively:

    1. The mantra of “ride the bus to save energy” was developed in the 1970’s when our automobiles were incredibly inefficient. Today’s Corolla burns 1/3 to 1/4 as much gas a our 1970’s autos. Note that it also burns 1/2 as much gas as the typical SUV; so an SUV driver will still save significantly by riding the bus. But it would be easier for them to just buy a Corolla or Prius.

    Since the 1970’s, buses have also become LESS efficient. This is because (a) they’re less crowded, providing more people with a seat, and (b) they’re air conditioned. In general… increasing comfort of our buses has led to decreasing efficiency.

    Moral of the story is, there is not that much economy of scale here. We know how to make 4-passenger vehicles that are about as efficient as 44-passenger vehicles.

    2. For local transport, there are real problems filling up both buses and cars. Buses waste a lot of energy on the reverse run, when they’re carrying no passengers; this leads to an average load factor of just over 25%. Cars don’t have that problem, they only use energy when they’re taking people somewhere useful; however, it’s hard to fill up all 4-5 seats, leading to a load factor of just over 25%.

    [Intercity buses have a high load factor and are incredibly efficient; however, the same will be true if you fill your family car with your family.]

    Low-speed two-wheel vehicles are the easiest way to save energy intensity on commuter transportation. My E-bike uses 1/10 the energy of a Nissan Leaf. Even five of my e-bikes use only 1/2 the energy of a fully loaded Nissan Leaf. Keeping speed down is a big win for electric vehicles (due to lowered drag).

  12. So we’re talking about how bikes can reduce carbon footprint of cities… and I said that mode-switching from public transport to a bicycle is a big win.

    Bikes have the same problem as a Prius: once you get them where you’re going, they sit around all day. It’s less of a problem than storing automobiles. But qualitatively, personal bikes are like personal autos, and are quite different from public transport vehicles or bike shares (in which energy is wasted moving the vehicles around with no one on them).

  13. Here is an excellent paper done by MIT that includes the carbon cost of building the car, bus bike. Just skip to page 10 to see the graph

    Empty buses are the worst, but a full bus is just a little worst then biking. I ride an E-bike and sold our family second car, saving loads of money on insurance, gas, and depreciation. I also get a spin class outside 5 days a week without paying gym fees

  14. If the city is dense enough, a good chunk of people will take up folding bikes. I got a Brompton and haven’t looked back – in parts of London it’s not rare to see them accepted at coat checks.

  15. Planes are much more divisible than trains, and with buses it’s an open question. If there’s not sufficient demand for a particular flight, you can be sure the airline won’t run it. If there’s no more than a few people riding a bus, the transit system might cut it in the long run, but because transit also serves as lifeline transportation, it’s not nearly as easy a decision.

  16. Because people shift from bus to bike, opening up space on the bus for either people shifting from car to bus, or people just adding more travel into their life who otherwise felt stuck at home.

  17. When bike riders heavily exert themselves they breathe out about three times as much CO2 as car drivers do when they are driving their cars. Now I will admit that the average car emits more CO2 than the average bike rider does but we must subtract the bike rider’s extra CO2 from the equation too.

    How much CO2 is emitted between farming, processing, shipping to wholesale storage, and then to retail sale? A whole lot more than the CO2 emitted driving, biking, or walking to and from the grocery store, approximately 12% of all CO2 emitted in-fact. So who here thinks that we can achieve sustainability if we don’t as much as possible localize our food supply within cities to greatly reduce the involved food industry CO2 today?

  18. You’ve misunderstood the numbers.

    The essential efficiency of MASS transportation is in carrying a *lot* of people. So a half-empty bus or train is not very efficient, but a full one is *extremely* efficient — a LOT more efficient than a Toyota Corolla.

  19. You misread the numbers. A bus is far, far, far, far, far more efficient per passenger even than a Toyota Prius…

    …IF IT’S FULL.

    The DOE numbers are based on the average occupancy across the country. They’re averaging in a lot of nearly-empty buses.

    MASS transportation should be operated specifically when it can transport a MASS.

    In New York City, most of the subway lines have all-day, both-way demand, and all the crosstown buses do.

  20. The avenues in Manhattan certainly have more than enough lanes to do that, and it should be done immediately. I’m not sure about the parkways and boulevards and expressways, which might not be suitable for bikes in some places (steep grades, sharp curves, weird merge/separate structures).

  21. 100% seat utilization is a transit pipe dream that simply cannot be achieved. If you’re going to compare thing that way, you need to compare to a Toyota Corolla full of 5 people — which is almost 5x more efficient than single-occupant Corolla.

    There are fundamental structural reasons why it’s hard to get a high seat utilization on transit, even if every bus arrives downtown packed to the gills.

    > In New York City, most of the subway lines have
    > all-day, both-way demand, and all the crosstown
    > buses do

    There is plenty of demand and economy of scale. And yet, the NYC subway is barely more energy-efficient than a single-occupant Prius. Other transit systems, including NYC buses, are even less efficient.

  22. Planes are long-distance travel, which is different from local transportation. Airlines don’t just arbitrarily cancel flights, since that would anger customers. However, they HAVE figured out how to fill almost every seat. Long-distance buses and trains can do the same thing — and do, to a certain extent. Long-distances buses are the most efficient mode of motorized transportation we have, getting 150 passenger mpg in practice. They are so efficient because of the high seat utilization.

  23. But they are also a small part of the overall system. If you have one bus line that comes every 10 minutes 18 hr/day, and one than comes once an hour from 9-5 — the inefficiency of the coverage route will have little effect on your overall efficiency.

    The REAL reason transit systems are inefficient is because they dead-head reverse trips without any passengers. And because they must travel part of their route with low utilization, as they pick up passengers. Neither of these problems is easily solved, or even undesirable. For example, the alternative to dead-heading is to build a lot of parking downtown.

  24. It’s undesirable too. You want extra seats and you want passengers to circulate comfortably and quickly. (The exceptions to that are chartered vehicles, airplanes, and long-distance buses.)

    The NYC subway is much more efficient than a single-occupant Prius, especially when you consider every single Prius trip adds to the total amount of transportation energy consumed while every additional transit passenger reduces it. In comparable traffic conditions, a bus is probably also more efficient.

  25. Well, on a per-passenger mile a Prius isn’t that efficient. The MPG rating is high, but it’s also the most optimistic rating possible.

    That is a rather misdirected concern though. Transit-oriented development is obviously much more efficient than car-centric development, and structures are wayyyyyy bigger concerns than transportation in the scheme of things.

    It’s car-centric planning that should be avoided, more than cars themselves, and driving a Prius does nothing to fix that.

  26. Sure, people exhale more CO2 during physical exertion. However, most of that CO2 is already part of the carbon cycle, since it was mainly taken from consumed plants & animals. CO2 from burning fossil fuels, in contrast, was exhumed from previously sequestered stores of carbon.

  27. Whether you breathe fast or slow, deep breaths or shallow breaths, you are just returning to the air the same CO2 that was there to begin with–not releasing any stored carbon.

  28. Barb: It’s complicated, because breathing is a byproduct of metabolizing food. Mark is correct that in the West, at least, we use fossil fuels–not to mention petroleum-based fertilizers–at every step of food production & distribution. So, replacing car miles with bicycle miles definitely reduces CO2 emissions, but doesn’t eliminate them.

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