Can Mass Transit Save the Environment? Right Wing or Left Wing, Here’s a Post Everybody Can Hate

(Photo: RJ Schmidt)

A major rationale — perhaps the major rationale — touted by supporters of mass transit is that by reducing our output of greenhouse gases and other pollutants, transit can help save the environment. The proposition seems intuitive and even obvious: by no longer encasing each traveler in thousands of pounds of difficult-to-move metal, surely transit is more energy-efficient. Plenty of analyses prove this. But then again, Aristotle, who was revered as the infallible font of truth for more than 1,000 years, proved that heavier objects fall faster than lighter ones and that women have fewer teeth than men. Might studies that demonstrate transit is greener be similarly wrong?

They might. The reason is that many studies of energy efficiency by mode often make questionable and — depending on the author’s point of view — self-serving assumptions. The main trick is to look at autos with but one passenger and compare them to transit vehicles in which every seat is full. (For example, see this.)

But in the real world, this is emphatically not the case. At any given time, the average auto has somewhere around 1.6 passengers, and the average (typically 40-seat) bus has only about 10. Rail vehicles typically have more passengers (on average about 25), but then again they are also typically much larger. Thus their average load factor (percentage of seats filled) is also not high, at about 46 percent for heavy rail systems (think subways in major cities) and about 24 percent for light rail (think systems that mostly run at street level).

It is not clear that moving around large and largely empty vehicles is much of an improvement over moving around smaller ones. In fact, it may be worse. According to the Department of Energy’s Transportation Energy Data Book, in 2010 transporting each passenger one mile by car required 3447 BTUs of energy. Transporting each passenger a mile by bus required 4118 BTUs, surprisingly making bus transit less green by this metric. Rail transit admittedly fares better, at 2520 BTUs per passenger mile, but even this is not the kind of slam-dunk advantage over the auto that transit advocates might hope for. 

There are some qualifications here, some of which aid transit and some the car. The sources of transit’s energy—electricity in the case of rail, and often natural gas in the case of bus—are typically cleaner than those of the auto, so that even with higher energy usage, transit may produce fewer greenhouse gases. Still, even taking this into account, a bus produces more CO2 per passenger mile than the car for most trips.

Transit looks better when the environmental costs of building the vehicles and infrastructure are spread over the passenger miles that each mode will accommodate. Taking this into account, an average bus at normal load factors does currently produce slightly fewer pounds of CO2 than autos, and rail transit does much better.

On the other hand, electricity is not much cleaner than gasoline if it is derived primarily from coal, and in some states, such as—surprise—West Virginia, nearly all of it is. And in any event, the electrification of autos is advancing. Moreover, greatly increased fuel economy, even for regular old internal combustion vehicles, is rapidly making cars more efficient. By the time the new fuel economy standards for autos are reached in 2025, a new car’s average mpg will have increased from 27 to about 40, meaning that in terms of energy efficiency, cars may leave buses behind and begin to be competitive with rail. 

Does this mean that efforts to increase ridership will not help—and may even harm—the environment? Not so fast. In fact, the environmental benefits of higher transit ridership might be very great—but they depend completely on how those increases are obtained.

Pumping up ridership by adding transit service will probably do little good, and may even be counterproductive. The reason is that new service promises to reduce transit’s already less-than-spectacular load factors and result in largely empty vehicles.

Why? At this point we have picked all the low-hanging fruit in terms of transit markets. We already have extensive rail transit service in the places where land use and demographic characteristics are congruent with high transit use—such as central Chicago, Boston, the San Francisco Bay Area, Washington D.C., Philadelphia, Los Angeles, and (writ very large) New York City. For the most part, any new transit service has to go to relatively low-density cities and low-density areas within cities, meaning that new investment would drag transit’s overall efficiency down, not up. 

To give an idea of how this phenomenon works, the heavily used New York subway system (58 percent of seats are typically filled) produces .171 pounds of CO2 per passenger mile, less than 1/3 the average for cars nationwide. However, the much more lightly used Cleveland, Pittsburgh, and Memphis light rail systems actually produce considerably more CO2 per passenger mile than cars do. Unfortunately, due to diminishing returns, new rail transit systems are more likely to resemble the latter three than the former one.

On the other hand, if we can persuade travelers to leave their cars and ride existing transit service, rather than new service, the environment will benefit greatly. Given its current low load factors, transit generally has plenty of capacity to absorb new customers with practically zero additional energy expenditure.

Strategies to pursue this would involve economic incentives to influence behavior. These might include pull strategies designed to lure riders onto transit, such as fare cuts, or push strategies designed to get them out of cars onto transit, such as increasing gas taxes, congestion tolling, or charging market rates for street parking. Note that pricing strategies of this sort would also help the environment by raising auto efficiency through increased incentives for carpooling. 

Thus it makes more sense to focus on policies that attempt to change travel behavior as opposed to building infrastructure and buying vehicles. However, public policy in recent decades has self-defeatingly focused on the latter strategy, not the former. This has proven very popular, since shiny new trains and buses allow politicians to take credit for very visible improvements, while the costs of said infrastructure and equipment are essentially invisible since they are spread broadly across the American public and are hidden in arcane budgeting processes. (With a thicket of passenger fares, fuel taxes, sales taxes, bonding, advertising revenue, etc. coming from federal, state, regional, county, transit district, and municipal administrations, it can be difficult even for experts to determine who pays what for transportation.)

So there it is: to benefit the environment, probably the best thing to do is be very skeptical about adding new transit service and even to discontinue some service we are currently providing (sorry, liberals). Simultaneously, we should raise fees and taxes for driving (apologies to you conservatives). The best I can offer to keep the comments section below free of hate posts is that at the moment the chance of either happening is small. This may make good sense given the current political atmosphere—but it makes little sense for the atmosphere of the planet.

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  1. Min says:

    Hm, one thing I’m wondering is, by taking a car off the road when converting a driver to a commuter, does that reduce congestion in the roads, thus leading to an increase in gas mileage for drivers? If that’s a large enough effect, should the lowering of car pollution due to the higher MPG be credited to public transit, not to cars?

    Well-loved. Like or Dislike: Thumb up 48 Thumb down 3
    • Rex says:

      Reducing congestion also incentives more people to drive

      Well-loved. Like or Dislike: Thumb up 27 Thumb down 7
      • Michael Peters says:

        But no more than before. Capacity hasn’t changed you’ve just reduced congestion so it’s still a net win for everyone.

        Hot debate. What do you think? Thumb up 12 Thumb down 10
      • Vince says:

        @Michael Peters: You’re ignoring the pent-up demand for driving that exists in regions with high levels of auto congestion in which case a decrease in congestion increases demand for driving trips.

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    • JAM says:

      One thing I never see discussed with respect to light rail systems is the congestion they create at crossings in downtown areas. Many times it seems that when the light rail comes through, cars back up for blocks with there motors running, waiting for the crossing to open.

      Not sure how it plays into the overall numbers, but it should be counted in the analysis.

      Well-loved. Like or Dislike: Thumb up 27 Thumb down 6
      • etherist says:

        YES! This is my frustration with light rail in the medical center where I work. I can wait 3-4 minutes for a light to cycle if there are a north-bound train and a southbound train approaching the intersection where I am waiting to turn left.

        I would love to be able to take bus/train to work, but that would trade an 10 minute pleasant drive by car for a 30-40 minute unpredictable commute by bus and train, including a 5-minute walk to the bus stop and a 5-minute walk from the train stop to work.

        Thumb up 5 Thumb down 4
      • jkg says:

        Yes! And those pesky people walking too! We should get rid of them walking across the street and then MPG would really go up!

        Well-loved. Like or Dislike: Thumb up 18 Thumb down 7
      • Vince says:

        At the same time, the congestion that is created by the train decreases the demand for driving by increasing commute time. In your case, it still makes sense to drive; for other people, the additional congestion created by the train is enough to get people out of their car and into alternate modes of transportation.

        Thumb up 2 Thumb down 2
      • Jonah Gruber says:

        Another thing that is never discussed, and I’ve been reading a lot about this fairly controversial issue from many different perspectives, is the bigger picture in terms of cost:

        – Over 30,000 people are killed in the United States in car accidents every year. Many hundreds of thousands more suffer serious injury. What is the overall cost of these deaths in injuries? The cost to the health insurance pools? The burden on our strained medical system and emergency response system? How does this compare to the relative safety of rail?

        – If you talk about foreign oil dependence, you have to talk about what the REAL price of oil is. How much of our defense budget is appropriated to defending and securing petroleum sources? What is the actual impact of fracking and the infrastructural costs associated with it? This is a huge debate in and of itself.

        – What is the economic impact of having a rail-based economy versus a car based economy? When gas prices go up and people can’t get to work during a recession, are they in a worse position than those who are able to take the train or rail?

        – Here’s a weird one but an interesting one. Are people who ride public transit less stressed than rush hour drivers? According to APTA, “People who live or work in communities with high quality public
        transportation tend to drive significantly less and rely more on alternative modes (walking,
        cycling and public transit) than they would in more automobile-oriented areas. This reduces
        traffic crashes and pollution emissions, increases physical fitness and mental health, and
        provides access to medical care and healthy food.” Wow! That sounds like hundreds of billions of dollars of value right there.

        Simply comparing train size to car size is shoddy science. Railways can add more and more cars. Roads need to continue expanding into sparser areas. The above article does not go into the cost effectiveness of city density, which makes one question it entirely. Simply ending transit service based on Eric Morris’ argument would be devastating to imperiled outer urban areas where working class people live. What would the cost of paying for all of their food stamps be when they lose their jobs?

        Well-loved. Like or Dislike: Thumb up 6 Thumb down 0
  2. Laurent Duval says:

    Are averages really pertinent when discussing mass transit load ratios ? I mean, if you’re taking a subway ride at rush hour on a very busy line to commute between your home and your workplace, you won’t suddenly switch to that very quiet line over there, far from both, just because there’s an incentive to use mass transit more. Of course, adding more overloaded buses, subway cars and trams on busy lines will raise the average, but at the probable cost of more users opting out due to discomfort (or even insecurity, as it’s the case in my city, Paris).

    Well-loved. Like or Dislike: Thumb up 20 Thumb down 3
  3. Gary says:

    Here in Wales ,one gets a free bus pass at 60 years old- this is the best incentive for me to use the bus and according to your article I’m only filling an otherwise empty seat- my partner and I only need one car between us ,the car gets used less so lasts longer and congestion and CO2 are reduced. I must be in eco-heaven already -and if you get on the double decker the view from upstairs of the hills one side and the sea the other is stunning.

    Well-loved. Like or Dislike: Thumb up 35 Thumb down 4
  4. Brent says:

    The answer is autonomous cars. Distributed, flexible, & minimal infrastructure costs.

    Well-loved. Like or Dislike: Thumb up 35 Thumb down 13
  5. martin says:

    You might also consider that having a car also encourages people to travel longer distances than they typically would just riding mass transit. So even if the passenger mile efficiency is worse it could still lower emissions overall due to fewer miles traveled.

    Well-loved. Like or Dislike: Thumb up 40 Thumb down 6
    • Katherine says:

      How does having a car incentivize people to drive longer distances? I would think the opposite could be true. If you are driving somewhere, you can take the most direct route. When you have to use public transit, you might need to make a few transfers or take a line that is not as direct.

      Thumb up 5 Thumb down 4
      • Betsy says:

        I don’t think “longer distances” in this case means taking a longer route to the same destination, it just means driving more often. Personally, when I am taking the bus, I organize my errands more efficiently, whereas when I have a car and can drive from one side of town to the next twice a day on my own time if I want to, there’s less incentive to limit my trips. (Obviously I will have to still have to pay more for gas, but that is a delayed negative consequence and doesn’t affect my decisions as strongly.)

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  6. Jeff says:

    I see a lot of sides to this debate and one is on the price component, specifically those that argue it’s too expensive of a project to take on…but do the detractors pay attention to the cost of car ownership?

    Wow…$8,946 for the average sedan and $11,370 for the average SUV…ANNUALLY. Now multiply that out for the number of vehicles on the road (there are stats for that, too)…

    So let’s take the lesser figure ($8,946) and reduce the total number of cars by just 1% (2.5 million cars)…and redirect those funds. Hey, we just came up with $22.3 billion.

    Yes, it’s much more complicated than that…just pointing out the argument of “I don’t want to pay billions for my transportation” is seriously jaded as we already pay trillions annually to this for our cars. If we could convert auto manufacturing plants quickly to create tanks for the military in the 1940’s, surely we could convert empty factories (or live ones, for that matter) to create parts necessary for rail in the 2010’s, right?

    Well-loved. Like or Dislike: Thumb up 34 Thumb down 8
    • joe J says:

      The real problems with your math is. Althought 1% sounds small it is actually huge to get that many people to change their life style. Even if they took mass transit they would still have cars to go places mass doesn’t go. so reduce it to .01% change. And compare that to the cost of just Californias light rail that some are pushing which is projected to be $100 to 300 billion, for just that project alone. So even if this project stopped every single Californian (about 2% of the country) from having a car. it wouldn’t be close to cost effective

      Thumb up 9 Thumb down 6
      • Rxp says:

        You’re comparing the gains from reduced car ownership, which are annual, to the total cost of California light-rail. So, in your example, we’d break even within 5-15 years.

        Thumb up 4 Thumb down 6
      • Joe J says:

        Only if you assumethe laughable that there is zero anual cost to running the light rail. It’s annual projection is also about 5-10 bill/yr. So it would never break even.
        And that assume the part I had commented on which was this one project would not get rid of 1% of the cars in the entire US, since it could oly effect those in a part of California, so using the 1% (22 billion) value is ridiculous. An overyl optimistic view would be .01%. Which would put the potential savings on the order of .2 billion. or a net loss of several billion per year.

        Thumb up 7 Thumb down 4
      • cm25 says:

        FYI: California makes up 12% of the total US population, not 2%.

        Thumb up 4 Thumb down 2
    • etherist says:

      The cost of driving my Japanese coupe to work are about $7,000/yr considering depreciation, maintenance, fuel, insurance, and parking. I typically go to work 200 days/ year.

      But I would still own a car if I took mass transit to work! My choice.
      Mass transit to work every day would cost close to $1000/year in passes. The _excess_ cost of me driving to work (still have to pay insurance + parking , although less gas, maintenance, etc.) is probably about $2500.

      I would love to be able to take bus/train to work, but that would trade an 8-10 minute pleasant drive by car for a 30-40 minute unpredictable commute by bus and train, including a 5-minute walk to the bus stop and a 5-minute walk from the train stop to work. My commute home by car is a little longer, 15-20 minutes.

      Mass transit would add at least 45 minutes/day to my commute. Multiplied by 200 days/year = 150 extra hours/year spent on mass transit, waiting in 90+ degree heat and humidity, in the cold, in the rain.

      I can easily afford the extra $2500/year and consider it money well spent.
      My office mate, who leases an M3 ($2000/year on TIRES + $1200/month lease! etc.) lives out in the suburbs, and really has no mass transit option. His drive is probably an hour round trip. Poor slob. I chose to pay more to live in the big city, with all the hassles, to have more time at home with my kids instead of in the car.

      My office mate made a different choice, and I think he’s reconsidering it.

      Thumb up 1 Thumb down 0
  7. Rashad says:

    I’m surprised that in your final paragraphs you didn’t talk about the central factor that makes mass transit work – population density! If you can’t build high density housing near your mass transit stations, then yes it is pointless, but if you can then it clearly seems worth it.

    Well-loved. Like or Dislike: Thumb up 59 Thumb down 1
    • Steve says:

      This is clearly the point missing from the article. The suggestions in this article are all focused on HOW people get places, not WHERE they are going from and to. The biggest problem the US has in terms of transportation is the truly insane development patterns post-WWII, which got really bad by the 1980s and 90s. Only in the last 10-15 years have we started to rethink our concepts of development and start to… not exactly move toward a more sustainable kind of development, but at least move away from the truly absurd, 100% car-oriented modes of development we have used for the last 50 years.

      Well-loved. Like or Dislike: Thumb up 16 Thumb down 4
      • FrMartinFox says:

        The “problem” is that in the U.S., people are free to live where they like and go where they like, stay as long as they like, and shape their own plans. The “problem” is freedom.

        I live in Ohio, where there has been talk of building a supposedly high-speed rail link from Cincinnati to Columbus and Cleveland. It would cost a fortune to build, and not be high-speed until another chunk of money is spent. It sounds so good–until you think about this question: why would people who can drive–and have the options I mentioned above–choose the rail instead? If you take the rail, you have to leave the business trip–or the family event or baseball game–according to the rail timetable. If you’re shopping, you won’t have the trunk and back seat of your car to carry your loot. And so it goes.

        So, yes, the fact that people get to go where they want–as Steve and many planners lament–is the “problem” that makes many mass-transit plans untenable.

        Hot debate. What do you think? Thumb up 21 Thumb down 17
      • JesryPO says:

        Of course, it is a “problem” because there actually is NOT choice and freedom in most cities with regards to housing. Good luck finding a townhouse without a yard to maintain in Texas or full-service condominium near shopping and entertainment in Indiana. We don’t build them, because we do not have the infrastructure to support them, forcing those (like the educated young) who do not want to live in a single family house on a quarter acre to “choose” to live in Chicago or New York. Not to mention the abysmal “choices” we give to our mobile elderly…

        Well-loved. Like or Dislike: Thumb up 14 Thumb down 4
  8. Enter your name... says:

    I didn’t think that greenhouse gas emissions were really a big goal for promoting mass transit. After all, we started promoting mass transit even before anybody knew what a greenhouse gas was. I thought the main goal was to get more people to/from work during rush hour (in particular) without having to waste real estate and infrastructure on places to drive and to park quite so many cars.

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    • triclops says:

      In the US, especially here in CA, the CO2 argument has been used a lot recently. Basically, whatever argument the proponents think is currently the trendiest is used. It has been about the environment, creating jobs, helping traffic, and myriad other half-truths.

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      • twofortyseven says:

        Triclops, your comment implies that there’s some sort of evil agenda that proponents of public transportation have, which they mask with “trendy” arguments they don’t really believe about jobs, environments, traffic, or CO2. So what is that hidden agenda? The only people who really have hidden motives here are the contractors who build the rails and busses, which I believe would account for a small percentage of the vocal supporters of public transportation.

        For the rest of us, it’s because we actually believe the arguments in support of public transportation. These arguments might be half-truths or flat-out wrong. People can believe things that are false. But that doesn’t mean we’re just bandying trendy arguments and half-truths to mask our real motives.

        Thumb up 3 Thumb down 0