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Average and Marginal Environmental Cost (Wolff)

Jonathan Wolff

How bad for the environment are different forms of transport? It is common to assume that air and road travel are much worse than rail. Maybe this is right, but how exactly is it to be calculated? There are many types of environmental impact, and it is not obvious how they should all be taken into account.

Suppose we start with the simplest calculation, and imagine that I have the choice either of staying at home or taking a trip by air, rail or road. Assuming that the train or plane will depart whether or not I am on it, the only cost of my travelling will be the additional fuel needed to carry one person’s body weight (assuming too that the seat would have been empty had I not been occupying it). Calculated this way presumably flying and going by train come out well; driving very badly.

However this line of reasoning looks very superficial. Average, rather than marginal, fuel costs will be very different, and more information is needed – more than I have at present – to calculate average fuel use per passenger per mile, per hour, or per typical journey, for the different modes of transport. But I assume that it is this calculation which is behind the common argument that air travel is, comparatively, so damaging.

Fuel consumption, and the consequent pollution and effects on the climate, are obviously vital considerations. But there are other issues too, such as the cost in terms of resources and energy in manufacturing the plane, car or train, and then of maintaining it. Furthermore, the infrastructure to make such travel possible needs also to be taken into account. Airports, of course, have a huge environmental impact. But planes have the advantage of not needing roads or tracks, both of which are very expensive to produce and maintain. As well as its obvious environmental impact, a road needs ballast, concrete, tarmac and so on, while railways need enormous quantities of steel, timber and gravel, which have to be renewed at intervals.

I’m too lazy to look into relevant research on this, but surely someone must have done? My question is whether there is any research suggesting how to compare different forms of environmental impact, and calculate the comparative average cost of train, air and road travel, mile for mile. Next time I need to travel from London to Scotland what should I do? (I know, I know, I should stay at home in an unheated darkened room …)

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7 responses to “Average and Marginal Environmental Cost (Wolff)”

  1. Patrick S. O'Donnell

    I can't answer your question (and, perhaps thankfully, what little travelling I do for work and our close proximity to school and town, allows me to ride my bicycle more often than not, weather permitting) but a nice introduction to the subject of 'ecological economics' in general (a propaedeutic to your question?) remains Partha Dasgupta's Human Well-Being and the Natural Environment (New York: Oxford University Press, 2001).

    Reply
  2. Eric B.

    What I find missing from your calculations, Jonathan, is a consideration of the unavoidable voting-with-your-feet influence you exert any time you utilize any form of transportation. When you buy a plane ticket, you put plane tickets, in general, in higher demand. this in turn encourages the airline to expect more demand for tickets, and so eventually to increase the number of flights to your destination. Of course your one ticket alone doesn't do this, but one must consider the web of consumerism s/he is stuck in.

    Likewise, every time you use your car you are putting more wear and tear on it, so that you will have to buy a new car that much sooner. If we assume (unwarrrantedly) that a car has a set number of trips in it, then the more frequently one takes those trips, the more cars s/he will end up consuming in a life time. And the more cars we consume per life time, the more we encourage Detroit, Munich, and Tokyo to crank out more cars to meet that demand. But do all these consumptions cancel each other out? If every time you fly you discourage the auto industry, and every time you drive you discourage the airline industry, then maybe it all comes out in the wash.

    Also, it must have something to do not with actual but with potential energy expenditure. So a car can potentially fits five passengers, whereas a plane can potentially fit 200, and if you are one person on a flight that's half full, then that's only 50% wasted energy, whereas if you drive a car alone, that's 4/5, or 80% wasted energy.

    Well, just some thoughts. I think about these things too but I consider myself an a priori environmental ethicist. Who needs "data" on fuel efficiency, etc.?

    Just kidding…a little.

    Reply
  3. Iain

    I seem to recall reading somewhere – possibly an in-flight magazine, admittedly – that flying is much more fuel efficient in terms of consumption per passenger mile than driving. This looks fair enough: planes're big. But the matter is complicated when we take into account things like the altitude at which an aeroplane reaches this efficiency. The emissions at high altitude have, I believe, a disproporionately damaging effect on the environment. (Don't know why: I'm rubbish at science…) Additionally, according to New Scientist a few weeks ago, flying at night is worse than flying during the day.
    Don't know how that'd bugger up your calculations… but I'm sure that it would!

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  4. Albert Atkin

    I don’t know if this is quite what you have in mind, and I can’t vouch for it’s authority – it was compiled by Northwest Environment Watch and calculated using data compiled at the U.S Department of Energy – but these statistics are average carbon emissions per passenger per mile.

    CO2 Emissions in lbs per passenger per mile.

    SUV (1 driver fuel consumption of 15mpg)= 1.57
    Average Car (1 driver fuel consumption of 21.5mpg)= 1.10
    Jet Travel (Average capacity) = 0.97
    Mass Transit (1/4 full) = 0.75
    Economy Car (1 driver fuel consumption of 40 mpg) = 0.59
    Intercity Trains (average capacity) = 0.45
    Carpool (3 people in an average car) = 0.37
    Mass Transit (3/4 full) = 0.26

    My guess, though, is that these kind of statistics will never capture or take account of all the factors that effect the environment. For instance, recall all frenzy about contrails after the post 9/11 three day enforced grounding. The vapour trails left by airplanes appear to contribute to temperature variations for reasons beyond CO2 emissions.

    Similarly, roads contribute to increased flooding. To quote from the U.K. Environmental Agency’s advice on flooding, “Drainage systems and hard surfaces, such as roads and car parks, can also increase flooding by quickly transferring rainwater into rivers”. There are many other factors, like the effect of noise pollution on animals breeding and nesting habits.

    National Rail in the U.K apparently sources its wooden sleepers from sustainable forests. Presumably travelling on tracks maintained by national rail has less environmental impact than travelling on lines that don’t source sustainable materials. Plus, we seldom use one type of transport to complete a journey, and we might have to consider how independent of other modes of transport a given mode is in calculating it environmental impact. Whilst, “planes have the advantage of not needing roads or tracks, both of which are very expensive to produce and maintain” airports are built away from large residential centres and are not that easy to access except by road or rail. The millions of fliers, workers, freight and so on that pass through airports everyday have to travel to and from the site by road and track.

    I suppose we can hope that trying to get a grip on all the factors will lead to 'paralysis through analysis' and no-one will travel anywhere.

    Reply
  5. Bruno Verbeek

    Some time ago I filled in the on-line "ecological footprint". In it, I was asked about my typical way of travelling. This suggests to me that there exist established and accepted ways of calculating how much it costs to move you from London to Edinburgh by car, train, airplane, (or bicycle).

    If I had to put money to it, I'd guess that train comes out the least costly (excluding cycling up there…) for the environment, but I am too lazy to check it out.

    See also http://www.myfootprint.org/
    http://www.mec.ca/Apps/ecoCalc/ecoCalc.jsp
    http://www.germanwatch.org/klak/flug04e.pdf#search=%22ecological%20costs%20of%20flying%22

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  6. Lloyd Reisman

    Interestingly, there was a program on PBS/WLIW recently that discussed the beneficial effects of clouds produced by airplanes. Those clouds actually have an insulating effect on global warming and help keep our temperature lower than it would be without them.

    The study was made possible largely because of 9/11 when air traffic was suspended for a number of days following the terrorist attacks. This allowed some of the airplane clouds to dissipate and readings were taken about changes in temperature. The results, to some scientists, were remarkable enough to suggest that the clouds produced by airplanes have actually helped slow the warming process.

    So, in that sense, out of the choices of air, rail or car….air actually has some positive side effect on the situation, while the other 2 appear to only have negative consequences.

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  7. Lloyd Reisman

    Disregard my previous post, I misinterpreted the results of airplane contrails, as they are called, and their effects are still inconclusive. You can find out about them on the PBS NOVA page if you care to look.

    Reply

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