High-Speed Rail and CO2


One of the less-publicized components of the stimulus package was an $8 billion commitment to develop a high-speed rail (HSR) network in America. This is no more than a down payment, given the very large sums needed to build HSR (University of Minnesota transportation scholar David Levinson estimates that the proposed California segment alone will cost $80 billion, or more than $2,000 per Californian; given my state’s financial problems, this is going to require a very large bake sale).

Since this policy appears to be a personal favorite of the president and other officials, the needed funding may well materialize down the road. But it is worth asking whether the touted benefits will too.

Backers cite many gains to be reaped from HSR, including relieving crowding at airports and on highways; cutting the need for expensive new air and road infrastructure; preventing road fatalities; reducing travel times and costs; promoting economic development (particularly in areas not well covered by air service); improving travel reliability; boosting productivity; spurring technological advances; stimulating the economy/creating jobs; and, because HSR will run on electricity and may require less energy to move each passenger, reducing greenhouse gas emissions.

This is a long list and the blog is a short medium. So for now let’s just consider the final point about HSR’s environmental benefits. Under some conditions, there is no doubt that an HSR system would reduce greenhouse emissions. Unfortunately, a study undertaken by the consulting firm Booz Allen Hamilton for the U.K. Department for Transport raises some troublesome questions about whether these conditions can be met in reality.

Booz Allen considered two potential U.K. HSR lines (London-Manchester and London-Edinburgh/Glasgow). They found that the CO2 emissions required to move HSR passenger seats were about the same as those required to move automobile seats — hardly a slam dunk for rail. In fact, intercity bus came out considerably cleaner than HSR on a per-seat-mile basis.

HSR would emit less on a per-seat mile basis than air travel. But the major caveat is that all of these figures consider emissions from operations only, without taking into account the very large amount of pollution that will be created in the construction of the HSR system.

When the emissions spewed by all those earth movers, tunnel boring machines, bulldozers, trucks, cranes, etc. are taken into account, the carbon advantage for HSR vis a vis air travel largely evaporates.

What would the bottom line be if the proposed U.K. lines were built? It all depends on how many people shift from air to rail; the more HSR passengers the better. But the authors found that even if the mode split on the proposed London/Manchester line shifted from 50-50 air/rail (approximately the current distribution) to 100 percent rail ridership, emissions over a 60-year period would be lower if the HSR line was never built.

The picture for HSR is somewhat brighter for a proposed London/Scotland line, because that corridor currently has a low 15 percent rail share (meaning there’s more scope for people to switch to rail). But to make the rail line worthwhile, HSR would have to capture almost two-thirds of the air/rail split. This is not impossible, but it may prove difficult given that air travel has a considerable speed advantage over HSR and will continue to do so in the future. (For reference, even the California HSR authority, which strongly supports the program, forecasts that rail will attract only one third of the air/rail split in the California corridor).

There are, of course, many uncertainties involved in this type of analysis. Technological advances may make electricity production cleaner in the future (though airplanes’ fuel economy may improve as well). Obviously Britain is not the U.S. (although given its high population density and short distances, Britain may actually be a better place for HSR than most areas of our country).

Still, the results of this study deserve careful consideration. No one argues that futuristic rail isn’t a great way to get from Main Street U.S.A. to Epcot Center (usually). But given the very severe budget constraints we are currently facing, a program as costly as HSR should be evaluated very thoroughly despite its considerable allure.

Hat tip: David Bayliss

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  1. Marcus says:

    I applaud the attempt to examine a “green” policy and see whether or not it will actually reduce green house gas emmissions, and I largely agree with the points in this post. But I do have a (large) quibble: when evaluating the impact on emissions of HSR, you obviously need to look at the changes in how people utilize mass transit. I do not know anyone who currently uses rail lines for interestate travel outside the eastern corridor (between Boston and DC) with any regularity. If a major component of emissions impact is:
    ” how many people shift from air to rail; the more HSR passengers the better”
    then wouldn’t the US market represent a major opportunity because so few people currently use HSR? I imagine we have lots of marginal air plane passengers who would be willing to try HSR because they dislike flying or find it too expensive.
    Full disclosure: I am not an environmentalist.

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  2. Robert says:

    Yes, it is costly in environmental terms to build HSR lines. But what about the cost of building roads (or even just maintaining them)? What about building airports?

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  3. noah says:

    A distinction needs to be made between direct and indirect emissions.

    If HSR is 100% electric, then it doesn’t have to emit anything. Cars and planes do. We can’t make any investment in sustainable technology without CO2 emissions in the short term.

    100% electric technologies do not emit anything directly. They run just as well on nuclear, wind, solar, etc. as they do on coal. Once we replace the power plants, we will have a 0 emissions infrastructure in place without any additional investment or emissions.

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  4. Erik says:

    What if you include the carbon it took to build all the freeways between SF and LA?

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  5. Jonathan says:

    The start up costs for almost all forms of transit are high. This same argument could have been used for the Erie Canal and the Interstate Highway System.

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  6. Leonard says:

    It seems this study doesn’t take into effect the reduction in carbon emission attributed to lifestyle changes surrounding HSR. When a society moves toward a rail-based transportation infrastructure from a primarily road-based one, people tend to settle in denser, walkable neighborhoods with smaller home sizes. This reduces the amount of car use, overall, while smaller living spaces reduces the energy used (and, hence, the carbon footprint) to heat and cool those houses. A road-based transportation infrastructure, on the other hand, promotes sprawling, low density, segregated land uses and large houses that use more energy per capita.

    Finally, it should be noted that the California HSR was never about reducing carbon emissions, but primarily about reducing long term costs. It was estimated that building all the necessary road and runway space to accommodate the same amount of passenger growth would have far exceeded the costs of building the HSR system.

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  7. Jason says:


    I think your article over looks the fact that diversity of transportation, especially adding HSR, reduces wasteful energy use which is where most of the C02 pollution is taking place. UK studies really don’t apply here because in general the UK is not nearly as wasteful with their transportation as we are. They don’t have a I405. It doesn’t take them 2 hrs to get to work if there commute is over 30 miles.

    Your analysis, thoughtful to your title did forget two central aspects.
    1 .Growth rate of general population and travelers. Though building HSR will have some negative environmental impact , it will still reduce the overall environmental reduce impact as our population grows. It is much cheaper, efficient and less environmental impact to control C02 at central locations which is what electricity offers. Even building the HSR environmental impact can be negated with current technology and practices. The real question is what will the C02 impact be if we don’t build one?

    2. Basic theory of diversity. Your analysis missed this key aspect. By spreading the transportation love where movers take more efficient forms of transportation for their needs will have less impact with C02 emissions. The extremely positive aspect of HSR and C02 is the lack of wastefulness it has. Did the analysis factor in the C02 wasted every time a plane sits on the tarmac due to over capacity? Every time a car is stuck in traffic due to over capacity? Adding HSR will open capacity and reduce wasteful energy consumption.

    The work /C02 ratio out of construction equipment isn’t nearly as wasteful as it would be on other forms of transportation.

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  8. DaveyNC says:

    The whole “green” movement is so impossibly convoluted and complicated that it cannot possibly be implemented with any assurances that it will achieve the desired outcome. It’s an example of an affluent society trying to salve its conscience and in the process making matters worse, or at least no better.

    @2 Robert–A few questions: Do you expect that just because we build HSR we will not maintain the roads? By building an HSR project, wouldn’t we be simply adding on to existing “greenhouse gas” emissions? What about building multiple train stations that can accommodate the HSR, parking, offices, maintenance facilities, etc.?

    Outside of the largest Northeastern metro areas, ridership spikes when the cost of operating a car spikes. Otherwise, they mostly operate at a loss or break even. (At least that’s the way it was when I lived in Atlanta.) So then you have to add the societal cost of that dislocation to the cost of HSR.

    Like I said, the green movement is strictly a project of importance to affluent societies. Less affluent societies aren’t interested, as India just made crystal clear to Sec. of State Clinton.

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