Is a Near-Empty Train Worse than Driving?

Acela Express #2004

Image by cliff1066 via Flickr

Riding between New York and Boston last week on a comfortable and uncrowded Amtrak Acela train it dawned on me that my comfort came at a price. An uncrowded train meant Amtrak was not earning as much revenue as it might have from this run. Beyond that, I wondered, what of the environmental impact of my trip? Everyone knows that public transportation is greener than the private alternative. But what about a sparsely populated train? They are enormously heavy machines that consume most of their energy just moving themselves, before any passengers are added. When is a near-empty train worse for the environment than driving?
Transit Occupancy Sensitivity
Just in time, James Kanter of the New York Times blog Green Inc. wrote about a recent academic study out of the University of California, Berkley that compares the environmental footprint of public transit, air travel and private car travel.

The focus of the article is on the need to take a full life-cycle approach when comparing the costs and benefits of those modes of travel. You have to consider not just the energy it takes to move a passenger one kilometer (the standard measure used for comparison). You also need to look at the energy and environmental impact of building the vehicles and the support infrastructure (including airports, runways, train stations and tracks).

The study found that “total life-cycle energy inputs and greenhouse gas emissions contribute an additional 63% for onroad, 155% for rail, and 31% for air systems over vehicle tailpipe operation.” In a nut shell, there is a steep environmental cost incurred even before any travel occurs, especially for rail and air travel.

The implication of this, according to the study is that, while improving the energy efficiency of transport is important, for modes like rail and air its also especially important to explore ways of reducing the environmental impact of the non-operational components such as infrastructure construction.

It also means that improving the occupancy rate of trains and airplanes has a greater impact on the economics and environmental footprint than it does in car travel. Indeed, the study showed that while at average occupancy rates,

train travel is always more environmentally benign, a sparsely populated train can actually use more energy and emit more greenhouse gases per passenger-kilometer than full automobile.

To me the policy implications are clear: beyond supporting research in more energy efficient public and air transit infrastructure, continue to support the use of existing public transit systems, a large portion of whose environmental costs are already sunk.

Do you agree? What are your thoughts?

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7 Comments

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7 responses to “Is a Near-Empty Train Worse than Driving?

  1. One point you missed is the behavioral aspect.

    A sparse train does more than move the passengers from point A to point B. It fulfills an implicit contract, an expectation, a “Service Level Agreement”, if you will. Without the confidence that the train schedule will meet their needs, they’ll take the car every time, not just when their schedule happens to fall in under-utilized period.

    Transit agencies make this mistake all the time — they cut service because of low ridership, which in turn drives ridership down further. And then people come along and say “See, public transit doesn’t work.”

    Also, there are environmental costs besides tailpipe emissions. The environmental cost of the HUGE amount of area paved over for cars is staggering. It contributes to water pollution, to childhood accidental deaths, and decreases the livability of our cities.

    There are only two connections between the east side and west side of my town. The cars have a total of six full-width lanes to travel between the two sides. The more usefully-placed of the two connections offers pedestrians a narrow walkway next to traffic and subject to polluted air from freeway below and traffic adjacent. This walkway is narrow enough that two pedestrians cannot comfortably walk side-by-side, and pass with difficulty. Any sort of wheeled pedestrian traffic — for example, wheelchairs or baby carriages involve someone stepping into the street. And yes, occasionally you have two wheelchairs meet — and someone has to go back downhill and start over.

    Bicycles have their own narrow lanes — but cars cross those lanes at multiple points to enter and exit the freeway, making them rather hazardous.

    This is just ONE example out of MANY around here. Caltrans recently rebuilt another bridge, adding car lanes, redoing the walkways — but not widening them.

    Unfortunately, these environmental/infrastructure costs need to be considered as sunk costs for automobiles, in the short run.

    But the thing about sunk costs is — they are sunk costs. Canceling a lightly-used train does not recoup a penny of those costs. Putting a rail passenger back into a car does not recoup a penny. There is no present action that affects costs already sunk.

    However, these costs need to be considered, in a forward-looking manner (including projected energy costs, technology improvements, etc.) when making future infrastructure plans.

  2. David Schatsky

    Great points, Bob.

    The service level agreement (SLA) concept has come up in discussions I’ve had about New York City public transportation. It’s good, but if you can’t be sure when you will arrive, you might opt for a taxi. Easily available real-time information about the whereabouts of buses and trains would help some travelers make better choices about when to set out on a journey, whether they can utilize public transit, and quite possibly boost the ridership at certain times, improving the economics and the ecologics as well.

    Thanks for writing.

  3. Ran

    A full train cannot from BOS to NYP cannot operate at all unless it travels first from NYP to BOS. Given the realities of rush-hour and personal convenience, there will always be peaks and valleys in any services yield curves. The SLA argument correctly notes that simply operating at the peaks will drive away much of that traffic. An empty Acela to New York may have previously been a full Acela to Boston. One needs to average these out when computing the environmental costs.

  4. David Schatsky

    Very true. Thanks.

  5. Pingback: Buffett Buys Burlington Northern: The Green Dimension «

  6. I’ve spent over ten years trying to pass the message that empty coal trains is wrong. When the landfill trash could be lauled back to that big hole in Wy. ,where there is no underground water to seep into.And the poploation is only two people per square mile. THis also will store this trash for future genarations to mine as a resorce.

  7. What is a train? Let’s think of it as a large car that has limitations and advantages.

    How does the traincar compare?

    1) Autopiloted (essentially to the passenger).
    2) Not available on demand.
    3) Must travel to get to use it
    4) No insurance or cost of ownership (unless built into fare price)
    5) (Can be) fast (though most US are not)
    6) Don’t have to park (although a train station and train yard is often the size of a large parking garage).

    So, suppose that in the near future cars could have some the advantages of trains. To me, the only advantages of the train car are

    1) Autopilot
    2) (Potential) speed

    So if we develop an autopilot car (or one that could be rail guided on Interstates) that can run at higher speeds (say 155 mph like the Metroliner), then there would be no advantages to trains, in fact, because cars are “on demand” trains would lose.

    Obviously we can make a 155 mph car (Indie 500). And my reading of the science is that guided autos or full autopilot using GPS, etc, is due in the next 10 years.

    Therefore, trains will shortly lose all advantages.

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