In Praise of the Lowly Bus

Intercity buses are one of the greenest ways to travel

green busSustainable transportation geeks give trains lots of love, but tend to overlook buses.  That’s a mistake:  buses are surprisingly green.  This report, for example, finds that buses are pretty much the most fuel efficient way to travel between cities—better, on average, than rail, cars, or airplanes.

Of course, you can’t just trust one report—especially one that was funded by the American Bus Association.  But plenty of other people have found the exact same thing.  Our research on greenhouse gas emissions per mile of travel found that inter-city buses have the lowest climate impact of any form of travel.  The authors of the Consumer’s Guide to Effective Environmental Choices—which is a bit out of date now, but still excellent—found the same thing.  So did the Environmental Defense Fund. I could go on; but the bottom line is that people who care about sustainable transportation find that intercity buses are a pretty good deal for the climate.

There are two key reasons why intercity buses are so fuel efficient.  First, the average intercity bus in the US carries about 21 passengers at a time (calculated form tables 1-32 and 1-37 of the Bureau of Transportation Statistics National Transportation Statistics report.)  Second, they get between 6 and 7 miles per gallon (figure of ~6mpg from table VM-1 of the Federal Highway Administration’s Highway Statistics Series, and 6.7 mpg from WRI’s GHG protocol.)  Put those two numbers together, and you find that a bus gets well over 120 passenger-miles per gallon of fuel.  Not bad—that’s nearly as good as a Prius carrying a driver and 2 passengers! 

So it’s probably a good thing that the intercity bus industry was reporting a record increase in travel in 2008.  And if higher ridership meant more passengers per vehicle, then buses probably got even more fuel efficient than the numbers I ran would suggest. 

Obviously, bus travel isn’t for everyone.  But I’ve found that the service between Seattle and Vancouver is about as fast, and at least as reliable, as the train.  All of which suggests that buses deserve far more attention than we give them.

Update:  Some of the figures in this post were updated from an earlier version, thanks to the attentive eyes of Matt Leber.

Double update: I looked more closely at the guts of WRI’s GHG protocol—and they actually estimate that intercity buses get 9 mpg.  The 6.7 mpg figure is for the average bus, which includes transit buses (which get poor mileage because of stop-and-start driving) and intercity buses (which do considerably better).  That brings the passenger-mpg for a bus up above 180 passenger miles per gallon—about what you get from a Prius with 4 occupants.

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  1. Corey Burger says:

    Buses are a much worse way to travel than a train. You cannot get up and move around, you travel on the major highways, which are nowhere near as scenic as the Vancouver to Seattle rail line, and you get herded out of the bus for customs, unlike the train, where they come to you. The ride is also noiser and rougher.

  2. Clark Williams-Derry says:

    Sometimes, and certainly for some people. If you’re restless or a claustrophobe, a bus trip can be a pain. But I’ve rather enjoyed bus travel between Seattle and BC. At night the scenery didn’t matter much to me; I had 2 seats to myself; the customs stop was quick, and gave me a chance to walk around a bit. And it was actually faster than the train.Also, in the NW corridor, I’ve had some terrible, terrible luck with trains—2+ hours late, inconveniencing my hosts, etc. (It doesn’t help that the line between Seattle and Portland gives freight priority.) Anyway, I think it’s fairer to say “not everybody likes the bus” than “the train is inherently a more enjoyable trip than the bus.”

  3. foo says:

    Why is a bus more efficient than a train? Is it because the load factor is better? Or are trains less fuel-efficient than buses?

  4. Matt Leber says:

    I don’t understand where you found the 7.3mpg figure for buses. That table shows 6.1 or 5.9mpg for busses, depending on the year you are looking at.I would be careful when comparing the “train” to buses. Amtrak’s long distance trains are going to be very inefficient since they have amenities like large reclining seats, showers, dining cars, and observation cars. (But what a way to travel! 😉 I’d like to see a comparison of the fuel consumption of the Amtrak Cascades to Grayhound buses. This would be a better comparison since the Cascades are faster, generally more reliable, and have far fewer amenities to add weight and burn fuel. Don’t forget about the possibility of rail electrification. If you get enough rail traffic concentrated on a particular corridor or diesel prices rise for a sustained period of time, at some point electrification becomes feasible. Electricity is a far greener and less expensive energy source than diesel, no matter how it’s generated.

  5. Milan says:

    These are useful numbers.Rather than argue about bus versus train, it seems more productive to work to discourage short-haul air travel. An embarassing number of people fly between Ottawa and Toronto, for instance, despite it being a pleasant four-hour train ride (or a much less pleasant 5.5 hour bus ride).

  6. Clark Williams-Derry says:

    Matt – You’re right!! Dangit—I got the mpg for buses dead wrong. I’ve fixed it in the main post. Thanks for the catch—you’re very attentive!!


    The problem in the US is that trains are diesel powered and deadly slow whereas in Europe all trains are powered by electricity and fast. Interconnection of european train networks is done except with British Railways. In the case of France, the TGV ( high speed trains) has taken tens of millions of drivers off the road because it is cheaper and faster. But the investment is so high you need to have millions of travellers. But once the TGV rolls, nobody thinks of the car anymore as you ride at 260 km/h.

  8. Scott says:

    I’d be more inclined to ride the bus if they didn’t stop in every podunk town from here to yon. The trip from Seattle to San Francisco, for example, could be about a 14-hour trip if they’d do an express and stop only in three or four major cities along the way, but instead it’s over 22 hours. I can’t sleep worth a darn sitting up, so I’ll take an overnight bus trip only when it has become the last mode of motorized transit between here and there. (The train is fine if you get a sleeping compartment, but it’s expensive, and it, too, is slow: the train trip between Seattle and SF averages less than 40 mph.)

  9. WT de Vries says:

    And the bus’ energy efficiency can be improved even more! Just look at , under city transport.

  10. Edvaard Wu says:

    Passenger miles should include the energy cost of building and maintaining the road.I wonder what the transport costs would be then?

  11. Clark Williams-Derry says:

    Edvaard -I suppose it depends on how you do the accounting—e.g., whether you attribute the full repair and maintenance cost of the road to the bus, or only the proportionate share of the wear and tear that comes from the bus.If it’s the latter, it’s likely to be minimal. That’s what we found in our highway widening research—the GHG impacts of cars on the road quickly overwhelm the GHG impacts of the road itself, considering both construction equipment and materials. (This probably varies with the type of road, though.)I suppose you’d have to do the same for the railroad itself for a fair comparison; but I imagine that the impacts of a rail line are less significant. (That’s not an informed opinion, just a guess.)

  12. David says:

    The intercity bus is often overlooked as a travel option. My wife, a non-driver, used intercity buses frequently in the past and found the service relatively reliable, but not particularly enjoyable. 12 hours of sitting takes its toll on the body. She often travelled to smaller towns and the bus was truly her only option. It’s unlikely that I’ll live to see European style rail networks serving small communities in Canada or the US, but we need to get started getting high speed service in the highest density corridors.Seattle to SF shouldn’t take all day and make flying look like the better choice.Seattle to Vancouver has a number of other things getting in the way like the Canadian government demanding extra fees for customs clearance, but the fundamental problem with that route is the route itself. Far too much of the right of way is low-speed thanks to lack of investment, poor routing, level crossings and ancient infrastructure like the more than 100 year old Fraser River Bridge with its single track, tight corners on the north end and 8 mph speed limit. Anywhere in Europe or Asia travel between two such closely spaced cities would take less than 2 hours, not the 4.5 the Cascades needs.

  13. John Peterson says:

    It’s weird the way most urban planners and government types are hyping light rail and streetcars these days when they, of all people, should know there are less expensive and more flexible options out there for mass transit. Buses, electric trolley buses, articulated buses, buses on bus only routes are all option that seem to have fallen out of favor with decision makers. What’s up with that?

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