Sustainable 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 The authors of the Consumer’s Guide to Effective Environmental Choices—which is a bit out of date now, but still excellent—found the same thing.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.