No, Cars Are NOT Greener than Buses (Even Almost-Empty Ones)

Michael Lewyn's picture

The eminent journalist Stephen Dubner recently suggested that because many buses are under-utilized, the average bus is actually less fuel-efficient than the average car.   His argument seems to be as follows: the typical bus burns more energy than the typical car- so much so that a bus with only ten passengers actually uses more energy per passenger than the average car.  Thus, an underutilized bus is less fuel-efficient than a car.

But to the extent this argument is an argument for anti-transit policies, it may be a self-fulfilling prophecy.  Here's why: suppose that a city, in reliance on this argument, adopts the panopoly of anti-transit policies common in the late 20th century- reducing transit service, building highways to places that don't have transit service, using low-density zoning to reduce the number of residences accessible by transit, etc.   By making transit less attractive, these policies reduce bus* ridership.  And the fewer riders a bus has, the less fuel-efficient it is, since a bus uses roughly the same amount of energy whether it has five riders or fifty.

Furthermore, even the mostly-empty bus has an indirect positive effect on fuel efficiency that a pure car/bus comparison doesn't catch.  Often, transit riders aren't just transit riders; they are pedestrians as well.  Unless my bus stops directly in front of my home and goes directly to my job, I am adding a zero-emissions walking trip to my commute- a trip over land that I would otherwise access by car.  And if I walk to lunch or to other errands during the workday, I am adding other zero-emissions trips to my day- trips that, if I drove to work, might also be by car.  Thus, a proper comparison is not just between an underused bus and a car, but between (underused bus + environmental impact of walking trips taken by bus riders) and the car.   I admit, however, that I do not know whether the impact of these walking trips is significant enough to close the efficiency gap between underutilized buses and cars.

And where transit is significant enough to allow people to forego cars entirely, buses create an even more positive impact.  For example, when I lived in Buffalo and Cleveland between 1996 and 1999, the transit system was just good enough to enable me to avoid owning a car.  In addition to riding (often underutilized) buses and trains, I was also walking much more than I would have done had I owned a car, thus improving fuel efficiency much more than if I had only used buses and cars.   By contrast, had these cities had a weaker transit system, I would have owned a car and used it to supplement not only transit trips, but also some of my walking trips. 

The example of Buffalo suggests that, even in cities without world-class transit systems, transit can reduce car ownership to some extent.   Buffalo has buses running until around 1 am (though often not very frequently at such hours) and a one-line light rail system extending to the city limits.  By contrast, Jackson, Ms., has buses running until 7:45 pm and no trains.  Even though Jackson is slightly poorer ** (and thus might be expected to have more people who cannot afford cars), only 11 percent of Jackson households make do without a car, as opposed to 31 percent of Buffalo households.  The example of Buffalo shows that even a mediocre public transit system can affect car ownership, and thus reduce pollution.

*Or, for that matter, rail.  However, Dubner suggests that rail is actually more fuel-efficient than buses, so in this post I focus on buses.

**Jackson's per capita income is just over $18,000, while Buffalo's is just over $20,000. 

Michael Lewyn is an assistant professor at Touro Law Center in Long Island.



mass transit efficiency

Don't overlook the fact that busses, on the average, can eliminate up to 50 vehicles from the road making traffic congestion that much less per bus. Plus the fact that often our riders (I'm a bus driver) are often people who cannot afford to operate a car or cannot drive a car due to health or age or both. Those bus routes that transport fewer than 10 people per trip I'd like to put them on my route as I drive a route where rush hour never stops. I carry standing loads all day long and, as such, can never arrive at the transit interchange on time. Yes, my route needs to either be broken into two separate routes or it needs more frequent service. It's up to the local council to decide which way it wants to go.

Cherry Picking

If looking simply at the example of the bus with average fuel economy riding along the same road as a car with average fuel economy, both with one person in each (two for the bus including driver), of course the car will use less energy. But as with any argument to support the obviously inefficient car-centric model of development, the statistics may as well have been picked by a cherry farmer.

Looking at the bigger picture, who would argue that cars are better suited than public transport for moving large numbers of people in urban environments when looking at the triple bottom line? I think even Wendell Cox would agree with this basic premise. The issue with achieving this is primarily due to the lack of cohesion between land use planning and transport systems, as most planners would understand.

In summary, yes, buses in some instances are more carbon-intensive than cars. However, as the article touches on, where does this argument get us? I think it demonstrates a need to either reevaluate under-utilised bus routes or capitalize and locate more development along them. What this argument doesn't do is justify reducing public transport provision.

Here's a handy tool for estimating transportation emissions -

Brian Labadie

cars vs. buses

I recently heard on NPR Dubner's thoughts about cars vs. buses and my heart sank. He might be right in some situations, but we know buses or light rail must be an alternative in many other places. Our roads are jammed, if only for that reason.

What I don't understand is why we don't use large buses for much used routes, and little mini-buses for making connector routes. A mix of public transportation seems to work best..

In some cities small minibuses have designated routes but are privately owned. They scurry around in Mexico City and other Latin American cities, displaying destinations for the many routes they drive to.. Sofia, Bulgaria, where car ownership is low because of cost,sees people get around using streetcars, buses, minibuses and taxis. Taxis themselves seem rather efficient as they are transporting people continually and even finding sharing passengers, and they are not taking up parking spaces. A problem Michael didn't mention when making his argument is the need for huge parking areas in cities...ugly and sometimes dangerous and certainly costly. Better that they be parks.

Here in LA we are finally rebuilding a rail system destroyed in the 1950s, partially a result of pressure from Detroit at the time. We are getting buses...almost all big but energy efficient, but they still go unused by the middle class as the routes often deliver riders far from their destination. Little mini-buses or an electric powered taxi fleet working on call would be great. .

Professional Contrarian

Dubner is a professional contrarian.

He worked on one good book, Freakonomics. Steven Levitt is an interesting economist with unconventional ideas, and Dubner got the idea of packaging Levitt's ideas in this attention-grabbing contrarian format. The result was a book with lots of intriguing ideas, which Levitt had developed throughout his career.

But Freakonomics pretty much exhausted Levitt's stock of ideas. In the follow-up book, Super Freaknonomics, they they were obviously looking hard for new contrarian ideas that could attract attention, and they came up with lots of bizarre ideas, including an approach to global warming that was widely debunked.

Dubner is obviously continuing to look hard for contrarian ideas. They seem to be getting more and more far-fetched.

The big picture, please?

While it's right to point out the human transport element, the thing completely missing from this (I heard the summary on Marketplace but didn't read the article) is that we're still thinking in the micro.

Michael alludes to the macro in his piece, but in reality, this type of development increases the carbon footprint of a region. And that's what we should be focusing on.

Transit encourages denser development, affordability, blahblahblah. But it's not really blahblah, as the Streetsblog piece points out. Because, when you look at a metropolitan area as a system, the combination of transit and dense land use is what reduces carbon footprint and they feed off each other. That's why NYC's system does reduce carbon footprint and my city (Pittsburgh), it doesn't. Let's also not forget that there's no mention of the massive increase of congestion if transit goes away. There's nothing in the Marketplace segment that even mentions that, and I doubt that development patterns will change fast enough to offset that congestion spike (240,000 more cars, daily on Pittsburgh roads alone).

This gets to why I'm posting: we need to look at the entire system, even from an environmental standpoint. We should be approaching transit from the land use perspective, and vice versa. We should be approaching both from the jobs access perspective, the quality of life perspective, and economic vitality. It's through those three that you make your argument, not on environmentalism alone. Trust me, as a professional advocate, you'll lose that one every time. Get to the environment through the economy, not the other way around.

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