Is Mass Transit Eco-Friendly?

Nyc subway maps

As part of my regular podcast routine, I got to the Freakonomics podcast and it was on one of my favorite topics: mass transit/public transportation. I’ve always thought intuitively that mass transit/public transportation is better for the environment. I never really thought about it aside from a cost standpoint (where the DC area subway system is not cheaper than driving for my schedule).

Dubner’s article doesn’t completely buy into the benefits of mass transit, basically saying it can help the environment or it can actually harm. this other article criticizes the validity of the article, which is compelling, but I’m not sure.

this is where it is important to note that the only measure they are looking at is environmental impact as a direct cause of using mass transit or other alternates. I’ll get into why this is important later.

so the biggest factor as far as whether or not mass transit is better environmentally is ridership. the energy consumption for a subway train to move 50 people or 160 people is a small difference, making it more efficient to move more people. this means (using the 1.6 passengers per car stat) there are 100 fewer cars on the road for each subway train. after doing the math, Dubner finds the more people you can get using public transportation, the more positive environmental impact you get.

what’s surprising is that if the ridership is on average too low, then it actually is less environmentally friendly to run the public transit. the bus example is the best at showing this – Dubner has numbers that the average passengers per bus is 10 (super crowded rush hours and super not-crowded nights). this means one bus can offset 6.25 cars (10 passengers per bus/1.6 passengers per car) – but if the environmental impact of a bus is greater than the environmental impact of 6.25 cars, then it will be better for people to drive.

these numbers are particularly important for cities who are looking to expand mass transit services (like the DC subway), or build brand new infrastructure for surface rail, bus lines, or subways. for some areas, they won’t have the ridership to offset the envinromental impact – making the public transit worse for the environment.

Taiwan 2010-2011-0756.jpg

Now onto the other measure besides environmental impact. there is a laundry list of things this article avoids – with good reason. Yes, ridership is the primary determinant of the efficiency of the system to be environmentally friendly. but there are so many other factors involved in selecting public transportation. I think about new york city as the model of efficiency in US – it is a system that, although it is bleeding revenue, is one of the best in the world.

pro public transportation
– storage of a car in an urban environment is cost-prohibitive
– allows for more walkable city streets as you don’t have to expand streets to accomodate as many cars
– fewer parking lots in urban areas
– fewer cars on the road = fewer car accidents (maybe?)
– creates better access to areas across the city for people without cars, wider access to job opportunities
– cost of ownership of a car/maintenance

against public transportation
– scheduled times does not allow for flexibility, especially during off-peak hours
– some systems close, which does not allow third-shift workers to utilize,
– mass transit systems that are poorly designed cannot service the community
– depending on security measures, public transportation puts you at more prolonged risk of petty theft

so what’s the best thing people can do?
Dubner says “if we can persuade more people to leave cars and move onto the existing transit system that we already have, that’s a complete win for the environment”. some of the things lawmakers can do to help encourage mass transit use is increase highway tolls, increase parking taxes, and increase gas prices. — with the big caveat that hopefully these lawmakers are looking at the environmental efficiency these systems have.

and to finish off, the onion reports “98 percent of US commuters favor public transportation for others”.

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  1. Posted November 19, 2012 at 10:01 am | Permalink

    Rode my bike to work today, which consumed virtually NO gas or electricity (unless you count the electricity to make my morning coffee and the keyed entry to the bike storage cage), required only 1 passenger to be efficient, and cost $0 (excluding sunk costs). Three cheers for biking!

  2. Posted November 22, 2012 at 8:50 pm | Permalink

    yay! nyc is definitively full of people with the smallest carbon footprint!

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