Buses are the greenest choice for short trips
By Laura Lynch
Here’s a quick question. Which is the most energy efficient form of transportation from Washington, D.C., to New York City: a car with two passengers, an Amtrak train full of people, or a loaded bus?
When Sunil Somalwar, professor of physics at Rutgers University, brought up the subject to an online environmentally savvy group recently, we all assumed that the train was the answer. We were wrong.
The standard for comparison across modes of transportation is “passenger miles per gallon,” which is calculated by multiplying the number of people a vehicle can hold by the miles per gallon the vehicle gets. For example, if a hybrid car gets 50 miles per gallon and carries one person, the passenger miles per gallon equals 50. If two people are in the car, the passenger miles per gallon double to 100.
Most cars, of course, get far fewer than 50 miles per gallon; the average is closer to 20. So even if there were five people on the trip, the average car would reach only 100 passenger miles per gallon.
Do Amtrak’s trains fare better? Dr. Somalwar did some calculations and determined that, because of the heavy weight of the trains – 2 tons per seat on the newer Acela cars – the passenger miles per gallon are low. His estimate is that Amtrak averages approximately 30 passenger miles per gallon, assuming that every seat is occupied. NJ Transit trains probably fare a bit better.
But the winner in this competition is the bus, with a range of 130 to 200 passenger miles per gallon. And, as it turns out, we are fortunate to be living in a bus-rich region. According to the Tri-State Transportation Campaign, each weekday more than 9,000 buses cross the Hudson River into Manhattan, carrying twice as many passengers as commuter rail does. Discount bus lines cost a tiny fraction of what Amtrak charges, and taking the bus removes the hassle of paying for tolls and finding a parking spot in the city.
Dr. Somalwar left us with one more comparison: the amount of fuel for two passengers on a trip from central New Jersey to Washington, DC. His 1993 Honda Civic, at 60 passenger miles per gallon, uses 3 gallons of gasoline per person. Amtrak uses approximately twice that amount. A bus, even though it gets a mere 4.2 miles per gallon, when full of people uses only 1 gallon per person for the trip.
There’s one more environmental advantage to taking the bus: Most electricity is generated by burning coal; coal burning emits more greenhouse gases than burning gasoline does; and most trains in our region run on electricity. Until we move to clean, renewable fuels all around, the greenest option for short-distance trips is to take the bus.
For more information on fuel efficiency across modes of transportation, see http://airfare.michaelbluejay.com/modes.html and http://en.wikipedia.org/wiki/Passenger_miles_per_gallon. To learn more about the future of bus transportation in our region, see Tri-State’s transportation report at http://mobilizingtheregion.files.wordpress.com/2009/05/pa-report_final.pdf. Sunil Somalwar’s presentation on transportation’s environmental impact can be found at http://www.physics.rutgers.edu/~somalwar/energy/REI09/0905-REI-Somalwar.pdf. To learn more about sustainability go to http://sustainablelawrence.org.