So what is the carbon footprint for one bus passenger traveling 180 mikes by intercity bus?
Well, the bus itself probably gets about 6 mpg, so, allowing for detours to stops along the way, that 180 mile trip probably burns about 33 gallons of diesel, or about 660 pounds of CO2 emissions. But how many passengers should I split that carbon footprint with? If I count the dozen or so average number of passengers I counted on the bus, I get 55 pounds – not much better than driving alone in a Prius (3.5 gallons, or 70 lbs CO2) or riding Amtrak (180 miles would be 81 pounds of CO2 based on the UCS average of .45 pounds per passenger mile).
That’s one of the problems of keeping track of your carbon footprint on public transportation – if you count the actual number of passengers on that empty bus or train, you can come up with some atrociously high carbon impacts for your public transport – driving you back into your personal car and negating the hope that public transit can significantly mitigate transport climate impacts. On the other hand, I don’t buy into the “that bus/train/plane was going there anyway so the carbon footprint of riding/flying is zero” cop out – if you are paying to be on the plane, bus, or train, you own your share of the impacts.
You could take the maximum occupancy to get some really attractively low footprint numbers. I could divide that 660 pounds of CO2 by the 50 seats on the bus and claim only 13 pounds CO2 as my personal share of that trip. But that is not really defensible – no public transit system cannot operate at 100% capacity all th time for every leg of every trip.
I can’t quite figure out the average ridership per bus for Adirondack Trailways – they claim to carry 3500 passengers on 142 trips each day, which would work out to about 25 passengers per trip – but clearly most passengers don’t ride for the whole “trip” – so the actual average is probably closer to the 12 passengers I observed.
I think I will just use the carbonfootprint.com calculator, which gives me 22 lbs co2 for the 180 mile trip by motor coach (.01 metric tons is 22 lbs). Incidentally, that same calculator gives a zero footprint for the equivalent train trip, which just can’t be right.
On the plus side, the bus was clean and pleasant and on time mostly. It even had high speed internet for a few hours. And it clearly beats the carbon footprint of train or driving alone – it’s just not clear by how much.