So here in Boston we have moved from a two car commuting family to a single car that is used for incidental activities rather than regular travel. The kids walk to school while I walk and catch the bus to work. Even though it is the dead of winter I have actually sustained this new routine mostly due to the ability to work on the bus with my iPhone. The exercise is doing me good and at some level I am supposed to think I am contributing to the environment.
I also listen to podcasts on the bus as I did when I drove to work. So it was of some surprise that I listened to a recent episode of Tim Harford’s More or Less (while on the bus) about the environmental impact of bus as opposed to car travel. Tim repeats the issue in his FT column today.
According to my colleagues on the BBC’s More or Less programme, cars emit 127g of CO2 per passenger per kilometre and buses 106g, based on average occupancy. Even London buses average a mere 13 passengers.
Add my additional walking to the equation and my emissions may well be higher as a result of this change in activity. Indeed, as I like to work on the bus, I prefer to avoid the crowds. So on the bus I catch at 6:30am there are rarely the average number of passengers.
So what is the environmentalist’s response? It is that the bus “would be running anyway.” The idea is that buses have a regular schedule and so there are going to be times where they are more empty than full and other times where the reverse is out. So the appropriate thing is to look at the marginal rather than the average to work out net impact. As the bus is running anyway but a car would not, buses win.
Tim Harford points out, of course, that the same is true for air travel. Air travel is, for the most part, public transport. So the same argument applies to it: “the plane would be going anyway.”
An admittedly unscientific poll of environmentalists at dinner parties suggests to me that they think “the plane is making the journey anyway” excuse is unacceptable but “the bus is making the journey anyway” excuse is spot on – and that they have no coherent justification for the distinction. Their favourite excuse is “you have to set an example” – but surely, before you decide to set an example, you need to be sure that you aren’t setting a bad one.
The resolution lies in a very tortured argument.
For all you environmentalists out there, then, here is the justification for the double-standard of taking the bus but not the plane: it is that bus schedules might be insensitive to passenger demand, while planes are highly sensitive – and ever more so since the budget airlines arrived on the scene. Your best argument for taking the bus is a perverse one: that, no matter how many people do likewise, it’s the rare public transport tsar that will lay on extra buses.
The idea is that airlines and bus authorities put on buses to match demand. But airlines are in a competitive market environment while buses are managed by public authorities who are really bad at putting on extra buses. I’m not sure what the empirical evidence really is for that potential out but it strikes me that it could also go the other way. Public authorities have trouble cutting the 6:30am bus that a private company would happily do away with. In some countries, buses don’t leave until they are full — that is the market system at work.
This all suggests that just like we have ‘time of day’ airline pricing we need ‘time of day’ bus pricing. I should pay for travelling on my average emitting bus more than I would pay for stuffing myself into a crowded one. The interesting question is whether I would end up contributing to emissions less once all of this is in place. For the moment, there is no reason for me to be smug but I do enjoy being able to work while commuting.