I was prompted by his recent blog post about our transport emissions to do a little thinking of my own.
Rowlatt was trying - bravely if I may say so - to make a cold-hearted assessment of the relative carbon emission impacts of different modes of travel, and to dispel some of the lazy assumptions. So, for example he found that, on a grammes of carbon per passenger kilometre, one person in a car, a virtually-empty bus or a half-empty train were all at least as bad as flying; and that if you travelled everywhere in a fully laden car you would be giving half-empty trains a real run for their money.
His 'good science' message was, don't just assume that getting a train is a lower carbon option, but think about the full picture. He also had a 'pragmatic logic' message, which was that we should use public transport anyway, because the services will run anyway and by using them we are removing our car emissions and also reducing the emissions per passenger kilometre of the bus or train, by increasing its patronage.
In a sense, I'm with Ethical Man on this, but his rather easy answers to tricky questions left me uncomfortable. After all, isn't "it was going anyway, with or without me" a stock excuse for taking a flight? Hell, I've used it myself. Sure, there's a difference, because if a scheduled flight was regularly empty the airline would withdraw the service, whereas buses and trains are specifically obliged to run services during low-demand times in order to maintain the concept of 'public transport'.
In reality, of course, trains in the UK are becoming so stretched for capacity that finding one that's half-empty is quite an achievement, and pricing structures have been cleverly (if irritatingly) designed to spread passengers across off-peak times. Buses are a bit different, because they do often run quite empty but also seem to burst unhelpfully at the seams whenever there is anything approaching a rush-hour.
Anyway, Ethical Man's analysis set me thinking: perhaps counting our grammes per passenger kilometre isn't actually the best way for us to plan on how to reduce our carbon emissions. Although on the face of it it's the most straightforward calculation, when you look at the variables (how efficient is my car, how full is the train, was the plane going anyway, etc) it's pretty difficult to say with confidence that we've made the best choice for the journey in question.
For a start, the greenest way to make a journey is of course not to make it at all, but that can be inconvenient or just rather unsatisfying. "Darling, let's go out somewhere today - how about going to the market in Buxton?" "No dear, think of the carbon emissions. Let's stay in and watch the lettuces growing in the garden."
No, the more I think about it, the way to think about transport emissions is to think of transport not as a series of thousands of individual choices, but as - dare I say it - a service. Let's say there's a train service running every hour between Sheffield and Leeds for 20 hours a day, with space for 200 passengers. 5 of those trains are full, 10 are half-full and 5 are virtually empty. So 20 trains are transporting just over 2000 passengers. Immediately we can see that spreading passengers from full trains onto half-empty ones won't make any difference. There are only three ways of reducing the per-passenger carbon emissions of the service:
1) carry more passengers in total;
2) make the trains more carbon efficient themselves;
3) withdraw low-demand trains from the service.
The third option is controversial and potentially counter-productive in the long-term, so even though it looks like an inefficiency it may be worth putting up with. The first two options are not controversial but do require all sorts of imaginative solutions, such as how to get commuters to travel at different times instead of travelling by car, and how to make railway vehicles more carbon efficient without vast expense on new rolling stock.
Thinking of each mode of transport as a service to society, rather than as myriad separate choices, has to be helpful, because you can start to see the particulars of each mode. For example in the road-freight industry there must be huge opportunities to tackle the problem of vehicles running empty on return trips: you could actually increase volumes of freight movement and reduce transport-related emissions simultaneously.
Now, how do we apply this to private cars?.....
AW.
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