Are walking and cycling as green as we imagine?

The other issue is that cars look relatively good because the comparison is on a per kilometre basis. The emissions associated with the manufacture and disposal of cars are averaged over thousands of kilometres annually whereas the sort of trips where you could walk instead of drive might amount to hundreds of kilometres per year.

There’s an irony in cars looking relatively better as the number of kilometres of driving – and hence the consumption of fuel – increases! There’s a natural limit to walking so pedestrians use local facilities and make fewer trips than drivers; the difference in the kilometres travelled by walkers compared to drivers is an order of magnitude; and so, therefore, are their emissions.

This is much the same logic as I discussed some years ago in relation to shaky comparisons between driving and public transport; see Is “per passenger kilometre” the right metric for comparing modes?

Yes, it’s very important to understand the emissions implications of diet; it’s not just down to how we travel and the spaces we live in. The issue is to change the way you eat as well as the way you travel. Walking and cycling are the way to go when it comes to reducing emissions.