Cost-benefit analysis

Christian Wolmar (Transport Times, December 2nd) is surely experienced enough to be unsurprised at the changing figures for the costs of UK congestion, varying between £6 billion and £20 billion apparently according to fashion.

All you have to do, as with so much cost-benefit analysis, is to remember which side of the equation the figure is.

So if you want somebody to give you money - for road building to "relieve congestion", for example - you come up with a nice big figure for "the costs of congestion", even if you know perfectly well that congestion levels will remain the same after your road building is completed.

If, on the other hand, you think that motorists cause congestion, and that they should pay for this and their other external costs, then the figure declines or disappears altogether.

It depends which side you are on, and in the transport policy world we live in I think it is pretty clear which side rules.

Dr. Robert Davis
Road Danger Reduction Forum
PO Box 2944
LONDON NW10 2AX