Economists will be in favour of road users paying what it costs to use their car – including the costs of pollution, other damage to the environment, and congestion. So I am broadly sympathetic to Alastair Darling’s proposals to charge road users. But I don’t understand why it isn’t simpler and less bureaucratic just to put up road fuel duty? (I would abolish the Vehicle Excise Duty at the same time.) Fuel consumption isn’t an exact measure of the full cost of a mile driven, but it must be a pretty good approximation. Are there really big enough benefits from using a satellite tracking system to charge by the mile, instead of charging per gallon of petrol used, to justify the huge cost?