It's hard to tell what would satisfy.
I've pointed out that over a 30 year period that has seen the RPI more than double and the costs of public transport rise by 50% - in real terms - the cost of private motoring has fallen by 10%.
I've explained that the pre-dominance of the private car isn't the normative, spontaneously arising natural order of things, but a consequence of generations of political decision making favouring the car; "the americans are rich, let's copy them". I've shown that where investment is spread more equitably between different modes of transport, modal shifts in personal transport are achieved. For reference, beard, view the linked to clips on the "Cost of Motoring" thread.
I invited you to multiply the cost to the tax payer per road traffic casualty - an average of £70,000 - by the yearly number of road traffic casualties; 271,000. Please note this doesn't include the broader health bill that includes the @38,500 annual premature deaths from road traffic air pollution, or that proportion of the @45,000 deaths from CHD attributable to sedentary life choices. Nor have we touched on the costs to us all of the obesity epidemic, the rise in type 2 diabetes and other attendant health risks.
Then.. Well look, broadly, I find this sort of analysis more compelling that the anecdotal peevishness of safespeeders:
http://www.igreens.org.uk/great_road_tr ... ubsidy.htm