High gas prices mean less demand and less pollution at least in theory, right? Not necessarily, finds Mark Jansen. Our relationship with our cars is far more complex... High petrol prices are bad news for drivers, which means almost all of us, but those who care about carbon emissions may see some good in all this. Surely, the logic runs, if petrol prices are soaring, more car owners will use public transport instead, drive less and walk more, buy smaller and more efficient cars? By the same token, won't high petrol prices stimulate the development of alternative fuels? Sadly, it doesn't work that way. Repeated studies have shown that petrol price rises have only a tiny impact on demand. The cost of petrol is comparatively low compared with life's other necessities, and rising incomes over the last 40 years have reduced petrol's share of household budgets. This is borne out by the continuing increase in car ownership in the UK. Transport experts even suggest that petrol prices would have to double before there is any discernible impact on carbon emissions.