elasticity
That assumes that all driving is discretionary, when in fact it's not. People have to get to work, and if they live in the suburbs they are unlikely to be serviced by public transport, so driving is effectively compulsory.
Commercial vehicles, likewise, cannot just choose to use a bit less, because the amount of transporting of goods is directly related to profit. If a business can't make a profit, it goes out of business, and THAT is where you will see the reduction in consumption coming from - mass lay-offs.
During the price rises of early 2007 to mid-2008, the price of WTI Crude Oil rose 72%, and consumption remained flat (instead of growing at 1.6% like the previous 20 years). Not much price feedback there.
