Some people worry about the slow turnover of the car fleet should oil availability to the US consumer decline rapidly over the next 15 years. They argue that even a crash programme to change over to hybrids wouldn't be able to save us, because even in 15 years half the fleet would still be non-hybrids.
My argument here is really a follow up on the CAFE post. While I think that CAFE is a poor measure to lower gasoline consumption in a low price gasoline environment, high gasoline prices without CAFE can work miracles.
They encourage driving fewer miles in smaller cars. For older fuel inefficient cars they impact the point where repairs are no longer justified, and so will lead to them being driven less and/or scrapped earlier. And they encourage a redistribution of the car fleet, with the most efficient cars getting used most, and the least efficient least. Suddenly the small third car (kept for occasional use by visiting relatives - my parents fall in this category, they've got three cars, and most of the time only 2 drivers, but just in case, they've got a third car) gets used for most journeys, rather than the posh, fuel inefficient SUV.
$10 per gallon will halve gasoline demand pretty quickly, 20% fewer miles, 5% of the fleet replaced by small high efficiency diesels that get 40-50 mpg, sell for $10,000 and would get preferentially used by those having to do a lot of miles, and the rest of the fleet redistributed a bit, and there we'd be in a year or two.
There's a point where gasoline demand does become very elastic. $6000 for 12000 miles at 20 mpg is a pretty good incentive to cut down on gasoline consumption. $20000 for 20000 miles at 10 mpg even more so, even for someone willing to plunk down $50000 for an SUV.