Scrappage laws like "Cash For Clunkers" are meant to stimulate the economy and cut down on greenhouse emissions by providing an incentive for consumers to trade in older, more environmentally-unfriendly vehicles for newer, more fuel efficient vehicles.
Unlike other European countries that hate old cars, the UK didn't bother to put limitations on price, consumption, or emissions of the cars purchased under the scrappage laws, so you can trade in your junker and get a Cadillac Escalade if you like. Two noteworthy hoons traded their cars in on a pair of Nissan GT-R's which, under the best possible conditions, could get 21 MPG if you could keep your foot off the yeehaw pedal. That consumption puts it in the highest tax bracket for emissions, something like the US gas guzzler tax. This is a perfect example of why scrappage or "cash for clunker" incentives are silly. The free market has already established a time honored life-cycle for a car, and interrupting it with an unnatural incentive for scrapping it before its time is just asking for trouble, especially if those incentives are paid for with tax dollars. Not to mention it puts sweet old steel in peril for no good reason. [AutoTrader]