Close ned but it's not just 4x4's that use pointless amounts of fuel.
We just simply need to stop approving the sale of any car that can't demonstrate say 40mpg.
It'd have to be done at the European level but it's been done before with catalytic converters etc.
OK Jeremy Clarkson would have a blue fit but I''m sure his favorite sports car companies would quickly develop an economy mode.
Incidently it's not just me the head of Shell agrees (although I think 35MPG might be a little unadventurous)
http://news.bbc.co.uk/1/hi/sci/tech/7225451.st m