Detroit motor show: green and mean - Introduction

This year's Detroit motor show definitely had a green message - sadly, though, it was never quite clear exactly what this message is.

On the one hand, there were launches of gas-guzzlers such as the Ford F-150 and Dodge Ram trucks, both of which continue to be huge sellers in America.

Then there were the sportscars, such as the 620bhp Corvette ZR1 and Lexus LF-A Roadster, that stick two fingers up at environmentalists at 200mph.

On the other hand, there were Chrysler's three eco-concept cars, the announcements that even Hummer and Ferrari were investigating biofuel and a raft of announcements about forthcoming diesel, hybrid and plug-in models.

And quite where Audi's R8 V12 TDi Design Study fitted into all this, offering supercar performance at 24mpg, nobody quite knew.