The Frankfurt show is always an opportunity for the German manufacturers to show off in front of a home crowd, something they need little encouragement to do. And it never takes long for things to get competitive. In previous years this one-upmanship has mostly been directed at the creation of impossibly complicated stand displays and vast arrangements of the corporate line-ups. But this years the fight is definitely over which is the greenest.

And it's not just at the level of eco-concepts like the stunning BMW Vision ED: it seems like pretty much every car on the show floor has been labelled with its fuel economy and CO2 figures as the rival companies' various enviro sub-brands battle it out: Bluemotion, Bluetec and Efficient Dynamics. It's all useful progress, no doubt, but the competitive greenery is starting to feel samey. The conflict was exemplified by a near-collision I witnessed between BMW 320d and Mercedes E-Class Bluetec media shuttles as they battled to demonstrate their abilities to waiting journos.

Which is why I'm thankful for the French manufacturers' considerably wackier efforts at planet-saving. Renault's deserves serious respect for having the corporate guts to hang its future around the four electric concepts that dominate its show stand.

And I've still got a sneaking regard for those manufacturers who don't even pretend the environment is an issue for their well-heeled clientele: prime exhibit, the Lamborghini Reventon Spider.