LA: exporting green tech to the world? - Introduction

Arnold Schwarzenegger, former movie star and now the green-campaigning governor of California, did a photo-call in front of six cars designed to comply with the state's tough emissions laws at last week's Los Angeles Auto Show.

The most remarkable thing about the event was how little those six cars had in common.

There was a bioethanol-fuelled Audi, a Chevrolet electric concept car, a dual-hybrid Dodge, a Honda fuel cell car, a Toyota plug-in hybrid and a clean diesel Volkswagen.

On the one hand, you could say that it shows the diversity of potential solutions in the quest for cleaner cars.

On the other, it illustrates the difficulties manufacturers face in trying to find the best way of overcoming our dependency on petrol and diesel.

In effect, car makers are having to back every horse in the race in an effort to find a winner - and this inevitably means research and development budgets are spread more thinly, so reducing the chances of a big breakthrough.