Frankfurt: what does green really mean? - Conclusion

While there's no doubt that not all manufacturers put the same amount of effort into presenting green models at the Frankfurt motor show, they will all leave with a pretty clear understanding of where, broadly, the industry is heading.

That in itself should accelerate the process of investing in, creating and putting on sale cars with even greater emission improvements.

There is a note of caution to sound, however, because it was also clear that there is still no unity of thought on what is the best way forward.

Could it be ultra-refined petrol or diesel engines? Costs and limits as to what can be achieved make that unlikely.

So will it be hybrid engines? If so, will they be petrol-, diesel- or hydrogen fuel cell-powered? It's a giant leap forward, but few feel it is the ultimate solution.

So maybe the electric cars, with ranges now pushing more than 60 miles, will be the answer? Possibly, but it won't happen without a huge leap in consumer attitudes.

Perhaps, then, the 2007 Frankfurt motor show was just a first step.

Now we know the future's green, but we just don't know what shape it's going to take.