It's good to walk. So, on a recent trip to America, I set out on foot to find the nearest shops. The have-a-nice-dayer behind the hotel reception desk told me that the nearest mall was only 400 yards away, but that I couldn't possibly walk. I had to drive. Why? She was flabbergasted. Well, she said, in America everybody drives. I wish I'd taken her advice. There was no footpath, although the grass verge on the roadside was wide and flat. Dashing across the dual carriageway was more difficult: there was no pedestrian crossing. Even harder was the vast dug-out channel, a good 20 ft deep, that ran between the main road and the shops. It was clearly designed to keep anarchic non-automobilists at bay.

I recount this story because I think it helps to understand the mindset of Americans, and partly explains why Bill Clinton gave the green light to gas guzzling at last week's environment summit in New York. Americans simply will not countenance extra tax on petrol. It's a restriction on mobility. To Yanks, cars are how you get about. Legs are for indoors. And, what's just as bad - in a country that still hopelessly equates quality with quantity - the bigger the wheels, the better.

After a brief, unrequited fling with small(ish) cars a couple of decades ago - when it really did look as though the oil was running out - the Yanks are now back in their tanks, guzzling gas as though it's going out of fashion. The fact that petrol consumptive behemoths are going out of fashion in every other country in the world is irrelevant. No matter what his enviro-conscious daughter Chelsea may advise him, Clinton dares not raise gasoline taxes. It would be political suicide.

The new breed of Yank Tank is different from the old dinosaurs. The old breed were road-going aircraft carriers in both looks and manoeuvrability. The new breed are big, high 4x4s - which the Yanks tag "sports utility vehicles". Last year, their sales jumped 77 per cent in the US. To give you an idea of their size, the Range Rover V8, one of Britain's thirstiest cars, is one of the smaller SUVs.

The vast Ford Explorer, new to Britain and thankfully ignored by most buyers (as it is throughout Europe), is a medium-sized SUV in the States. Over there (but thankfully not over here) is an even bigger 4x4 Ford, called the Expedition. But even that's not big enough for the Yanks. Now there's news that Ford is planning an even grosser SUV. It will be almost 20 feet long, weigh nearly three tons and feature a 6.8-litre V10 engine which will return, at best, 12mpg. It will undoubtedly be one of the most profligate cars in history, if one of the most imposing. The Yanks will love it.

Despite booming SUV sales, even the American car makers want pricier gasoline. The Big Three - General Motors, Ford and Chrysler - have all lobbied the US government for higher prices. They're all multinationals, making cars round the world. They'd like nothing better than to standardise cars internationally - the goal behind the "world car" ideal.

But whereas Japanese and European cars get ever more similar - drawn together because both regions have similar socially responsible motoring priorities - the Yanks, with their absurd SUVs and pick-up trucks and gargantuan sedans, are playing another game. And they get away with it because, with gasoline at just over a dollar a gallon, there is absolutely no incentive to buy cars that sip rather than slurp their fuel. Petrol in America is rather like water used to be here before the water companies were privatised: never-ending and cheap.

Sooner or later, possibly when global warming has turned the heartland of America into a desert, and Portsmouth resembles Provence, the Yanks will come to their senses. Goodness knows. By then, folks may even be prepared to walk.

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