We have an image of the American motorist, his big flobbery stomach, flobbering from state to state in a big, flobbery car with big flobbery suspension at a flobbery 55mph. For many years, I've argued that the heart of the average American motorist beats approximately once every 15 minutes. Technically, they're in a coma. But, sadly, this is wrong.

Nowadays, the American motorist drives at the same speed we do, 80 or 85. And he's the most aggressive creature on earth. If you wish to change lanes on the freeway, because, say, your turn-off is approaching, you can indicate all you like, but no one will slow down to let you in.

They won't speed up, either. They'll just sit there until you remember you're in a rental car and make the move anyway. Then you'll get a selection of hand gestures that you never knew existed. I know of no country in the world where motorists are so intolerant of one another.

The slightest mistake causes at the very least a great deal of horn blowing and, at worst, a three-second burst from some kind of powerful automatic weapon. Then we have the question of tailgating. Of course, this happens elsewhere - I've actually been nudged by a nun in Italy - but there's nowhere it happens so often as on the American freeway.

Everyone sits as a matter of course about three feet from your rear end. Which, when you're being followed by a Kenworth truck and you're doing 80, and he has an M16 carbine, and you need to turn left, and the person on your inside won't let you in, can be a bit unnerving.

It isn't how they drive that's changed, either. It's what they drive. Now, for every nondescript Kojak-style saloon, you'll see two Evos or Subarus. And almost every car has been modded in some way. My favourite was an orange Lotus Exige parked at the pumps in the middle of Death Valley.

"Yeah," said the rather serious-looking driver when I approached, "I've given it two degrees more camber on the back, fitted a 25 per cent softer compound on the front, uprated the supercharger..."