When Buying a Hybrid Isn't Green

If I were ever to have a nice little place in the Hudson valley (a chap can dream), I'd need a car to keep at the train station while I was in the city and to run me into the nearest town when I was in the country. As a good environmentalist, what car should I buy?

I'm pretty sure the answer is an old gas-guzzling pickup truck or, something along those lines, rather than a sexy new Prius or Smart. So long as the old gas guzzler is going to be driven by someone, it should be driven by ultra-low-mileage me, rather than someone who will burn up loads of gasoline driving it.

In general, from an environmental point of view, the best place to keep things like Porsche Boxsters and Land Rovers is in a garage, unused, rather than on the road, belching carbon. Paul Wilmott explains, at the expense of Iain Banks:

The Scottish author Iain Banks, a famous petrolhead, recently sold his collection of classic cars and replaced them with a single hybrid. He used to have a Porsche 911 Turbo, a Porsche Boxster S, a BMW M5 and a Land Rover Discovery. And he bought a Lexus SUV hybrid instead.
Am I alone in thinking this counterproductive?
First he says that he's getting about 28.5mpg out of the Lexus as opposed to the "low 20s" he got from Porsches and the BMW. See what I mean? The marginal improvement probably did not outweigh the damage caused by the manufacture of the Lexus in the first place.
And, second, it is not humanly possible for Iain Banks, brilliant author though he may be, to drive more than one car at a time. So now there are five gas-guzzling cars on the roads, possibly all at the same time, when before there was just one.

Pay no attention to the mileage figures, which use UK gallons rather than US gallons and which therefore can lead you astray: the argument doesn't rest on them.

But if you see two drivers in Berkeley, and one's driving a Prius while the other one is driving an old second-hand gas-guzzling Volvo, it's not at all obvious which one has made the greener choice of car. After all, if you sold the Volvo and bought a new Prius, wouldn't total emissions rise, thanks to the carbon footprint of the Prius itself as well as the continued emissions from the Volvo?