A bus-free Oxford St is an idea without legs

The closure of Oxford Street, and its replacement by a tram, may well seem an improvement on the buschoked mess we have now. It may sound modern, green and Londonerfriendly. And it's always good for a clap at any Mayoral hustings.

But if any of the candidates stopped to think for 20 seconds, they would realise that pedestrianising Oxford Street is unworkable. As non-starters go, it is up there with a British Leyland-era Austin Allegro left out in the rain since 1981.

Even as I write the dreaded P-word, I can see those architect's drawings with their little blobby trees, happy stick-people and humming light-rail vehicles, employed on so many false London prospectuses over the years. The Millennium Dome! The Thames Gateway! Tower-block estates!

The problem, of course, is that Oxford Street's closure would devastate the bus service in central London. It's the main east-west artery for buses, with 18 routes. If it were replaced by a tram, everyone making an east-west bus journey would have to change twice.

And where would the trams and buses turn around? To create a tram-bus interchange at the Tottenham Court Road end, you'd need to knock down some buildings. To have one at the Marble Arch end, you'd need to put it in the park.

A little noticed feature of Ken's pedestrianisation scheme is to fund the tram by putting what he calls "two new commercial buildings, they could be another Selfridges or a modern office block" at the Marble Arch end. That's a bit more of the park gone, then. A decimated bus service, a decimated Hyde Park - what could be greener?

Pedestrianisation is often horrible anyway. Pedestrianised streets die when the shops close. They're yob magnets. They're suburban; they're provincial. Paving this street would symbolise the pasteurisation of central London, our rulers' desire to remove the mess and the noise and the life.

That's not to say that modern Oxford Street isn't horrible too, particularly if you're on a bus taking 30 minutes to travel it. This, however, is a problem entirely of TfL's own making. The buses on Oxford Street used to run more freely because they were Routemasters, and they were often half the length.

There were fewer of them, too. In the 1990s, long routes, such as the 8 and 10, were split, with the two halves overlapping in Oxford Street. Reunite those routes; scrap the bendies; put taxis on the parallel streets, where that option exists at the western end. Not sexy, perhaps, but the only workable option.

For all the supposedly vicious nature of the current Mayoral election, Oxford Street symbolises the campaign's essential fluffiness. What the candidates agree on makes a rather longer list than what they disagree on. Time, perhaps, for a bit more disagreement - and Oxonian intellectual rigour.