Welcome one and all, to the heart of London’s growing start-up district, Silicon U-bend!

So what’s going on here? Transport for London (TfL) is proposing to close the north-western arm of the Old Street roundabout and open it to two-way traffic: effectively turning it into something that works more like a series of T-junctions. It’s a trick they’ve used before at the southern roundabout at Elephant & Castle.

In return, you’d get a new public square (though whether anyone wants to hang out in a peninsula surrounded by exhaust fumes remains to be seen). You’d also be able to get to Old Street station without entering those subways which are always so welcoming at night when the pubs are kicking out.

Best of all, TfL says, it’ll make it possible to create segregated cycle-lanes, with their own traffic signals.

The downsides, other than the inevitable disruption while building work is taking place, would be that it’ll become a complete pain in the backside to drive from Old Street in the west to City Road in the north, and you’d be banned from turning right to go south altogether. That would probably drive some traffic onto other roads further west.

Click for larger version.

So, why can’t they turn the whole thing into a crossroads isntead? TfL claim that the volume of traffic would mean that any potential crossroads would need to be enormous, and so would take ages for pedestrians to cross. It’d make it harder to create step-free access to the underground station, too.

But they’ve used other excuses in the past. As a spokesman for the Hackney Cycle Campaign told the Hackney Citizen earlier this year: “TfL has given various reasons for opposing a crossroads over the years, varying from traffic capacity to the location of sewers and lifts, but no detailed evaluation of the option has ever been published.”

There is one other possibility: the busiest area of any possible crossroads would be directly above the ticket hall of Old Street station. There might well be very good engineering reasons why you don’t want several thousand heavy vehicles an hour driving over it.

TfL is consulting on this plan until 22 December. If it goes ahead, construction will begin next year.