London may be getting a new east-west Cycle Superhighway soon, but that hasn’t stopped a team of architects from proposing a second one.

And whereas Boris’s route will run along the Embankment in place of a traffic lane, this one is rather unusual: it’s conceived as a ‘floating deckway’ along the South Bank of the River Thames.

The £600m Thames Deckway would run from Battersea to Canary Wharf, a seven-mile floating cycleway with regular links to the shore. Because the Thames is tidal through central London, the plans envisage a pontoon that would rise and fall with the tide.

The route has been devised by architect David Nixon and ‘space entrepreneur’ Anna Hill. As yet it remains just a proposal, but they claim to have signed up construction giant Arup as part of the River Cycleway Consortium. The deckway would be funded by private sponsors and by a toll of £1.50 per journey. Dezeen quotes the promoters outlining their intention:

“London needs to think outside the box of conventional solutions to solve its deep-seated traffic and pollution problems. The Thames offers vast, untapped potential to ease and improve London's infrastructure problems. What is needed is imagination to unleash it.”

But such a route will need more than imagination to overcome the physical difficulties. With frequent ferry services, commercial barges and leisure traffic along the Thames, any floating cycle route would need to weave behind the piers built for existing river users.

There are docks at Rotherhithe to negotiate, not to mention the HMS Belfast. The reaction of riverside attractions and property owners to a new, modern-looking imposition on their ‘moat’ can only be imagined. And then there’s the challenge of the eastern end: how would cyclists cross from the south bank of the river to Canary Wharf and the Isle of Dogs?

The Thames Deckway is the latest of several fanciful proposals for futuristic cycleways in London. Architect Norman Foster proposed elevated cycle paths above the city’s railways, while a design competition advocated a raised route above the historic Regent’s Canal – an idea quickly dismissed as “potty” by the Canal & River Trust.