Credit: Foster + Partners

Has London reached peak car? This is frequently asked question usually reflects a pessimistic (okay, realistic) assessment of the state of London traffic. One followup question might be: How much is London prepared to pay for an alternative? The answer could be $12 billion—the potential price tag for a solution proposed by Foster + Partners, Exterior Architecture, and Space Syntax.

The SkyCycle, a proposed network of elevated bicycle paths, may constitute the world’s first major infrastructure project for bicycle commuters. Although it made a splash when Foster + Partners announced in January that it is involved in the project, the SkyCycle is an idea that Exterior Architecture has been kicking around for a while, one that makes sense based on the number of people it would serve. London authorities and the designers estimate that half of the 6 million people who reside within the network’s catchment area live and work within 10 minutes of a proposed SkyCycle entrance. The network has been designed accordingly: It will accommodate up to 12,000 cyclists per hour, per route.

Despite the gee-whiz factor of cyclists soaring through the city on an elevated track—the renderings nearly summon images of the light bikes from Tron or the Rainbow Road from Mario Kart—it's a fairly commonsensical proposal built on the bones of an older transit network. The SkyCycle’s backers are planning it as a low-cost, low-impact development that exploits existing industrial corridors. Many of the proposed SkyCycle tracks follow existing railway lines; since these were largely designed for steam engines, they avoid steep gradients or turns that would make a cycle track unfeasible. Foster + Partners describes wide-scale deckbuilding along largely undeveloped rail corridors as an opportunity for commercial regeneration in industrial areas. An elevated network solves another problem: London’s rapidly rising mortality rates for cyclists.

That part is controversial, actually. Exterior Architecture's Sam Martin told Henry Grabar at The Atlantic Cities that some London bike enthusiasts have complained that instead of segregating cyclists and drivers, London should focus on educating drivers on sharing the road with cyclists. After all, cyclists would still need to take London's streets for every trip they took on the SkyCycle; fewer bikers on the streets during rush hour might lead drives to be less aware of cyclists around them. London roads would require no fewer bicycle lanes even if the SkyCycle were built.

It's another aspect of the SkyCycle that is likely to lead to more objections, though. The costs for building the SkyCycle are up there: A 4-mile trial stretch might cost $363 million to build, according to an early study. If that's representative for the costs of building the whole 137-mile network, then it could cost some $12 billion. Is London prepared to pay that much to alleviate traffic?

One way to think of it is as a redistribution scheme: Commuting costs represent a "cost-of-living crisis" for Londoners in lower income brackets, according to a study written up by The Independent. Surely a major commuter bike network would promote physical fitness in the face of rising obesity and diabetes rates. But its backers might suggest that the costs for inventing in the SkyCycle are lower than the costs of doing nothing.