The proposed network would follow existing suburban rail services, providing routes which can be accessed at over 200 entrance points and connected to the street via ramps and hydraulic platforms.
Almost six million people live within the catchment area of the proposed network, half of whom live and work within 10 minutes of an entrance. Each route can accommodate 12,000 cyclists per hour and will improve journey times by up to 29 minutes, Foster + Partners says.
With the capital's transport network already at capacity and with population growth to set to grow 12% over the next decade, the congested city faces a growing challenge.
"The environmental and health benefits of cycling notwithstanding, the bicycle is a more efficient use of London's limited space - we believe there is a pressing need for network modelling of new capacity for these active, self-determined modes of transport," Fosters + Partners said.
The London-based firm got involved late in 2012, wanting to build on Sam Martin from Exterior Architecture's initial development for a trial 6.5km route from Stratford to London, Fosters + Partners' partner Huw Thomas said.
"We could see there was greater potential," he said, adding that Space Syntax, with whom the firm has been collaborating for 25 years, expanded the model to cover the whole of the city.
Over the past couple of years, the firms have been working together to determine which routes would be the most beneficial and what that would mean for travel times into London compared to commuting by bus or tube.
If approved, the project, which is backed by Network Rail and Transport for London, could be completed within 20 years, Thomas said, likening it to the scale of the city's Crossrail development.
SkyCycle would be able to exploit the historic legacy of London's railway lines - originally built for steam trains, they follow contours that naturally reduce the amount of energy expended and avoid steep gradients, making them ideal for cycling.
Furthermore, early studies show that the SkyCycle system provides capacity at much lower cost than building new roads and tunnels. The possibility of the wide elevated cycle deck providing development opportunities for businesses along the route, particularly where it intersects with stations and bridges, has also been the subject of the study, exploring ideas for public/private commercial growth and regeneration.
The aim is to make this much more than simply "an arterial centre for cycling", Thomas said, referring to the large potential for adjacent property development.
However, before the project can move closer to reality, there are several questions which need to be answered with respect to the planning regime as it is such a new system. Does it need a development consent order, for example, and what would the planning legislative process entail? Furthermore, finance remains a major issue, with designers currently looking for funding for a feasibility study.
But, despite some misconceptions to the contrary, the firms do not want to draw the focus or funding away from improving safety for cyclists on the roads, or indeed to take them off the road. Rather, SkyCycle would deliver additional capacity, helping to integrate cycling into the urban realm, Thomas said.
Six cyclists died in road accidents in a two-week period last November, bringing the annual total up to 14.