Roundabouts like the ones used in the Netherlands separating cars from cyclists could be used in London as early as next year, the city's cycling commissioner has said.
Trials of the layout are taking place at a research laboratory in Berkshire.
The roundabouts do not conform with Department for Transport regulations as they stand.
But Andrew Gilligan said if the trials continued to go well they could be seen in 2014.
'Fantastic for cyclists'
The layout gives cyclists priority and means they are in the line of sight of drivers when vehicles exit the roundabout.
Campaigners have called for a number of London junctions to be changed to make them safer following cyclists' deaths.
In 2011 two cyclists died in the space of three weeks at the Bow roundabout in east London.
The roundabout trial, which has been going for six weeks and will end in July, forms part of the mayor of London's Vision for Cycling.
More than 600 people have been involved so far and the effects on safety and capacity will be studied.
The impact on pedestrians and lorry, van and car drivers will also be monitored.
Members of the public can participate in the trials.
Other ideas being tested include traffic lights with separate signals for cyclists.
Mr Gilligan said: "We've got a cycling budget of £913m over 10 years and it includes £100m to refit junctions.
"I'm really looking forward to seeing this [roundabout] on the road. I think it's going to be fantastic for cyclists."
Subject to the outcome of the trials, Transport for London (TfL) will work with the Department for Transport to try the roundabouts on the public highway.
TfL said improvements at Bow roundabout and a 20mph speed limit at Waterloo roundabout were due to be delivered this summer as part of ongoing improvements.