A review of all junctions on London's cycle superhighways has been ordered following the deaths of two cyclists within a month.
The news comes as around 200 cycling campaigners held a vigil for the victims - Brian Dorling, 58, and a 34-year-old woman - at 18:00 GMT at the Bow Roundabout.
Mr Dorling, of Hounslow, was killed on 24 October while the woman cyclist died on 11 November.
Kulveer Ranger, Mayor Boris Johnson's director of environment, said London is seeing "unprecedented levels of cycling" and Transport for London (TfL) is looking into the issue of safety.
He said: "Work is beginning on how London gears up to move to the next level of cycling infrastructure and continuing to improve safety for cyclists.
"This includes a commitment from TfL to review all major schemes planned on TfL roads as well as to review all the junctions on the existing cycle superhighways.
"That work will include an assessment of Bow Roundabout, which TfL have been asked to report back to the mayor on as a matter of urgency."
'Unclear and difficult'
More details have also emerged about the recommendations made to TfL about the junction.
I have been given a document written by the Jacobs consultancy for TfL prior to the installation of Cycling Superhighway 2 (CS2).
It highlighted some problems cyclists could face, including "high traffic flows and speeds on Bow Roundabout" and the view that "continuation to and from the cycle route is unclear and difficult".
The recommendations about what should be done are very clear.
The document says Toucan crossings should be installed on the north and south sides of the roundabout.
And "off-carriageway cycle lanes" should be provided around the roundabout, to "encourage less confident cyclists to use the route".
Neither of these were acted on in the implementation of CS2. So someone made a decision to ignore the advice of TfL's own traffic consultants.
The Greens on the London Assembly say they now want a clear and honest account of who made the decision not to proceed with these changes, and whether either the mayor's advisers - or mayoral direction - influenced the choices made.
The Greens made it clear, as I mentioned in a recent article, that they believe the smoothing traffic flow policy has affected the decision.
On Wednesday that was denied by Mr Johnson who said any decisions on this roundabout had not been referred to him.
Ashok Sinha, from the London Cycling Campaign, said: "These documents show that Transport for London were clearly advised by their own consultants, as well as the London Cycling Campaign, to provide safe signalised crossings and off-carriageway cycle lanes at Bow Roundabout.
"The mayor has to explain why these measures were not carried out.
"We are calling for an immediate re-design of the junction to reduce the road danger and prevent any more tragic deaths."
According to John Biggs, the Labour London Assembly member for City and East, we will know within a week the results of TfL's safety review of the junction.