@AsEasyAsRiding Response from Sam Martin, the architect who came up with the SkyCycle idea:
London is not blessed with spare horizontal space..... It's streets pre date those of any of the cities you mention [CPH/AMS] & there is simply no capacity to include pedestrians (who are poorly serviced enough); buses; vans & eventually perhaps not cars & TfL's projection of tripling bike journeys from the existing 0.5mill per day to 1.5mill by 2020 to me speaks of an issue that needs to be resolved sooner rather than later.
Your thoughts are valid but london is neither of those cities & it is much larger than those cities with the need for vehicles to get into the centre of the city to service the city. It is an absolute necessity. End of.!