Go for it Thorners!

I'll bet the idea of cycle lanes above the rail tracks came from a non-cyclist. Just imagine the steepness of the ramp you'd need to get up there... and then what you'd do each time the train went through a tunnel.

Building cycleways alongside any new stretches of track might be quite pleasant though.

Or build tunnels for the South Circular and major trunk roads (a Cross-road project) and send the heavy through traffic underground, leaving the upper streets for pedestrians, bikes and slower local traffic, reclaiming our streets for local communities.