Putting traffic lights on the exit of a roundabout is absolutely contrary to the principles of a roundabout, they can only work if there is a pedestrian phase. e.g. chiswick roundabout where the concept is much closer to Davids idea as there pedestrian and cycle routes through the centre of the roundabout.
Yes, but large roundabouts without lights don't work well with heavy traffic, so traffic lights are already used quite a lot - some (not enough) with a flashing amber mode for late nights.
I reckon the combination of cycle-lane removal at junctions, "early green" traffic lights for cyclists, and greater enforcement for driving offences will save lives. Peculiar alternative routes for cyclists should only be needed at huge junctions. The junction in question isn't huge and isn't currently much out of the ordinary, apart from the stupid cycle lanes that encourage dangerous positioning.
Roundabouts have a design capcity, it is higher than the equivilent junction as a traffic lighted cross roads, however once the capacity is exceeded then the capacity drops of massively. Traffic lights by contrast maintain their maximum capacity once the demand exceeds it. In most cases you only see traffic lights retro fitted to roundabouts at the entrances to a roundabout and on the roundabout itself they are not on the exit sliproads as whilst this reduces the peak capacity of a roundabout it is then maintained even when exceeded as the traffic is prevented from entering the roundabout. Roundabouts like this work well until one of the exit arms jams back onto the roundabout itself when the whole system collapses.
I don't know the Bow roundabout but would suggest that it is probably simmilar in traffic volumes to Chiswick roundabout (A4 A406) junction which is overflown by the M4 elevated. At this location the traffic lights at the entrances and on the roundabout are used to get pedestrians to the centre of the roundabout and then out to their exit by combining a green pedestrian phase with the red traffic phase. Where pedestrian lights are provided across the exit lanes they are set back from the roundabout to reduce the risk of the traffic queueing back onto the roundabout and are only really provided to enable crossing of one arm any further travel round the roundabout is intended to be via the centre.
Changing the deflection angle is to slow down traffic on a free flowing roundabout however this is already achieved by the red lights and traffic volumes but may be tweaked by the phasing to avoid a green wave at higher speeds.
Cyclist need to either get out of the way of the 'sprint from the line' (an early green, as sometimes seen for buses, would do this but I can't see it being understood or respected by drivers) or need to get away from the kerb unless they are turning left. This is how I ride large roundabouts, the lane is mine and I will get to 10-15mph as quickly as the cars around me. Unfortunately the blue paint encourages cyclists to go straight on from the left hand kerb.
