So you’ll of course know that this week TFL have released a video of how they plan to make Bow roundabout safe for cyclists.
The problem is, as you can see in the video but which isn’t mentioned in the accompanying text, all that’s changed is that cyclists now have a red light to stop them entering the ASL when the motor traffic has a green light. And when cyclists do have a green light to enter the ASL, they have a red light to proceed through the roundabout, meaning that cyclists will always meet a red light at this junction, either the ASL entry light or the main roundabout light.
Apparently this is:
"A cycle ‘early-start’ phase at the traffic signals on the eastbound and westbound entrance to the Bow roundabout. This would provide a dedicated green light phase to allow cyclists to travel ahead of other traffic"
Although it looks to me more like a “early-start-into-the-ASL-then-wait-like-nothings-changed” phase combined with a “sorry-your-too-late-now-wait-til-everyone-else-goes-first” phase.
I have a better solution, taken from looking at how the Dutch deal with such a junction, although my solution may require a few more curbs to be moved and a few more braincells to be engaged by TFL.
(grey is roadway, green is bikeway, blue is footway, and dark grey is impassible curb)
In Holland, they have 3 types of roundabout, and only 3, they’ve systematically removed all other types implementing sustainable safety. The largest and more complex of these is the signalised turbo-roundabout and it’s used on large multi-carriageway intersections to provide a high throughput of traffic.
The turbo-roundabout differs from a standard multi-lane roundabout by introducing a forced spiralling of traffic lanes and no lane changing while on the roundabout. Drivers pick their destination before entering by moving into a specific lane that then spirals through the roundabout to the destination exit. The large signalised variant of this adds traffic signals to control traffic flow in a similar way to signalised large standard roundabouts but have the advantage of allowing simultaneous left and right turns for certain directions.
If you take the existing Bow roundabout setup and adjust it to allow these simultaneous traffic flows, you end up with something that looks very much like a Dutch signalised turbo-roundabout.
Here’s how the light phases work out (via the medium of me scribbling all over the place with red and green pen).
Straight on motor traffic should be using the flyover or underpass and not entering the intersection and as such is not prioritised.
Each phase allows a single direction to turn right while the opposite directions can turn left. The routes within each phase can easily be adjusted based on whether there is any traffic coming via detection loops for motor vehicles and bicycles, and push buttons for pedestrians.
The north/south bicycle and pedestrian crossings are not given a direct single phase crossing due to the lower priority to these routes.
Now I’m just a guy thinking about how large junctions can be improved for cyclists and pedestrians in London, so there may be something obvious I’ve missed, but as far as I can see, this sort of configuration and phasing of lights could easily be introduced with just some alterations to curbs and how the traffic lights work.
Come on TFL, I see your half-arsed sticking plaster solutions that inconveniences cyclists causing them to ignore the new infrastructure, a raise you a practical tried and tested solution that works for all modes of traffic passing through the intersection.