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Robin[_4_] · February 15th 17, 01:09 PM posted to uk.transport.london

On 15/02/2017 13:50, d wrote:
On Wed, 15 Feb 2017 10:26:15 +0000
Neil Williams wrote:
On 2017-02-15 09:38:59 +0000, d said:

Putting traffic lights on roundabouts has always struck me as a ridiculous
thing to do. Its as if the traffic planners didn't quite understand the
purpose of a roundabout or how it worked and assumed it was no different
to a 4 way junction. Once you've added the lights the roundabout is now
completely redundant and you'd probably get better traffic flow if you did
replace it with a simple junction.

Roundabouts work very well where there is a reasonably balanced traffic
flow on all 4 (or more) arms. They fail badly where the traffic is
highly directional, e.g. towards a city centre.

Which is when a normal signalled junction should have been installed.

The way to prevent this is to place traffic lights on all but one of
the arms, having no lights on an arm that is not a "blocking" flow but
does have reasonable demand. In the example above, putting them on all
but arm C would allow continuous traffic flow, but would regulate arm B
such that those on arm C could get out and queueing is prevented.
This has an advantage over a traditional traffic light junction as
traffic is always flowing - when the lights are on amber or all on red

Or just have junctions with the american system of turn on red and at less
busy times simply have flashing orange on all approaches.

I'd like to see you implement that or any other of your designs at the
Redbridge roundabout:

,18z

(I would put negotiating it when the lights are out of action in the
same class as Sir Thomas Beecham's famous two.)

--
Robin
reply-to address is (intended to be) valid