From: Mortimer on
"Ian Jackson" <ianREMOVETHISjackson(a)g3ohx.demon.co.uk> wrote in message
news:GhZ9yDE0ld1LFwMD(a)g3ohx.demon.co.uk...
> On these large intersections, I hate the way that the phasing of the
> lights forces you to 'ratchet' your way around the roundabout, from
> traffic light to traffic light. Once you actually get onto the roundabout,
> I would have thought that it would be more efficient if you were allowed
> proceed through two (or even more) sets of lights.

Agreed. On a normal roundabout, without lights, you get used to the rule
that you wait to join the roundabout, but once you're on it you have
priority over everyone else who is waiting to join and do not need to stop
for anyone (unless it's to avoid an accident because someone else has
disobeyed the rulews of priority!). So on a roundabout with lights it's a
very alien concept to have to give way to anyone else.

From: Ret. on
Ian Jackson wrote:
> In message <Ys2dnWruDNukIUjWnZ2dnUVZ8j-dnZ2d(a)brightview.co.uk>,
> Mortimer <me(a)privacy.net> writes
>> "ChelseaTractorMan" <mr.c.tractor(a)hotmail.co.uk> wrote in message
>> news:spcbt5lnro8c6cbjfkd9nikvvii7eucq8h(a)4ax.com...
>>> On Mon, 26 Apr 2010 16:07:35 +0100, JNugent
>>> <JN(a)noparticularplacetogo.com> wrote:
>>>
>>>> There just shouldn't be traffic lights at roundabouts.
>>>
>>> an admission of failure really! There's a tiny roundabout near
>>> Lakeside shopping centre, (Essex) with lights on all the (I think) 5
>>> entries, they seem permanently switched off, I suspect because the
>>> traffic flows better without them.
>>
>> There was a lot of disruption last year while the Hopgrove roundabout
>> near York (A64 goes from dual-carriageway to single-carriageway and
>> meets the northern ring road) was modified. One of the changes was to
>> put traffic lights on the roundabout.
>>
>> Throughput on the roundabout is worse than ever, with long queues on
>> the single and dual sections of the A64 and on the ring road, at peak
>> times.
>>
>> For some reason, the traffic lights are 24-hour, rather than peak
>> periods only. It is infuriating to have to wait at the roundabout for
>> ages until the lights change, when you are the only car around late
>> at night!
>>
>>
>> The Milton Interchange roundabout under the A34 near Didcot was
>> redesigned and traffic lights were put on it. They have dramatically
>> improved the throughput of the roundabout - especially at peak
>> periods when traffic used to queue for ages to get out of the Milton
>> Park business park onto the roundabout. However the phasing of the
>> lights is very poor: traffic coming from Milton Park faces two sets
>> of lights, very close together (one to enter the roundabout, one to
>> let traffic join from Didcot) and they are phased so when one set of
>> lights goes green, the next set turns red about five seconds later.
>> Often you get the lead car at the first lights doing a wheelspin
>> start to try to get through the second lights before it changes.
>
> On these large intersections, I hate the way that the phasing of the
> lights forces you to 'ratchet' your way around the roundabout, from
> traffic light to traffic light. Once you actually get onto the
> roundabout, I would have thought that it would be more efficient if
> you were allowed proceed through two (or even more) sets of lights.

It would make more sense to get rid of the roundabout and just have a
traffic light controlled crossroads! They seem to manage perfectly well
without roundabouts in the US.

Kev

From: Ret. on
JNugent wrote:
> John wrote:
>> Given that many roundabouts are now having traffic lights installed
>> at the approach roads - has anyone else nearly got caught out like
>> me when approaching a roundabout with a green light showing - only
>> to realise at the last moment that the green light is for a
>> pedestrian crossing just a few feet short of the roundabout?
>>
>> Made me think - should there be a 'different' green signal for Ped X
>> ings? To reduce confusion with a normal green for Go.
>>
>> Should there be a sensible min distance from roundabouts where there
>> should not be a Ped Xing? After all - one pedestrian can press the
>> button and jam the whole roundabout.
>
> There just shouldn't be traffic lights at roundabouts.

But the problem is that on many roundabouts today, the dominant traffic flow
across the roundabout simply prevents drivers on 'lesser' roads from getting
*onto* the roundabout - particularly at busy times.

Kev

From: JNugent on
Ret. wrote:
> Ian Jackson wrote:
>> In message <Ys2dnWruDNukIUjWnZ2dnUVZ8j-dnZ2d(a)brightview.co.uk>,
>> Mortimer <me(a)privacy.net> writes
>>> "ChelseaTractorMan" <mr.c.tractor(a)hotmail.co.uk> wrote in message
>>> news:spcbt5lnro8c6cbjfkd9nikvvii7eucq8h(a)4ax.com...
>>>> On Mon, 26 Apr 2010 16:07:35 +0100, JNugent
>>>> <JN(a)noparticularplacetogo.com> wrote:
>>>>
>>>>> There just shouldn't be traffic lights at roundabouts.
>>>>
>>>> an admission of failure really! There's a tiny roundabout near
>>>> Lakeside shopping centre, (Essex) with lights on all the (I think) 5
>>>> entries, they seem permanently switched off, I suspect because the
>>>> traffic flows better without them.
>>>
>>> There was a lot of disruption last year while the Hopgrove roundabout
>>> near York (A64 goes from dual-carriageway to single-carriageway and
>>> meets the northern ring road) was modified. One of the changes was to
>>> put traffic lights on the roundabout.
>>>
>>> Throughput on the roundabout is worse than ever, with long queues on
>>> the single and dual sections of the A64 and on the ring road, at peak
>>> times.
>>>
>>> For some reason, the traffic lights are 24-hour, rather than peak
>>> periods only. It is infuriating to have to wait at the roundabout for
>>> ages until the lights change, when you are the only car around late
>>> at night!
>>>
>>>
>>> The Milton Interchange roundabout under the A34 near Didcot was
>>> redesigned and traffic lights were put on it. They have dramatically
>>> improved the throughput of the roundabout - especially at peak
>>> periods when traffic used to queue for ages to get out of the Milton
>>> Park business park onto the roundabout. However the phasing of the
>>> lights is very poor: traffic coming from Milton Park faces two sets
>>> of lights, very close together (one to enter the roundabout, one to
>>> let traffic join from Didcot) and they are phased so when one set of
>>> lights goes green, the next set turns red about five seconds later.
>>> Often you get the lead car at the first lights doing a wheelspin
>>> start to try to get through the second lights before it changes.
>>
>> On these large intersections, I hate the way that the phasing of the
>> lights forces you to 'ratchet' your way around the roundabout, from
>> traffic light to traffic light. Once you actually get onto the
>> roundabout, I would have thought that it would be more efficient if
>> you were allowed proceed through two (or even more) sets of lights.
>
> It would make more sense to get rid of the roundabout and just have a
> traffic light controlled crossroads! They seem to manage perfectly well
> without roundabouts in the US.

For certain values of "perfectly well"; with a set of traffic lights at
almost every *single* intersection on the grid-iron of Manhattan, progress is
painfully slow, whether by vehicle or on foot.

The whole idea of a roundabout is to keep traffic moving without unnecessary
delays. Using lights on the carriageway of a roundabout is absolutely crazy
since it prevents the natural function of the gyratory system by herding the
traffic together which reduces the space necessary for the essential
lane-changing.

*If* there is a pre-empting flow of traffic from one or more directions into
the roundabout, that could be balanced by a free-standing set of lights
controlling the flow into the roundabout from those directions only, rather
like the "ramp-metering" now used on some motorway slip-roads.

From: JNugent on
Ret. wrote:
> JNugent wrote:
>> John wrote:
>>> Given that many roundabouts are now having traffic lights installed
>>> at the approach roads - has anyone else nearly got caught out like
>>> me when approaching a roundabout with a green light showing - only
>>> to realise at the last moment that the green light is for a
>>> pedestrian crossing just a few feet short of the roundabout?
>>>
>>> Made me think - should there be a 'different' green signal for Ped X
>>> ings? To reduce confusion with a normal green for Go.
>>>
>>> Should there be a sensible min distance from roundabouts where there
>>> should not be a Ped Xing? After all - one pedestrian can press the
>>> button and jam the whole roundabout.
>>
>> There just shouldn't be traffic lights at roundabouts.
>
> But the problem is that on many roundabouts today, the dominant traffic
> flow across the roundabout simply prevents drivers on 'lesser' roads
> from getting *onto* the roundabout - particularly at busy times.

See the adjacent post. There are better ways of solving that.
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