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Thread: Roundabouts getting replaced by traffic lights into straight junctions?

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    Default Roundabouts getting replaced by traffic lights into straight junctions?


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    I wonder what is this Bracknell forest council obsession with roundabouts getting replaced by traffic lights into straight junctions?

    Is it not the case roundabouts are better? Why they are doing this and is this happening around you? I have the weird feeling there is council budget that needs to be spent on road works and they just do that to spent the money. Each year we happen to have some unneccessary road fix here.

    2008 Roundabout: https://www.google.com/maps/@51.3907...7i13312!8i6656

    2018 Traffic Light intersection:
    https://www.google.com/maps/@51.3908...7i16384!8i8192

    2016 Roundabout:
    https://www.google.com/maps/@51.4125...7i13312!8i6656

    Now we have awkward multilane traffic lights. Previously on rush hour times there was a queue that moves. Now the queue is much longer and is stop start.

    Studies by Kansas State University measured traffic flow at intersections before and after conversion to roundabouts. In each case, installing a roundabout led to a 20 percent reduction in delays. Additional studies by the IIHS of intersections in three states, including Washington, found that roundabouts contributed to an 89 percent reduction in delays and 56 percent reduction in vehicle stops.

    Why on Earth anybody will change roundabout to traffic light?

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by Val View Post
    Is it not the case roundabouts are better?
    No.

    Studies by Kansas State University measured traffic flow at intersections before and after conversion to roundabouts. In each case, installing a roundabout led to a 20 percent reduction in delays. Additional studies by the IIHS of intersections in three states, including Washington, found that roundabouts contributed to an 89 percent reduction in delays and 56 percent reduction in vehicle stops.
    What kind of junction was replaced? Do you know? What is a four-way stop? I'd guess that it probably was.

    What happens generally is that roundabouts flow more traffic more smoothly than a cross-roads operating under 'Give Way' rules, but they eventually reach a point where the flow of traffic along the route that has the biggest flow begins to impede crossing traffic.

    At this point, traffic lights are more efficient. The timing on the lights is usually 'intelligent' and can be altered according to traffic density or triggered by a waiting vehicle.

    Roundabouts are - AFAIK - also risky for cyclists once they get busy, with particular risks from left-turning vehicles, and when the cyclist is turning right. You can also build in pedestrian crossings when you have a traffic signal controlled junction, something that's not so easy with roundabouts.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Capacity, and uneven flow as Spin says. Also accident reduction, queue balancing, priority to certain movements, adding pedestrian facilities.

    I've designed several.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Remember this is Val, guys.

    He’s a bit of a dunce.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    I'd have agreed with Val - that r/b tend to be more efficient. I begrudgingly concede they may not be 'under certain circumstances'. There's a nightmare of a light-controlled cross-road in Devon that would really benefit from being made into a r/b but I do (now) see that if it was although the traffic would move better, it might give undue priority to travel in a certain direction, and that lights do at least make it more equal (even if the tailbacks it causes are often up to a mile in either main direction).

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    According to Birmingham City Council the modern road planning strategy is to make the roads unfriendly to private car transport to the point of "forcing car drivers onto public transport"*

    * Or in reality, private transport as there is no public transport any more.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Bear in mind also that Bracknell is home to TRL, and the roads there are probably more observed (and experimented with) than anywhere else in the UK.
    (I believe).

    This has something to do with researchers far preferring to be left alone in their cubbyholes and not liking to get out into the fresh air too much - so they tend to spend more time observing locally than far away from said offices.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    I immediately thought of the Coral Reef junction when I read the title and it turned out I was correct.

    I do agree with Val that the roundabout was a better solution the times that I have used that junction, but I've not used it during rush hour or other peak times.

    I'm not sure it's an 'obsession' though as it seems just the one roundabout.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by McNab View Post
    I immediately thought of the Coral Reef junction when I read the title and it turned out I was correct.

    I do agree with Val that the roundabout was a better solution the times that I have used that junction, but I've not used it during rush hour or other peak times.

    I'm not sure it's an 'obsession' though as it seems just the one roundabout.

    IIRC it wasn't traffic light controlled (or, it was, but not at all times), but the main issue was that it had a huge throughput of traffic in most directions so generated huge tailbacks. Not helped (I think) buy the large roundabout just north of (Sainsbury's) which is one of these odd ones that is more like a motorway junction, but totally traffic-light controlled.

    To be frank though - the main issue is that the A329 (IIRC) is just far too busy now. It needs to become a full-on 'urban motorway' with slip-road junctions for access into Bracknell and the surrounds, and let the through (M4 to M3) traffic flow freely. (imho)

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by RiceBurner View Post
    Bear in mind also that Bracknell is home to TRL, and the roads there are probably more observed (and experimented with) than anywhere else in the UK.
    (I believe).

    This has something to do with researchers far preferring to be left alone in their cubbyholes and not liking to get out into the fresh air too much - so they tend to spend more time observing locally than far away from said offices.
    versus 'Civil (sic) Servants make astronomical expenses claims as they drive all over the country to observe situations they could walk to...' headlines

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by GreenMachine View Post
    I'd have agreed with Val - that r/b tend to be more efficient. I begrudgingly concede they may not be 'under certain circumstances'. There's a nightmare of a light-controlled cross-road in Devon that would really benefit from being made into a r/b but I do (now) see that if it was although the traffic would move better, it might give undue priority to travel in a certain direction, and that lights do at least make it more equal (even if the tailbacks it causes are often up to a mile in either main direction).
    is that the one by a particular fish and chip shop? If so, the traffic coming from/going to Saunton needs a completely different route but someone won't want that

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by slowsider View Post
    versus 'Civil (sic) Servants make astronomical expenses claims as they drive all over the country to observe situations they could walk to...' headlines
    TRL was privatised several years ago.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Quote Originally Posted by GuzziPaul View Post
    TRL was privatised several years ago.
    Almost. It became TRL then, before it was TRRL , described as "the Department for Transport's boffin repository in the woods"

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    A decade or so ago "they" converted a lot of roundabouts to light-controlled roundabouts on the Bristol Ring Road. Problem was they didn't install lights on all the approaches, so some approaches got hugely congested at peak times. I *think* the idea was that the uncontrolled lanes would have an empty road between cycles, but with lorries taking longer to clear the junction after red, German car drivers gambling on amber and filtering bikes pulling away quickly on green, the road was never as empty as it should have been. And with the mid-roundabout lights not easily visible on approach, controlled traffic didn't usually have sufficient warning to leave a single-car gap to allow uncontrolled traffic to filter in.

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    Default Re: Roundabouts getting replaced by traffic lights into straight junctions?

    Amateurs!
    Start with a 5-way roundabout


    and improve it by making a traffic light controlled junction.

    In case anyone is wondering, there are 42 sets of lights.

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