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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?

    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?

    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?

    You would have thought roundabouts, or Islands, as they say in Leicester, 😂 would be better for traffic flow. Thatís why they put so many of them in Milton Keynes. And it seems to work.

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

    Quote Originally Posted by BikerJo View Post
    You would have thought roundabouts, or Islands, as they say in Leicester, �� would be better for traffic flow. That’s why they put so many of them in Milton Keynes. And it seems to work.
    Up to a point... then they clog up and actually slow the traffic flow down. Think about it - if there is a non-stop flow in one direction, it's almost impossible to find a gap to cross that flow.

    And Milton Keynes was designed for the car, and they planned ahead for increased traffic flow.

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