Diverging Diamonds
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Diverging Diamonds
Several of the YouTube channels I follow have started videos on diverging diamond interchanges in the US. What I was going to ask our experts is if they think this is something that could work here? Two of them seem to be quite enthused by them as a traffic management tool.
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- roadtester
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Re: Diverging Diamonds
Give them another ten years and they'll go back to the drawing board to refine it and they'll come up with the roundabout.exiled wrote: ↑Sat Aug 11, 2018 18:19 Several of the YouTube channels I follow have started videos on diverging diamond interchanges in the US. What I was going to ask our experts is if they think this is something that could work here? Two of them seem to be quite enthused by them as a traffic management tool.
Electrophorus Electricus
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Re: Diverging Diamonds
Even getting standard diamonds built here seems to be a challenge with the current trend being cheap, compact GSJs with curved sliproads and uriney* wee merges that mean you can't join the dual carriageway at a suitable speed.
*the original word I used fell foul of the language filter.
*the original word I used fell foul of the language filter.
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Re: Diverging Diamonds
We have some discussion already of DDI's (try a Sabre search), and there's a USA web site devoted to the concept. It's my favourite non-freeflow GSJ type. I've studied them on the ground in their USA home (Missouri/Kansas), and I can assure you they do work brilliantly.
Last edited by Peter Freeman on Mon Aug 13, 2018 00:26, edited 1 time in total.
Re: Diverging Diamonds
I thought a diverging diamond was a GSJ?Peter Freeman wrote: ↑Sat Aug 11, 2018 23:58 We have some discussion already of DDI's (try a Sabre search), and there's a USA web site devoted to the concept. It's my favourite non-GSJ intersection type.
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- Mark Hewitt
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Re: Diverging Diamonds
Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?roadtester wrote:Give them another ten years and they'll go back to the drawing board to refine it and they'll come up with the roundabout.exiled wrote: ↑Sat Aug 11, 2018 18:19 Several of the YouTube channels I follow have started videos on diverging diamond interchanges in the US. What I was going to ask our experts is if they think this is something that could work here? Two of them seem to be quite enthused by them as a traffic management tool.
- roadtester
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Re: Diverging Diamonds
And I suppose that in turn can be turned into a dumb-bell so it can be single bridge.Mark Hewitt wrote: ↑Sun Aug 12, 2018 09:19Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?roadtester wrote:Give them another ten years and they'll go back to the drawing board to refine it and they'll come up with the roundabout.exiled wrote: ↑Sat Aug 11, 2018 18:19 Several of the YouTube channels I follow have started videos on diverging diamond interchanges in the US. What I was going to ask our experts is if they think this is something that could work here? Two of them seem to be quite enthused by them as a traffic management tool.
The old Catthorpe had a sort of dumb-bell that had effectively been turned into what was topologically a roundabout, even if it was bone-shaped rather than circular, if you see what I mean - that also only requires one bridge (or one under-pass in the case of Catthorpe).
Can be seen here in this video about 30 seconds in:
https://www.youtube.com/watch?v=G_1_FwbTGbo
Also, unless I'm missing something, although the diverging diamond is a single-bridge layout, isn't it probably going to end up being a wider bridge?
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- Mark Hewitt
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Re: Diverging Diamonds
Yes the other but I was going to write. The bridge will be wider. But this may be offset by the approach roads etc.roadtester wrote:And I suppose that in turn can be turned into a dumb-bell so it can be single bridge.Mark Hewitt wrote: ↑Sun Aug 12, 2018 09:19Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?roadtester wrote: Give them another ten years and they'll go back to the drawing board to refine it and they'll come up with the roundabout.
The old Catthorpe had a sort of dumb-bell that had effectively been turned into what was topologically a roundabout, even if it was bone-shaped rather than circular, if you see what I mean - that also only requires one bridge (or one under-pass in the case of Catthorpe).
Can be seen here in this video about 30 seconds in:
https://www.youtube.com/watch?v=G_1_FwbTGbo
Also, unless I'm missing something, although the diverging diamond is a single-bridge layout, isn't it probably going to end up being a wider bridge?
Re: Diverging Diamonds
I think the name "dogbone" has been suggested for those. There's one near Holyhead:roadtester wrote: ↑Sun Aug 12, 2018 09:47 The old Catthorpe had a sort of dumb-bell that had effectively been turned into what was topologically a roundabout, even if it was bone-shaped rather than circular, if you see what I mean - that also only requires one bridge (or one under-pass in the case of Catthorpe).
Can be seen here in this video about 30 seconds in:
https://www.youtube.com/watch?v=G_1_FwbTGbo
ttps://www.google.co.uk/maps/@53.2963371,-4.62 ... a=!3m1!1e3
(that's actually one bridge though Google makes it look like two)
one at Rossett:
https://www.google.co.uk/maps/@53.10331 ... a=!3m1!1e3
and possibly others I've forgotten.
- roadtester
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Re: Diverging Diamonds
Thanks - interesting. I was wondering if there were any others but drew a blank.wrinkly wrote: ↑Sun Aug 12, 2018 14:31I think the name "dogbone" has been suggested for those. There's one near Holyhead:roadtester wrote: ↑Sun Aug 12, 2018 09:47 The old Catthorpe had a sort of dumb-bell that had effectively been turned into what was topologically a roundabout, even if it was bone-shaped rather than circular, if you see what I mean - that also only requires one bridge (or one under-pass in the case of Catthorpe).
Can be seen here in this video about 30 seconds in:
https://www.youtube.com/watch?v=G_1_FwbTGbo
ttps://www.google.co.uk/maps/@53.2963371,-4.62 ... a=!3m1!1e3
(that's actually one bridge though Google makes it look like two)
one at Rossett:
https://www.google.co.uk/maps/@53.10331 ... a=!3m1!1e3
and possibly others I've forgotten.
I think the Catthorpe one had been a dumb-bell and was later adapted - does anyone know if any of these have been designed on purpose like that from the beginning, or are they all modded dumb-bells?
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Re: Diverging Diamonds
The one at Holyhead has been a dogbone from the beginning (and originally had only a northward link road if I remember correctly).
The one at Rossett was originally a conventional dumbell if judged by its kerblines, but a dogbone if judged by its road markings.
The one at Rossett was originally a conventional dumbell if judged by its kerblines, but a dogbone if judged by its road markings.
- roadtester
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Re: Diverging Diamonds
Thanks again - interesting. On the face of it, given that the bone-like shape seems to offer the advantages of a roundabout GSJ combined with the need for only a single bridge like a diamond or a dumb-bell, it seems surprising that this layout isn't more common - or is there some really obvious drawback that I've missed?wrinkly wrote: ↑Sun Aug 12, 2018 15:11 The one at Holyhead has been a dogbone from the beginning (and originally had only a northward link road if I remember correctly).
The one at Rossett was originally a conventional dumbell if judged by its kerblines, but a dogbone if judged by its road markings.
I'm guessing the capacity of the bone-about is smaller than that of a big full roundabout and also has tighter radiuses on the bone-end bits which make it more awkward to negotiate.
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- Mark Hewitt
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Re: Diverging Diamonds
Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?roadtester wrote:Thanks again - interesting. On the face of it, given that the bone-like shape seems to offer the advantages of a roundabout GSJ combined with the need for only a single bridge like a diamond or a dumb-bell, it seems surprising that this layout isn't more common - or is there some really obvious drawback that I've missed?wrinkly wrote: ↑Sun Aug 12, 2018 15:11 The one at Holyhead has been a dogbone from the beginning (and originally had only a northward link road if I remember correctly).
The one at Rossett was originally a conventional dumbell if judged by its kerblines, but a dogbone if judged by its road markings.
I'm guessing the capacity of the bone-about is smaller than that of a big full roundabout and also has tighter radiuses on the bone-end bits which make it more awkward to negotiate.
- roadtester
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Re: Diverging Diamonds
Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?Mark Hewitt wrote: ↑Sun Aug 12, 2018 15:56Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?roadtester wrote:Thanks again - interesting. On the face of it, given that the bone-like shape seems to offer the advantages of a roundabout GSJ combined with the need for only a single bridge like a diamond or a dumb-bell, it seems surprising that this layout isn't more common - or is there some really obvious drawback that I've missed?wrinkly wrote: ↑Sun Aug 12, 2018 15:11 The one at Holyhead has been a dogbone from the beginning (and originally had only a northward link road if I remember correctly).
The one at Rossett was originally a conventional dumbell if judged by its kerblines, but a dogbone if judged by its road markings.
I'm guessing the capacity of the bone-about is smaller than that of a big full roundabout and also has tighter radiuses on the bone-end bits which make it more awkward to negotiate.
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- Johnathan404
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Re: Diverging Diamonds
The plan is to 'bone' ('teardrop'?) M3 J9 once the A34 has been removed from it.
As for divering diamonds, they would be excellent at many overloaded suburban roundabout interchanges. Sure there would be complaints that they are 'confusing', but it's not like people don't struggle to follow the lanes on a roundabout already.
As for divering diamonds, they would be excellent at many overloaded suburban roundabout interchanges. Sure there would be complaints that they are 'confusing', but it's not like people don't struggle to follow the lanes on a roundabout already.
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- Mark Hewitt
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Re: Diverging Diamonds
I think the thing with the diverging diamond is it isn’t built from scratch but a reworking of priorities using existing infrastructure. Which is reasonable.roadtester wrote:Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?Mark Hewitt wrote: ↑Sun Aug 12, 2018 15:56Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?roadtester wrote: Thanks again - interesting. On the face of it, given that the bone-like shape seems to offer the advantages of a roundabout GSJ combined with the need for only a single bridge like a diamond or a dumb-bell, it seems surprising that this layout isn't more common - or is there some really obvious drawback that I've missed?
I'm guessing the capacity of the bone-about is smaller than that of a big full roundabout and also has tighter radiuses on the bone-end bits which make it more awkward to negotiate.
- roadtester
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Re: Diverging Diamonds
Much like the Catthorpe boneabout.Mark Hewitt wrote: ↑Sun Aug 12, 2018 16:02I think the thing with the diverging diamond is it isn’t built from scratch but a reworking of priorities using existing infrastructure. Which is reasonable.roadtester wrote:Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?Mark Hewitt wrote: ↑Sun Aug 12, 2018 15:56
Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?
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Re: Diverging Diamonds
What would you describe Wisbech as having? One half is a normal roundabout linked to another but the other isn’t a normal roundabout but half a dog bone. Considering the sheer number of connections to it and the fact it feeds a dual carriageway through via a single lane and the dog bone end is traffic light controlled it does quite a good job.
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Re: Diverging Diamonds
Either a dumb-bell or a DDI can be single-bridge or two-bridge, and there is no reason why such bridges should be wider for one type than the other.roadtester wrote:
… And I suppose that in turn can be turned into a dumb-bell so it can be single bridge ...
Also, unless I'm missing something, although the diverging diamond is a single-bridge layout, isn't it probably going to end up being a wider bridge?
Last edited by Peter Freeman on Mon Aug 13, 2018 00:49, edited 1 time in total.