Diverging Diamonds

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exiled
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Diverging Diamonds

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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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Re: Diverging Diamonds

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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.
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.
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Re: Diverging Diamonds

Post by Burns »

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.
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Re: Diverging Diamonds

Post by Peter Freeman »

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.
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Re: Diverging Diamonds

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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.
I thought a diverging diamond was a GSJ?
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Re: Diverging Diamonds

Post by Peter Freeman »

Oops - I meant not a FREEFLOW gsj.
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Re: Diverging Diamonds

Post by Mark Hewitt »

roadtester wrote:
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.
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.
Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?
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Re: Diverging Diamonds

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Mark Hewitt wrote: Sun Aug 12, 2018 09:19
roadtester wrote:
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.
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.
Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?
And I suppose that in turn can be turned into a dumb-bell so it can be single bridge.

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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Re: Diverging Diamonds

Post by Mark Hewitt »

roadtester wrote:
Mark Hewitt wrote: Sun Aug 12, 2018 09:19
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.
Yes doesn’t the GSJ roundabout not provide the same advantages with the disadvantage of requiring two bridges?
And I suppose that in turn can be turned into a dumb-bell so it can be single bridge.

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?
Yes the other but I was going to write. The bridge will be wider. But this may be offset by the approach roads etc.
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Re: Diverging Diamonds

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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
I think the name "dogbone" has been suggested for those. There's one near Holyhead:

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.
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Re: Diverging Diamonds

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wrinkly wrote: Sun Aug 12, 2018 14:31
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
I think the name "dogbone" has been suggested for those. There's one near Holyhead:

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.
Thanks - interesting. I was wondering if there were any others but drew a blank.

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

Post by wrinkly »

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.
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Re: Diverging Diamonds

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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.
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.
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Re: Diverging Diamonds

Post by Mark Hewitt »

roadtester wrote:
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.
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.
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

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Mark Hewitt wrote: Sun Aug 12, 2018 15:56
roadtester wrote:
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.
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.
Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?
Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?
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Re: Diverging Diamonds

Post by Johnathan404 »

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.
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Re: Diverging Diamonds

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roadtester wrote:
Mark Hewitt wrote: Sun Aug 12, 2018 15:56
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.
Bigger land take on the bone ends plus the bridge or underpass is wider than a roundabouts individual bridges?
Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?
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.
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Re: Diverging Diamonds

Post by roadtester »

Mark Hewitt wrote: Sun Aug 12, 2018 16:02
roadtester wrote:
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?
Not sure about the land take but yes, I'm guessing the underpass/bridge needs to be much wider - much like the diverging diamond?
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.
Much like the Catthorpe boneabout.
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Re: Diverging Diamonds

Post by Fenlander »

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

Post by Peter Freeman »

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?
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.
Last edited by Peter Freeman on Mon Aug 13, 2018 00:49, edited 1 time in total.
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