Diverging Diamonds

The study of British and Irish roads - their construction, numbering, history, mapping, past and future official roads proposals and general roads musings.

There is a separate forum for Street Furniture (traffic lights, street lights, road signs etc).

Registered users get access to other forums including discussions about other forms of transport, driving, fantasy roads and wishlists, and roads quizzes.

Moderator: Site Management Team

Post Reply
User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Wed Feb 26, 2020 11:34

Chris5156 wrote:
Wed Feb 26, 2020 11:19
Peter Freeman wrote:
Tue Feb 25, 2020 03:37
Most USA DDI's have been conversions from standard signalised diamonds, but I've just seen (what I think is) the first cloverleaf converted to a DDI. It is on the I70 in Pennsylvania. This is interesting because -

(a) it's changed from fully-free-flow on both crossing roads to non-free-flow on one of them, but has been deemed to work better anyway;

(b) cloverleaf replacements, or modifications, generally require new structures.
Really interesting. Even though no structure renewals are needed, it looks rather gold-plated to me, in that all four of the new junction's sliproads are being built from scratch, when a little bit of adjustment to curves would allow the original junction's right-turn slips to be retained. I don't know why you'd tear up a length of existing road to build a new length of the same standard right alongside it.
America obviously employs the same wasteful design mindsets that we do.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Wed Feb 26, 2020 23:13

Chris5156 wrote:
Wed Feb 26, 2020 11:19
all four of the new junction's sliproads are being built from scratch, when a little bit of adjustment to curves would allow the original junction's right-turn slips to be retained. I don't know why you'd tear up a length of existing road to build a new length of the same standard right alongside it.
That struck me too when I first saw the layout drawing - I also am thrifty! Parts of all four ramps could have been retained, though obviously not their parts close to SR19. It's notable that the new layout has, beneficially, kept the crossovers decently far from both of SR19's existing nearby signalised cross-roads. It's also probably relevant that this interchange modification is actually part of a major project that effectively re-builds a significant length of I70, including all its ramp merges here. Ramp re-builds = small beer?

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Mon May 04, 2020 09:31

Peter Freeman wrote:
Mon Aug 13, 2018 00:45
Mark Hewitt wrote:
Sun Aug 12, 2018 16:02
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.
Most in the USA, so far, have been re-works of existing close diamonds, with well-documented benefits from a no-new-structures-required budget. However, the USA has an increasing number of new-built DDI's, and Australia's first DDI, currently under construction, is a new-build.
Of AU's first four DDI's, complete or in-planning -

#1 is a new build, totally replacing a hybrid parclo
#2 is a reconfiguration of an existing close diamond (no new structures)
#3 is a new build, totally replacing a 2-bridge roundabout
#4 is a reconfiguration of an existing close diamond (no new structures)
(added by edit in 2020 September):
#5 is a conversion from an existing half-diamond.
Last edited by Peter Freeman on Thu Sep 24, 2020 22:25, edited 1 time in total.

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Tue Jun 02, 2020 15:28

Second DDI for Australia goes to tender this year. Some info here -
https://www.tmr.qld.gov.au/Projects/Nam ... ge-upgrade

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Thu Sep 24, 2020 14:16

AU's fifth DDI has been announced, for Watson Street, Wallan, Victoria, interchanging with the M31 Hume Freeway. It will add a second over-bridge to convert a half diamond (north-facing ramps only) into a full diverging diamond. Design, construction timing and cost not yet revealed.

Further updates on DDI's in AU: I will post in the International Roads forum.

User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Mon Nov 30, 2020 18:10

The Netherlands is going all in with a six ramp parclo DDI/SPUI hybrid no idea what you call it.

https://www.openstreetmap.org/#map=16/52.1652/4.4564
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

User avatar
Truvelo
Member
Posts: 16656
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: Diverging Diamonds

Post by Truvelo » Mon Nov 30, 2020 23:38

Bryn666 wrote:
Mon Nov 30, 2020 18:10
The Netherlands is going all in with a six ramp parclo DDI/SPUI hybrid no idea what you call it.

https://www.openstreetmap.org/#map=16/52.1652/4.4564
I'm a bit confused by this because the proposed slip roads aren't compatible with the DDI. I then looked at the project website and it shows the junction with just the proposed slips and not the DDI. It's a shame Chris Zwolle doesn't post on here any more as he is likely to know the answer.

Edit - I've been on the Dutch forum and it appears the DDI is temporary. The issue of cyclists seems to crop up which the DDI in question has no facilities for.

Wait a minute what am I reading now?
Temporary traffic situation Leiden-West
The connection of the A44 to the N206 at Leiden-West will be redesigned. During the work, temporary use is made of a 'braided diamond connection'. Traffic drives on the left side of the road for a while. Traffic lights, line marking, traffic signs and screens between the lanes guide traffic safely over this temporary connection. Cyclists and pedestrians will be diverted via Plesmanlaan, Einsteinlaan and Robert Boyleweg.

So there will be a temporary diverging diamond, genius.


That is indeed the very concept of a DDI as it is also used in the United States. That you only have to wait for one traffic light when turning left onto the highway.

I also think that the added value in the Netherlands is limited if cyclists also have to cross the ground floor.

The original idea behind the American implementation was also that this would have very low costs: the existing artworks would be used and only the intersection planes would be rearranged, and thus the direction of travel would be flipped for a short time. In practice, quite a lot of DDIs are installed where the artworks are replaced, but they are also used in completely new situations. In the Netherlands you should then actually or not have cyclists or cyclists at a different level. And then the scope is a lot more limited I think.
How would you like your grade separations, Sir?
Big and complex.

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Tue Dec 01, 2020 01:04

This is a confusing situation! I saw from G.E. that the DDI was implemented very recently: in late-2018/early-2019. It replaced a former parclo/diamond hybrid layout. Those old arrangements are clearly visible on the GE image - ie. they haven't been ripped up. From the OpenStreetMap the works currently underway seemed, to me, to possibly be about connections to a new tunnel (under construction) that lies a little way to the south.

Having read the second (Truvelo) post, and then its edit, I'm just as confused. It seems to imply simply a dissatisfaction with the DDI, connected with cyclist provision (this is the Netherlands after all). This dissatisfaction despite the fact that all my USA observations (on-site at many DDI's) convince me that cyclist provision is no problem for DDI's - in fact, simpler than for a standard diamond.

I wonder what the final plan here actually is. Link to project website please.

Edit: on re-reading, the DDI was only ever a temporary layout, pending completion of the current project ...?!

User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Tue Dec 01, 2020 13:41

Peter Freeman wrote:
Tue Dec 01, 2020 01:04
This is a confusing situation! I saw from G.E. that the DDI was implemented very recently: in late-2018/early-2019. It replaced a former parclo/diamond hybrid layout. Those old arrangements are clearly visible on the GE image - ie. they haven't been ripped up. From the OpenStreetMap the works currently underway seemed, to me, to possibly be about connections to a new tunnel (under construction) that lies a little way to the south.

Having read the second (Truvelo) post, and then its edit, I'm just as confused. It seems to imply simply a dissatisfaction with the DDI, connected with cyclist provision (this is the Netherlands after all). This dissatisfaction despite the fact that all my USA observations (on-site at many DDI's) convince me that cyclist provision is no problem for DDI's - in fact, simpler than for a standard diamond.

I wonder what the final plan here actually is. Link to project website please.

Edit: on re-reading, the DDI was only ever a temporary layout, pending completion of the current project ...?!
I too have done some digging and it looks like the final arrangement will be a typical Dutch six ramp parclo, the DDI is a temporary roadworks layout.

No idea why Dutch cycle advocates - I've had a debate on Twitter with one historically - hate DDIs, they always cite conflicts as the reason but the DDI is more efficient and safer for cyclists than a standard diamond as you can run it with traffic so cyclists aren't held at every slip road either. I suspect there's this belief that "anything that also helps drivers is evil" at play.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Sat Apr 03, 2021 12:01

Peter Freeman wrote:
Tue Jun 02, 2020 15:28
Second DDI for Australia goes to tender this year. Some info here -
https://www.tmr.qld.gov.au/Projects/Nam ... ge-upgrade
Detailed design now released, and construction has begun. Cycle provision is down the centre of the reversal section, but pedestrians on the south side. Many USA examples take cycles AND pedestrians down the centre, of which I don't approve - my experience is that cycles and pedestrians don't mix well. Traffic islands are paved terra-cotta, as often in USA.
https://www.tmr.qld.gov.au/_/media/proj ... 270121.jpg

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Mon May 24, 2021 14:32

Peter Freeman wrote:
Sat Mar 23, 2019 13:14
Construction of Australia's first DDI is well underway. Here's a fly-through video simulation.

https://www.youtube.com/watch?v=X0MZAPc ... e=youtu.be
This project is now complete, except for final tidying up of landscaping. Google Earth has not yet caught up. Time for my site inspection I think, with AU's internal travel back to normal. :driving:

User avatar
ChrisH
Member
Posts: 3887
Joined: Wed Nov 13, 2002 11:29

Re: Diverging Diamonds

Post by ChrisH » Mon May 24, 2021 14:50

Peter Freeman wrote:
Mon May 24, 2021 14:32
Peter Freeman wrote:
Sat Mar 23, 2019 13:14
Construction of Australia's first DDI is well underway. Here's a fly-through video simulation.

https://www.youtube.com/watch?v=X0MZAPc ... e=youtu.be
This project is now complete, except for final tidying up of landscaping. Google Earth has not yet caught up. Time for my site inspection I think, with AU's internal travel back to normal. :driving:
Looks very nice from the video - although cycle lanes across the DDI look a bit dicey. I also liked the muzak on the video :mrgreen:

User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Mon May 24, 2021 16:43

ChrisH wrote:
Mon May 24, 2021 14:50
Peter Freeman wrote:
Mon May 24, 2021 14:32
Peter Freeman wrote:
Sat Mar 23, 2019 13:14
Construction of Australia's first DDI is well underway. Here's a fly-through video simulation.

https://www.youtube.com/watch?v=X0MZAPc ... e=youtu.be
This project is now complete, except for final tidying up of landscaping. Google Earth has not yet caught up. Time for my site inspection I think, with AU's internal travel back to normal. :driving:
Looks very nice from the video - although cycle lanes across the DDI look a bit dicey. I also liked the muzak on the video :mrgreen:
Yes, the whole point of a DDI is you can separate out the cycle movements to remove conflicts, but this particular example has retained the conflicts. I don't see an issue with having signal controlled crossings on the left turns activated by approaching cyclists - it would not affect capacity any more than a standard demand activated pedestrian crossing would.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Tue May 25, 2021 00:09

ChrisH wrote:
Mon May 24, 2021 14:50
Peter Freeman wrote:
Mon May 24, 2021 14:32

This project is now complete, ...
... although cycle lanes across the DDI look a bit dicey ...
In AU's second implementation and often in the USA, cyclists and/or pedestrians are segregated, sometimes by going down the middle of the reversal section, protected by concrete barriers. In this one they're not segregated, but there are marked and coloured cycle lanes on-road, as for many freeway interchanges - innovative designs or not. "A bit dicey" ? Well, yes, a bit - I find all on-road cycling rather dicey. I personally choose to cycle on footpaths instead of taking chances with road traffic, even though that's technically illegal. The footpath could be taken at this DDI, and probably will be. Note that this location will have few pedestrians and cyclists.
Bryn666 wrote:
Mon May 24, 2021 16:43
Yes, the whole point of a DDI is you can separate out the cycle movements to remove conflicts, but this particular example has retained the conflicts. I don't see an issue with having signal controlled crossings on the left turns activated by approaching cyclists - it would not affect capacity any more than a standard demand activated pedestrian crossing would.
The whole point of a DDI is that it's a better design for road vehicles than a standard diamond. Cycling, as with all freeway interchanges, is a relevant but subsidiary matter. "to remove conflicts" - what conflicts? Cyclists are controlled by the same signals as road vehicles, with the same signal sequence.

User avatar
jervi
Member
Posts: 1306
Joined: Thu Aug 17, 2017 16:29
Location: Lincoln / Haywards Heath

Re: Diverging Diamonds

Post by jervi » Fri Aug 27, 2021 13:21

Road Guy Rob has made a video on DDIs

User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Sat Oct 23, 2021 23:59

Turns out one has been at least considered for implementing in the UK after all.

WSP did a study in 2018 listing options for upgrading M6 J23 to operate for 2033 traffic and the DDI option, along with a 3 level roundabout... FFS, were seen to offer the highest capacity gains for the design year. Apparently the DDI has so much capacity it would still only be at 68% in 2033. It also advised that the NMU benefits are considerable due to walk with traffic stages and fewer conflict points.

Why are we not building these already?
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

User avatar
ravenbluemoon
Assistant Site Manager
Posts: 2209
Joined: Thu Oct 18, 2007 11:32
Location: Between Mansfield and Göteborg

Re: Diverging Diamonds

Post by ravenbluemoon » Sun Oct 24, 2021 00:43

WSP being innovative? :shock: (Sorry, I'm still bitter and holding a grudge after 4 years :lol: )

Denmark are also in the DDI game, having recently rebuilt an interchange on the E20 at Odense. GMaps Link

Didn't get to play on it on my last drive through as it was around midnight, and I had just had fun and games driving into central Copenhagen looking for a Covid test centre (on a Friday night to boot!). Loads of Sabristic stuff along that motorway, including the Great Belt bridge and the Oresund Crossing.
Tony/Alice (they,them)
~~~~~
Owner of a classic rust heap a.k.a. money pit, and other unremarkable older vehicles.
Usually found with a head in an old map or road atlas.

Did you know there's more to SABRE than just the Forums?
Add your roads knowledge to the SABRE Wiki today!
Have you browsed SABRE Maps recently? Try getting involved!


Peter Freeman
Member
Posts: 780
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: Diverging Diamonds

Post by Peter Freeman » Sun Oct 24, 2021 03:47

^ Denmark E20. Converted from a standard diamond about three years ago.

User avatar
Bryn666
Member
Posts: 31895
Joined: Thu Jun 20, 2002 20:54

Re: Diverging Diamonds

Post by Bryn666 » Sun Oct 24, 2021 10:29

ravenbluemoon wrote:
Sun Oct 24, 2021 00:43
WSP being innovative? :shock: (Sorry, I'm still bitter and holding a grudge after 4 years :lol: )

Denmark are also in the DDI game, having recently rebuilt an interchange on the E20 at Odense. GMaps Link

Didn't get to play on it on my last drive through as it was around midnight, and I had just had fun and games driving into central Copenhagen looking for a Covid test centre (on a Friday night to boot!). Loads of Sabristic stuff along that motorway, including the Great Belt bridge and the Oresund Crossing.
Don't worry it threw me as well! WSP aren't known for innovation :D
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

User avatar
Chris5156
Member
Posts: 14963
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: Diverging Diamonds

Post by Chris5156 » Sun Oct 24, 2021 12:07

Bryn666 wrote:
Sun Oct 24, 2021 10:29
ravenbluemoon wrote:
Sun Oct 24, 2021 00:43
WSP being innovative? :shock: (Sorry, I'm still bitter and holding a grudge after 4 years :lol: )

Denmark are also in the DDI game, having recently rebuilt an interchange on the E20 at Odense. GMaps Link

Didn't get to play on it on my last drive through as it was around midnight, and I had just had fun and games driving into central Copenhagen looking for a Covid test centre (on a Friday night to boot!). Loads of Sabristic stuff along that motorway, including the Great Belt bridge and the Oresund Crossing.
Don't worry it threw me as well! WSP aren't known for innovation :D
No, but then look at what we’re calling innovation - a proven junction design that has been in use in other countries for decades. As innovation goes it’s about on a par with copying someone else’s homework.

Post Reply