Diverging Diamond Interchanges

[brad2971]

Normally, one would have a chuckle at the thought of good, patriotic Missourians borrowing ideas from the French , but this latest traffic innovation:


http://www.modot.org/springfield/major_projects/Greene/I-44andRoute13.html

sounds like it has quite a bit of merit to it MoDOT is apparently redoing 4 interchanges using the Diverging Diamond method, and UDOT is reworking another interchange on I-15 this way, too.

Would suck to be a pedestrian crossing this interchange, though, as the pedestrian(s) would end up effectively waiting in the middle of the street to cross both ends of it

[74/171FAN]

Looks like an SPUI without everyone being affected by the stoplight

[njroadhorse]

I like this design.  It's still a simple SPUI (essentially) with crossing lanes that eliminate dangerous left turns across busy highways

[Ian]

that actually looks like a nice idea for an interchange!

[Chris]

The idea is interesting, but I'm afraid it's a bit too unorthodox to actually work. You have to drive in the "wrong" direction.

[akotchi]

Like any other new traffic pattern (such as roundabouts or SPUI's at one time), this would take a bit of getting used to.  I like it, though, in that the signal operations are simplified.  Conventional diamonds are terrible when left turn volumes to the ramps are high.

[ComputerGuy]

Ooh...

[Southern Illinois SKYWARN]

Hmm... That sounds rather clever, at least on paper.  However, it would take some getting used to, so MODOT may need to do some kind of massive publicity campaign.

[rawr apples]

Quite interesting. I like it, I like it when they try new things

[Scott5114]

The following was originally posted by me to an MTR thread about DDIs.

My take is that the SPUI should be used at high traffic volume
interchanges, especially where lots of left-turn traffic is expected.
Traditional diamonds are best for slower interchanges such as rural
locations, and interchanges where most of the traffic is right-turning
(so that the benefits of a SPUI would be negligible, and little
"corner-cut" ramps could be used instead.

The DDI seems to me to be a solution in search of a problem. Having
two "cross-over" locations is just asking for trouble...you're bound
to get Grandpa Artie all confused and driving into incoming traffic.
I'm not sure if the additional thought required of drivers is too much
for the safety improvement of not having to turn left. It is inferior
to the SPUI because it could still require waits at two signals,
whereas the SPUI requires only one (though left-turning traffic from
the ramps will only have to have one, they will have a yield to
contend with, which can potentially be as long of a wait as a
stoplight if traffic is heavy). About the only good thing about the
DDI is that it's cheaper than a SPUI.

[Alex]

Spoke with a couple of people at the Grand Prairie Parkway DDI today while photographing it on the drive from the Quad Cities to Omaha. They were doing some research on a recent accident involving a wrong way driver, which claimed the lives of two police officers. The accident occurred on I-80 just to the west of this DDI. While discussing the interchange, they asked what were some of the opinions drivers had of them, and I shared some of the opinions we road enthusiasts have of them. They asked if any of the confusion involving DDI's have resulted in either a major accident or a fatality. I cannot think of any off-hand, does anyone here know of any such incident?

[hbelkins]

A former member of this forum used to call them "death diamonds," but I have never heard of any issues with DDIs.

[theline]

Coincidentally, just this morning there was a serious wrong-way driver accident here in South Bend: http://www.wsbt.com/news/local/stretch-of-the-bypass-closed-after-wrongway-crash/38741088

The pertinence to this discussion is that there are no DDI interchanges in the area of the accident. Though her entrance point hasn't yet been reported, the most likely one is SR-23. a standard diamond. My point is that you don't need a DDI to have a wrong-way driver. It would be interesting to see a statistical comparison of DDI's vs. other interchange designs, regarding incidents of wrong-way driving.

[pianocello]

Wow, it's kinda cool to look back at the posts from when DDI's were just an idea on paper 7 years ago!

Re: wrong-way driving: I was under the impression that signage and road geometry at DDI's were usually such that head-on collisions are minimized. Unless something was done wrong, the crossover intersections should be at an angle wide enough that you would have to make a right turn to go the wrong way on the road. In my experience (however limited it may be), it just feels like the road splits into a pair of one-way streets for the duration of the interchange.

[tradephoric]

Unfortunately, the DDI craze has led to them being overbuilt across the country in locations where they weren't a good fit.   There are examples of DDI's replacing Parclos.  A simple Parclo could prevent the need for diverging movements along the arterial (leading to fewer conflict points) but engineers are enamored with the DDI.  But i think we are starting to get back to earth.  DOTs that have a lot of experience with them (UDOT) have admitted in their published DDI reports that they haven't performed as well as they had hoped.  This is the first line found in the Utah DDI guide.  I think it speaks for itself.     

As new innovations are introduced and applied, they sometimes struggle for initial acceptance but then gain in popularity until they are often over-applied.

[Alex]

Just drove through the new DDI to the west of US 77 on I-80 outside Lincoln. This one is replacing a parclo interchange with Nebraska L55K.
A full cloverleaf interchange between I-74/US 6 and IL 5 (John Deere Expressway) in Moline is under study to be converted to a DDI as well. Some of them are overkill while others seem to fall under the road diet category to me.

[Jmiles32]

Unfortunately, the DDI craze has led to them being overbuilt across the country in locations where they weren't a good fit.   There are examples of DDI's replacing Parclos.  A simple Parclo could prevent the need for diverging movements along the arterial (leading to fewer conflict points) but engineers are enamored with the DDI.  But i think we are starting to get back to earth.  DOTs that have a lot of experience with them (UDOT) have admitted in their published DDI reports that they haven't performed as well as they had hoped.  This is the first line found in the Utah DDI guide.  I think it speaks for itself.     

As new innovations are introduced and applied, they sometimes struggle for initial acceptance but then gain in popularity until they are often over-applied.

I agree DDIs can only handle so much traffic, just like all interchanges, and aren't always a good fit. For example Vdot will soon be constructing two DDIs on I-66, one at Exit 40 in Haymarket and one at Exit 62 in Vienna. I think the one in Haymarket is a great idea while the one in Vienna may be well overburdened and cause even more delays. In short even DDIs may not always be the best option

[tradephoric]

Here's a link to the I-74/US6/IL5 cloverleaf interchange in Moline that Alex referenced.  I don't hide the fact that i'm not a big fan of the DDI.  But to all the DDI proponents, do you really think this is right interchange to convert to a DDI?

https://www.google.com/maps/@41.4714764,-90.4945593,410m/data=!3m1!1e3

[Alex]

Here's a link to the I-74/US6/IL5 cloverleaf interchange in Moline that Alex referenced.  I don't hide the fact that i'm not a big fan of the DDI.  But to all the DDI proponents, do you really think this is right interchange to convert to a DDI?

https://www.google.com/maps/@41.4714764,-90.4945593,410m/data=!3m1!1e3

Considering recent upgrades to IL 5 just to the east to enhance it as an expressway, I do not think it is the right interchange here.

September 2015 story on the DDI: http://qctimes.com/news/local/changes-being-considered-for-i--john-deere-road-interchange/article_9fbde01d-c10c-5546-8020-7eb7a7e41c3b.html

[paulthemapguy]

Here's a link to the I-74/US6/IL5 cloverleaf interchange in Moline that Alex referenced.  I don't hide the fact that i'm not a big fan of the DDI.  But to all the DDI proponents, do you really think this is right interchange to convert to a DDI?

https://www.google.com/maps/@41.4714764,-90.4945593,410m/data=!3m1!1e3

Considering recent upgrades to IL 5 just to the east to enhance it as an expressway, I do not think it is the right interchange here.

September 2015 story on the DDI: http://qctimes.com/news/local/changes-being-considered-for-i--john-deere-road-interchange/article_9fbde01d-c10c-5546-8020-7eb7a7e41c3b.html

It looks like there's a trailer park just to the southeast called "cloverleaf village" in reference to the interchange.  Won't that be funny if it isn't a cloverleaf anymore!  Will they have to change their name? 

[NE2]

Will they have to change their name? 

No.

[jeffandnicole]

Here's a link to the I-74/US6/IL5 cloverleaf interchange in Moline that Alex referenced.  I don't hide the fact that i'm not a big fan of the DDI.  But to all the DDI proponents, do you really think this is right interchange to convert to a DDI?

https://www.google.com/maps/@41.4714764,-90.4945593,410m/data=!3m1!1e3

Considering recent upgrades to IL 5 just to the east to enhance it as an expressway, I do not think it is the right interchange here.

September 2015 story on the DDI: http://qctimes.com/news/local/changes-being-considered-for-i--john-deere-road-interchange/article_9fbde01d-c10c-5546-8020-7eb7a7e41c3b.html

It looks like there's a trailer park just to the southeast called "cloverleaf village" in reference to the interchange.  Won't that be funny if it isn't a cloverleaf anymore!  Will they have to change their name? 

This very thing has happened a lot in New Jersey, especially when a business opens up by a traffic circle and included 'Circle' in their name.  One recent example is Circle Liquors which sat at the former Somers Point Circle, which is now a regular + intersection.

Then again, NJ has a hard time giving up names as well.  The jungle at 30 & 130 is still known as the Airport Circle, even though the airport closed in the 1950's.  Just down the road, you can view NJDOT's self-named Collingswood Circle traffic camera...which overlooks a normal intersection.

[kphoger]

Scott5114 nailed it on the head years ago: the primary advantage of a DDI is that it's cheap. Does anyone really wonder why Missouri of all places has been such a pioneer of them? It's because Missouri hurts for highway network funds and is eager to try new, cheaper improvements.

Sorry we've now gotten off topic from the original necro-post-question.

[jakeroot]

Bit of a revival here...

In 2013, South Africa converted the diamond interchange at the N2's junction with the R102 north of Durban to a diverging diamond interchange. The interchange is known locally as the KwaMashu interchange. It was the first diverging diamond interchange constructed in a "keep-left" country, and also the first in the southern hemisphere.

http://www.civildesigner.com/press/kwamashu.pdf     ---     https://goo.gl/xAHrZI

https://youtu.be/b8jO0b4wXfk

[tradephoric]

A new DDI at University & I-75 in Michigan is signed for 25 mph.  Directly upstream and downstream of the DDI the arterial is signed for 45 mph.  Subdivision streets are signed for 25 mph.  Good thing drivers travel nearly 2500 feet through this suburban DDI at 25 mph.  Maybe the designers just want drivers to slow down so they can admire their fabulous DDI.  We are living in bubble-boy world where high speed suburban arterials are signed for 25 mph.