First Diverging Diamond in the US Opened Today

[Tarkus]

As you may have heard, MODOT opened up the first Diverging Diamond Interchange (DDI) at I-44 and the Kansas Expressway (MO-13) in Springfield, MO.

It's a rather curious design that I have mixed feelings on.  MODOT has plans to build several more, and here in Oregon, ODOT wants to build one at the I-5/Fern Valley Rd interchange in Phoenix, OR. 

As such, I'm kind of interested as to what my fellow roadgeeks think about DDIs.

-Alex (Tarkus)

[Hellfighter]

Have to drive one to find out...

[J N Winkler]

I think DDIs have been unfairly denigrated, especially on MTR.  There is a lot of fear that the crossovers will lead to wrong-way travel, but I think this is misplaced and FHWA's Turner-Fairbanks Highway Research Center seems to agree with me.  DDIs allow designers to get some of the queue management benefits of a SPUI without having to replace an existing bridge crossing, with all the traffic management impacts that implies.

It remains to be seen how critical provision of positive guidance is to the proper operation of DDIs.  I-44/SR 13 will provide early experience, but MoDOT is confident enough in the basic design that it already has at least two other DDIs in the works (I-435/Front Street and one of the three jobs involved in the Page Avenue contract in this month's letting).

[agentsteel53]

if people can manage to not drive the wrong way down an off-ramp, they can handle the DDI.  Lots of big red DO NOT ENTER signs, and execution of drunk drivers, should solve the problem.

[Revive 755]

It remains to be seen how critical provision of positive guidance is to the proper operation of DDIs.  I-44/SR 13 will provide early experience, but MoDOT is confident enough in the basic design that it already has at least two other DDIs in the works (I-435/Front Street and one of the three jobs involved in the Page Avenue contract in this month's letting).

The DDI bundled with the Page Avenue interchange with I-270 is actually on I-270 at the Dorsett Road interchange.

There is a third DDI planned for the US 65/Chestnut interchange in Springfield, MO:
http://www.modot.org/springfield/major_projects/Greene/ChestnutExp65.html

And I still say the name should be changed to "Crossover Diamond Interchange" since it's more descriptive.

[Truvelo]

Another advantage over a conventional diamond which hasn't yet been mentioned is the ability to do a U turn from the freeway without passing any traffic lights. This could be useful in the event of ramp closures at nearby interchanges.

[Duke87]

Really, the greatest flaw with it is that it's strange and new, so drivers aren't used to it and may not handle it properly.

You build enough of them and people get used to it, that won't be a problem anymore.

[J N Winkler]

There is a third DDI planned for the US 65/Chestnut interchange in Springfield, MO:

http://www.modot.org/springfield/major_projects/Greene/ChestnutExp65.html

If that is MoDOT's third, then I have found a fourth.  Call number 801 in the July 24 letting is for another DDI in Springfield, at the US 60/National Avenue interchange.  This job provides guide signing on a more generous scale than the I-44/SR 13 DDI, with overhead lane assignment signs guiding traffic straight ahead (to stay on National Avenue) or down ramps to US 60.

[vdeane]

A diverging diamond is one of the alternatives for the I-590/Winton Road interchange.

[Hellfighter]

I believe this is the interchange in question...

http://www.youtube.com/watch?v=c4p-d-6EnOQ

[njroadhorse]

I believe this is the interchange in question...

http://www.youtube.com/watch?v=c4p-d-6EnOQ

That's freaking awesome 

[FreewayDan]

There are more Diverging Diamonds planned in other areas in the U.S.
http://en.wikipedia.org/wiki/Diverging_diamond_interchange

[US71]

I drove it and wasn't sure what to think. Maybe I'll go back after all the construction work is completed in 2-3 weeks.

As far as going the wrong way, the local NBC station reported it took less than an hour for someone to go the wrong way after the DDI opened. 

[Bryant5493]

It's not really too, too confusing. Everything is just reversed from regular, everyday U.S. driving.


Be well,

Bryant

[AZDude]

What a pain in the ass!

[Bickendan]

That is an interesting design.

[vdeane]

As far as going the wrong way, the local NBC station reported it took less than an hour for someone to go the wrong way after the DDI opened. 

The signage looks quite clear, though it would help if they could have finished the barriers before opening it up to traffic (the way they have it in the video, it looks like a temporary situation due to construction).  If that person can't follow signs they shouldn't be allowed to drive in the first place.

[Tarkus]

Hellfighter, thanks for sharing that video--it's cool to see it in its actual operating conditions.  I'm finding myself increasingly warming to the DDI.  I'd definitely be more comfortable with one of those than a dumbbell or raindrop interchange.

-Alex (Tarkus)

[NJRoadfan]

I'm surprised NJDOT hasn't graced us with one of these to confuse drivers even more.... heck we don't even have a real SPUI in this state yet.

[njroadhorse]

I'm surprised NJDOT hasn't graced us with one of these to confuse drivers even more.... heck we don't even have a real SPUI in this state yet.

Hehe and I know just where to put one too

[Mergingtraffic]

I'm surprised NJDOT hasn't graced us with one of these to confuse drivers even more.... heck we don't even have a real SPUI in this state yet.

Drive up to CT Exit 48 off the Merritt Parkway with CT Route 111.

[Alps]

I'm surprised NJDOT hasn't graced us with one of these to confuse drivers even more.... heck we don't even have a real SPUI in this state yet.

NJ 133 at NJ 33, coming soon.

[NJRoadfan]

The Penn's Neck US-1 bypass is supposed to have 2 as shown in the preferred alternative, who knows when thats getting built.

[Darkchylde]

A diverging diamond has been floated recently as a way to remodel the US 190/LA 22 interchange in Mandeville.

[BigMattFromTexas]

This looks cool, i want to go on this
BigMatt