'diverging diamond' interchanges

[masraum]

There are a couple/few roundabouts in the Houston metro area. I've run into a couple with only one lane, but most seem to be multiple lanes. I've never noticed an issue with the multiple lane versions. There are folks that don't seem to understand them, but there are also folks that can barely navigate a 4-way stop.

I've also seen some with stop signs which boggles the mind.

[masraum]

How's this for round-a-bouts

[masraum]

Rome's got one too.

[wilnj]

Originally Posted by flatbutt

We call them "circles". They are disappearing along with jug handles.

Thank goodness. Let’s keep Taylor Ham and get rid of that other uniquely Jersey thing.


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[Superman]

The first of these to be built in Washington State was completed recently quite close to my house. It is indeed far more efficient than an ordinary freeway overpass. And while humans are thorough in proving that nothing can be made foolproof, it would be very difficult for someone to go the wrong way in a lane on that bridge. Substantial concrete barriers make that nearly impossible,

As I say, it is a very efficient bridge. There are only two light "modes" and when a mode is "on," the traffic with the green lights can enter and exit the bridge all at once regardless of whether they are getting on the bridge, getting off the bridge, or turning left to enter the freeway. In other words, wait times are quite short, you will see a maximum of ONE red light during the experience, and whatever backed up line of traffic is with you when the light turns green will be emptied before the light turns red again.

[stevej37]

^^^ The video in post#8 says the diverging diamond can handle twice as many cars as the old type.

And much safer.

The one near me, I first used it when it was built about 4 years back. I was surprised about the lanes switching sides, but all went smoothly.

[flatbutt]

Originally Posted by wilnj

Thank goodness. Let’s keep Taylor Ham and get rid of that other uniquely Jersey thing.


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That's rather a nebulous topic. We could start with getting rid of the law prohibiting pumping our own gas, but this is a topic for another thread.

[stevej37]

It can't be cheap to build these ddi's.....it took them close to a year to build one near me.

[stevej37]

There are two different variations of the 'Michigan left turn' here.
One is going straight thru the intersection..do a u-turn and make a right.
The other one is make a right at the intersection...do a u-turn and go straight thru the intersection.

Both work.

Here is the first one....



Here is the other type that is not as common in MI

[Superman]

Originally Posted by stevej37

It can't be cheap to build these ddi's.....it took them close to a year to build one near me.

I think public works are cool. In this instance, one of the complications which add....complications....to these projects is that traffic is crossing the bridge under construction. And in the case of many of diverging diamond bridges, they are nearly always over a freeway and incorporation onramps and offramps. The complications of accommodating two onramps and two offramps in addition to street lanes in both directions make them more...complicated.

It is like repairing a watch while the watch is ticking. If they could just close the bridge, the time investment would probably be cut roughly in half. But they almost never can do this. Simply closing a bridge would raise, not lower, total complications. City and county people would be involved, and would need to buy off. This is unlikely.

[Daves911L]

There is what I think is a derivative of this "double diamond" intersection (didn't know what it was called until now) a few miles west of me. Its not over a freeway, but at what was the intersection of two very busy 4-lane highways. It opened about a year ago, replacing a light-controlled intersection with left turn lanes. It took forever to build, and i assume was very expensive. It is very weird, and requires a very large chuck of real estate. It is confusing. There is a lot of striping and signage, but a bit like the back straight at sebring, just so much flat concrete you are not really sure which way is ahead. 1 long and irritating light was replaced by 3 shorter lights. It seems quicker going through now, but that may be perception more than reality, from breaking up the wait into 3 intervals. The opportunity for head-ons is real and on two occasions I have personally seen cars going the wrong way down the counter-intuitive "changeover" lanes.

I'm finding myself entertaining the notion that this and other bizarre traffic engineering I've seen in the past decade are actually intended to discourage private vehicle use, in favor of mass transit.

There are several local examples of the "traffic circle fetish" here. Where some community activist or local politician set about to get a traffic circle built just because it was the "cool" thing to do. Don't get me wrong, I think traffic circles work great. Negotiated them easily while driving in Europe for decades. But there is a right way, and a wrong way, to build them. They require good visibility both on approach and when in the circle, and an adequate radius. Many of our local traffic circles are built the "wrong" way and do more harm than good.

[stevej37]

^^^ diverging diamond interchange.

I found the ones here very easy to negotiate after the surprise of exchanging right for left and then back.

[hbueno]

Originally Posted by flatbutt

That's rather a nebulous topic. We could start with getting rid of the law prohibiting pumping our own gas, but this is a topic for another thread.

There are two things here in NJ that I prefer to keep. One is the pumping gas issue - I have no problem at all with the status quo, esoecially on cold or rainy days. The second is Bergen county blue laws. Having most businesses closed on Sundays gives us one day of peace and less traffic.

[Bob Kontak]

Originally Posted by stevej37

It can't be cheap to build these ddi's.....it took them close to a year to build one near me.

Sorry for going back to the roundabouts but this one, 300 yards from my shop, was probably three plus big ones. I'm betting closer to four million.

I see some scary/ignorant stuff on this circle BUT nothing high speed so it does save lives.

Very complex for the uninitiated.

[stevej37]

^^^ There was a similar one near me that was a 4-way stop intersection. It was almost always backed up with 5 or more cars on both sides of the busier road.
They changed it to a round-about and now I hardly ever see cars waiting....it flows smoothly.

[masraum]

Originally Posted by flatbutt

I've only ever seen the type C here. We used to have a bunch, but some have been replaced with wider roads and lights.

This is the best, they are all cambered and you can take all 4 as many times as you want.

[URY914]

There is a diverging diamond in Nassau county just north of Jax here in FL. It goes under I-95 where US1 intersects. If you're coming to Amelia Island for the concours or Werksfest you be driving thru it. It may be the first one in the state.

[Tervuren]

There is an intersection set I used to avoid even if it meant a longer route.
They redid things and put one of these things in.
Waaaaay better.

I didn't know the setup, but came through after some construction and was indeed surprised by the finding the road lines leading me to the wrong side of the road.

Originally Posted by stevej37

^^^ diverging diamond interchange.

I found the ones here very easy to negotiate after the surprise of exchanging right for left and then back.

[masraum]

It seems Texas has 6 active with 1 in the works. None of them are anywhere that I anticipate being.

https://divergingdiamond.com/loc/texas/

[rattlsnak]

Originally Posted by KC911

Oh my .... hope they don't come south... roundabouts are bad enough here . Polite southern drivers who slow way down (or stop) for others and have rarely been out of Mayberry are not a good mix with changing traffic interchanges !

Plenty of them in the ATL area already..!