'diverging diamond' interchanges
 

We've had a couple in Grand Rapids for about 5 years now. Strange traffic flow...but it works and is much safer. Eliminates the left turners waiting for oncoming traffic to clear.

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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 ;)!

I think they are easier to navigate than round-abouts.
If people just follow the arrows and lights, there should be no accidents due to making a hasty decision while turning left in front of traffic.

If people just follow the arrows and lights...

so we trade broadsides for head ons when someone runs a light?

There are just way too many cars on our roads.

Hate to tell you KC911 but it looks like this is coming south. Apparently we are to get one at the intersection of hwy 42 and I40. Plus 9 new roundabouts planned for the county. Your comments about drivers here are spot on. Real problem is NCDOT. They take forever to do a road project. They are in the 4th year of widening 5 miles of 2 lane to 4 lane. Constantly changing slalom course of orange and white barrels.

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We have them in Va. and they work. Its mind bending, but functional.

Roundabouts too. But was on a recent Bahamas trip and their roundabouts are TWO lanes, and was in two accidents in two days (not driving) due to folks on the inside lane exiting while we were in the outside going around.

Don’t think cyclists should be on higher speed roads with cars. This doesn’t look like driving through suburbia. From the video, at one point it appears the bike lane crosses a right turn car exit. I’m guessing the area will be busy with cars. Seems dangerous.

^^^ There are pedestrian crossing signals for bikes and walkers.
They are timed with the highway stop lights.

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i knew that looked familiar. Think they have one of these as you're leaving my sons college. Less lanes but i think same idea. threw me off the first time through.

Most of the round-abouts here, are two laners...esp at busy intersections.

Very cool to see innovation in 100 year old technology.
Roundabouts are archaic inefficient garbage

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

The only round-abouts here are single lane (typically replacing a 4-way stop) intersections... and folks haven't adapted, or are slow to do it. The one pictured above is a "design disaster" imo, with two lanes. Never seen one.... how does driver on the inside lane that wants the next exit know the the outside lane is not continuing around the circle? What a fuster cluck design that is :(.

As for Raleigh, I worked out at RTP when I graduated .... there was just one "beltline" going through back then .... I get confused & lost there now :D....

signed....

Gomer

A two lane RA works esp good if you want to make a left turn. Enter the RA and get in the inside lane as soon as it is open. You can pass all the other traffic that is using the next two exits.
Merge back into the outside lane and exit.

Sarasota has a section of 'The Trail' that has three intersection in a row with two lane RA's.
There is only a city block between each one. The gray hairs really make it fun.:)

^^^^ Not here .... Aunt Bea and Gomer are just too nice .... they practically stop on I-40 to let someone enter :D!

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.

How's this for round-a-bouts

https://i.redd.it/s2flq2qvn8581.jpg

Rome's got one too.

https://thumbs.dreamstime.com/b/nigh...y-80751894.jpg

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


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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.

^^^ 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.

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.

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

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

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.

^^^ diverging diamond interchange.

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

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.

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.

http://forums.pelicanparts.com/uploa...1672615296.jpg

^^^ 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.

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.

http://forums.pelicanparts.com/uploa...1672619228.jpg

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.

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.

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/

Plenty of them in the ATL area already..!