That’s because cars will impact pedestrians about the same amount as a standard diamond interchange. Truth be told, I’d prefer cars not impact pedestrians at interchanges. 🤷♂️
If pedestrian traffic is considered, these can be nice exchanges to navigate on foot. I have done so at one that directed pedestrians to the middle of the bridge and at one where pedestrians were on the outside. Neither was confusing, or more dangerous than a typical diamond interchange. Both were well-signed and had warning lights that pedestrians could use for the crosswalks.
Feeders roads are likely why Texas doesn’t need this but I’m reminded of when I’m in Louisiana how CONGESTED these arterial roads get when everyone is forced onto it to hit the interstate.
There's been one in El Paso for several years (at Loop 375 and Spur 601). I went out of my way to try it out. It wasn't confusing at all. If I hadn't know it was a diverging diamond, I would have hardly noticed. There were three in Austin as of 2021.
@@MikeV8652 I don’t find it confusing at all lol. I meant the amount of congestion seen in Springfield or Lake Charles of all places is 100% planning. And Austin is the LAST place we should take any advice from lmao. The city that refused road and transit expansions and then tripled in population? What a mess. I used to adore that city.
@@chefssaltybawlz I was just trying to refute the implication that DDIs were unneeded in Texas. I mentioned that the one in El Paso is free of confusion, because that's the main complaint we hear from critics (not you). Your criticism of Austin is entirely justified. The two DDIs there were built by TxDOT. The third one that my source said was in Austin is actually in Round Rock. Lake Charles's problem is that the state politicians have argued for 20 years over the kind of replacement to build for the critically decrepit and overburdened Interstate 10 Calcasieu River bridge, while ordering LaDOTD to keep the old one open over its strong protests of danger.
@@MikeV8652 Indeed! Was in agreement with you and was just speaking in a general sense not for all of Texas especially El Paso so far from me lol. And YES, that bridge is a ticking time bomb, I sincerely hope we don’t see another collapse. It’s inexcusable how much they’ve let that bridge deteriorate.
Another flaw of the DDI is that sometimes it can pass traffic too well, leading to overburdened queues at down stream traffic lights when previously the traffic queued on the exit ramps and approached adjacent lights at a more metered rate
This was a very cool video. I’m working on a construction project in SC where we are building a diverging diamond interchange. I had the exact same wtf reaction when I first saw the plans/animations. But knowing it reduces crashes by so much makes me proud to be bringing one to my community.
I've been through DD interchanges in Round Rock, Texas and Atlanta, Georgia. The new interchange off of I-65 in Spring Hill, Tennessee (opening any day now) will be a DD.
used to commute through the ddi at 75/university parkway daily and it truly changed how well that interchange works… so much less backup. I never knew it was the largest in the country though. neat!
Crossing a freeway is always perilous. Even with a standalone pedestrian bridge, an oversize truck could possibly knock it down. The diverging diamond does significantly reduce the risk compared to standard interchange ramps and roundabouts.
Believe it or Not, Georgia has a Few as well. I-95 EXIT 109 (GA-21) is one that's been around for some time. And just Recently, one opened right about where I live off I-20 EXIT 190 (GA 388) in Grovetown. Despite Two Months of Delays due to weather, it was completed, and Traffic Issues have dissipated Significantly. So Yeah, Consider me a Believer in this Interchange, ESPECIALLY when it's biggest compliant (Pedestrian Use) is something you don't see unless you're in a Big City, which the majority of these interchanges are currently built OUTSIDE Of.
My previous house was just under a mile from the first diverging diamond interchange in that state. It was absolutely amazing and made that whole area so much smoother to drive through.
We just got one outside New Orleans for the new airport (built 4 years ago but the interstate improvement just finished). Louisiana drivers are already batsh*t crazy. I can't imagine how well they're handling the diamond interchange. We can't even get a two way stop right, and it's assumed that the shoulder is part of the highway to drive past all the stopped traffic.
The SPUI is also an excellent interchange for freeways and major surface roads. Memphis has dozens of these and planning more. They were introduced with the newer State Route 385 freeway added to Southeast Memphis in 1989. They have since replaced several diamond intersections with these in several parts of the city. This interchange accommodates all left turning traffic with two light cycles and all straight through traffic with a third cycle all traffic on the "surface road" is controlled at a single point and the freeway traffic moves through freely.
I remember when the first one of these interchanges was built in Lexington, Kentucky. It was confusing at first, but now it's just another intersection. The city of Lexington is planning more of them in the future for congested intersections throughout the city.
We had 1 built in Savannah GA at Us 21 & I-95. Being a truck driver at the time it was opened i definitely had a WTF moment my 1st time going through it. But all in all it was a hectic intersection & has stopped a lot of accidents.
Good video. Another advantage of DDI's are that they can be retrofitted into existing diamond interchanges - using the existing crossing bridge over the freeway. They also serve the same purpose as a partial-cloverleaf (loop ramps), which are used to address high left-turn volumes. So DDI's do a lot for how much space they require, with minimal structures needed. They are a great tool for highway designers. The one condition that they aren't recommended for is urban areas, with high pedestrian/bike/transit volumes. They are poor for pedestrian safety, since vehicles are mostly free-flowing.
Its possible, but the problem is if you are a pedestrian walking along the cross street, you have to cross 4 separate times. With a diamond, you can have two crossings (assuming you get rid of the "slip" ramps). So less risk.@@stephenhassler4596
I'm not sure I follow. If a pedestrian is walking along the cross-street, they encounter four crossing locations to get through the DDI. Some of those don't have pedestrian signals (though they can). With a diamond, there are just two crossing locations, so less exposure to vehicles. @@stephenhassler4596
What Stephen said. I haven't seen any DDIs with bike lanes but I would also expect cyclist traffic could be accomodated fairly easily if routed alongside the pedestrian paths. As a pedestrian, you're either shielded by traffic, being on the side of the road drivers should never be turning into (i.e. oncoming traffic); or you're directly visible and in the motorists' field of vision, crossing when they have a stop signal. Crossing the street is also actually achievable at a DDI, as opposed to at most other typical interchanges.
The diverging diamond on US 36 and Macaslin in Superior co confused me at first. But after using it for bit it’s way safer and more importantly way faster than the typical interchanges.
A significant portion of southbound traffic on MO 13 going into Springfield, MO makes a left turn onto eastbound I-44. Before the original US Diverging Diamond was built there, traffic could back up significantly, with limited left arrow time in the traffic light cycles. So even drivers not making left turns would get backed up as vehicles would wait to even get into the left turn lane, let alone make their left turns. The DDI made an immediate significant reduction in traffic backing up on southbound 13.
There is one in Woodbury NY in the Hudson valley and the amount of times I have seen someone drive the wrong direction is crazy and I don’t even live there, however I did notice the traffic getting into the diamond was much better than a normal NY interchange. It seems to be a good idea as drivers get used to them.
Seen more head-on collisions at NY Rt.17 and Rt.6 Woodbury Commons divergent intersection. Built specifically for the outlet mall traffic by the way. In general, the problem is not enough driver education about them.
I've got 2 within 5 miles of me. One is a welcomed change as it has really cut down on congestion. The other is very confusing because it doesn't have dedicated lanes for freeway bound/ramp traffic. So, if you're in an outside lane prior to the DDI, you'll find yourself entering the freeway if you don't change lanes before or during the DDI. I haven't bothered looking at any data since its been constructed, but it seems like that would lead to a lot of accidents.
I have driven through two of the three diverging diamonds in Pennsylvania, my home state. In Australia, the DD must have traffic going on the right side.
One kind of annoying thing about DDI's and SPIs (Single Point Interchanges) is that if you mess up and get off the highway and want to get back on, there's not an easy way of doing it, you have to go through the exit, go somewhere, turn around and get back on. Not a big gripe, but annoying.
I live in Springfield and drive through that very first diverging diamond all the time. They are going to build a new southbound to eastbound flyover ramp in another year or so. This should really help with the backups and crashes in the southbound direction, as 13 Highway abruptly downgrades from a high-speed divided highway north of the Interstate into Kansas Expressway, a congested major urban arterial road as it enters town.
@@edwardmiessner6502 I doubt a full stack because there's way too much development south of the Interstate, and besides Kansas Expressway won't ever be upgraded beyond its major arterial status. Most traffic on 13 Highway wishing to continue south cuts over on I-44 and uses 65 Highway into Arkansas. So, I could see eventually more directional ramps being built to provide direct connections between I-44 and 13 Highway north without having to go through the stoplights, eventually becoming a directional T built over the top of the existing diverging diamond.
I live in Utah and about 2-3 years ago they actually got rid of that specific diverging diamond interchange. I disagree with that data and question the the folks that came up with the data, a lot of folks by there who work close by have complained there’s so many accidents from that interchange, probably because most people here are not used to it. They got rid of it because of the growing population, traffic challenges, and also to accommodate pedestrians and bicyclists, they still have one several miles down south along I-15 at the state route 145 interchange in American Fork.
interestingly there are 2 that just opened in central Florida, due to growing population. These people may say (anedotectally) that there are many accidents, but are there as many deadly accidents as before?
There's a diverging diamond off exit 407 on I-40 in TN. which has been there since 2017. a buccees opened immediately off the exit in 2023, and has a roundabout leading to it. it is certainly a very confusing traffic pattern
I have seen diverging diamonds, and something I would call a double roundabout, which has what are essentially two roundabouts linked in their centers. I really don’t know which is better, but both are better than standard diamond interchanges.
Yes, those roundabouts (the dog bone and the peanut shape) are pretty cool, but they are definitely not divergent diamonds. Divergent diamonds make you drive in the opposite direction. I do like roundabouts too though, as well as DD.
I lived in Carmel, Indiana, a city that currently has 150 roundabouts and are still building them. The two freeways that run through Carmel use the double roundabout concept. They work great and have convinced me that the roundabout interchanges are the better way to go.
Roundabout interchanges have limited capacity. They are better for rural to medium-density suburbs. If there is high traffic generation (mall or high density residential), then diverging diamonds are better suited.
Additionally, roundabouts are much more expensive to construct. There may be less cost over time due to less signal mainteance. But if traffic volumes increase, the roundabout would be a financial loss.
I first experienced this in Virginia at I-64 and US15 and was amazed how easy it worked. Keep in mind that Virginia seems to have the most cloverleafs in the world. Now I see one in Norfolk in the city. I'm a fan!
I believe they are a good idea. They are very disconcerting the first few times you are driving on the left, especially at night. They should have a warning sign similar to roundabout ahead.
I mean, if the geometry is right, all you're doing is driving straight. It really shouldn't be that unintuitive. First time I drove through one (it was the one near Truist Park) it didn't register to me as a DDI until I was all the way through it.
A few things I really like about these: U-turns are more natural when added to the design than a typical diamond interchange. Traffic flow is increased because almost every single way you could pass through the interchange you wait for *only one* light, if any at all. The confusion aspect is almost exclusive to people not paying any attention at all, because they are extremely heavily signed.... there's arrows on the ground, lane painted lines, dotted lines so that you can follow the lane lines through the intersections, "Wrong way" signs, lights (which indicate crossing traffic), "continue STRAIGHT" signs, Yield signs, "North on Highway X to the left" signs, and more. If you follow any of the dozens of indicators, you literally can not get lost. It might take a few trips through the interchanges before you really grok what's going on, but "I went the wrong way" is a really, really difficult thing to accomplish. I've been through several in a semi. The first time (in SLC), I was like: "Uh, what is going on with this intersection ..." because I was a passenger, but as a driver, it's really easy to navigate and I quickly grew from confusion about the purpose of the interchange to really excited about them. I think, personally, that they should become the default for most of our Interstate interchanges ... or any other exchange with a high-volume road meeting a slightly lessor-volume road. The only caveat is that the ends of the exchange (where the lights are) *do* take up some more room than a typical diamond interchange due to installation of barriers and curbs to reduce any collision severity. While bridges might not need expansion, the ends of the exchange are larger in area.
They built one of these a few years ago in the next county over from me. I still don't like - it just feels awkward and wrong everytime I go through it.
Living in St. Louis the Missouri side of the area has a ton while the Illinois side barely has any. Because if this my Missouri coworkers all love them while my Illinois coworkers hate them
ITD is putting in two DDIs in Rexburg. Almost all the traffic here goes east off the US 20 freeway, so it's well warranted. Even just lights at the interchange would've sufficed, but I'm glad Idaho is trying to future-proof the interchanges.
We have one in Columbus, Ohio at Roberts Rd and I-270. I absolutely love it and get a kick out of driving people on it who have never seen it before because they get so confused when we start driving British style
First one I ever drove through was the Port Wentworth exit off of I-95 near Savannah, Georgia. Had never seen or heard of anything like that, but it was easy enough to navigate. That was back in 2012. I've seen several since then.
An alternative is just putting roundabouts at each end of a diamond. That works too. PS - Manteca has been anglicized. Pronounced Man-TEE-ka in English.
@@traffic.engineer Well it depends on the count, doesn't it? They're building a DDI with 2 roundabouts over the perimeter highway in Winnipeg. Better than lights, I suppose.
I travel through several on the Kansas side of the Kansas City Metro Area daily. Namely the ones at I435 and Roe in Leawood, Kansas, and I35 and 95th street in Lenexa, Kansas. The other 2 are both on I35 and 119th and I35 and Homestead in Edgerton, Kansas. All are busy, the Homestead one, serving as a gateway to the Logistics Park Kansas City complex. Another is at K10 Hwy and Ridgeview in Olathe
They are building one near where I live in Howland, Oh at the intersection of Rt 46 and Rt 82 . I have driven through one in Miami, Fl and one at the I-40 exit 407 for Pigeon Forge/ Gatlinburg and they are very easy to navigate.
The one in highland utah has since been changed. There are others in the salt lake city metro area (notably on bangerter highway) so i am not sure why the highland one was removed
When new, these DDIs mimic traffic calming techniques, forcing drivers to slow down due to unfamiliarity with the geometry. Wait a few years for people to become used to them and the accident rates will go back up. This happens with every traffic engineering fad.
Exactly. I think the reason collision rates are lowered is drivers are unfamiliar, are paying attention and driving cautiously, including paying attention to traffic lights and not trying to rush a yellow light, as a result. Once they become familiar, collision rates will rise as they drive less cautiously and pay less attention to traffic lights and other traffic. I don’t feel any safer driving through DDI than older diamond designs. I can get T-boned just as readily if drivers from other directions if they miss or ignore traffic signals. Between this and the double-roundabout, the double roundabout is safer as it reduces severity of collisions via reduced speed and angle of collisions, and don’t rely on traffic signals, and thus drivers obeying traffic signals. They also better accommodate pedestrians and bike riders.
@@trillbilly69 no, the bridge over the beltway was rebuilt in the early 2000's with a counter-flow design. it wasnt a "diverging diamond" but it was very strange.
Every couple months I wind up at the Diverging Diamond in Naperville and I know what it is and the theory behind it but everytime I run into it I roll my eyes at how confusing it is at first
A few diverging diamonds exist in the Twin Cities area. My main gripe is most of these have "no right turn on red" and "no left turn on red" arrows at the off-ramps where it seems yielding would be more efficient. I can see the use for the arrows being the traffic is switching sides at that point on the arterial and a simple yield sign would be a safety concern, but sometimes I feel a roundabout interchange would work just as nice while also maintaining traffic flow. Maybe on lower traffic arterials yielding would make more sense.
The reduced visibility to traffic that has just crossed the bridge and is returning to the right side of the road is one of the main reasons for prohibiting turns on red. Another is that crosswalks are in walk mode when the light from the exit ramp is red.
You also have one in the Twin Cities area that needs three-phase signals rather than two: I-494 at 34th Ave S. Take a look at the map, and you will see the reason.
Columbus. Ohio had their first diverging diamond on I-270 & Sawmill Road. It was "different". Years later, the adjoining suburb of Hilliard installed one at I-270 & Cemetery Road. It too was "different" but one gets used to it with usage. It can be "fun" with the right mindset.
There's an interchange in Ann Arbor, Michigan, about an hour from me, where yeah, the freeway off ramp puts you into a roundabout. That also eliminates across traffic left turns. But it doesn't work for extremely high volume areas - which this is not.
Roundabouta have limited capacity. They would fail with the high volumes at these interchanges. America installs roundabouts were they is lesser traffic. The UK solution is adding signals to a roundabout for higher volumes. In America, adding signals to a roundabout is sacrilege.
I have never seen one like this with a dedicated left onto the expressway and only one through lane going back to two lanes past the intersection. Why did they do that?
A Diverging Diamond Interchange is currently under construction in San Antonio, with two more planned. We already have one Displaced Left Turn Intersection, and two more being planned.
Wish SA would quit voting against an actual rail system. I will say I like that in Houston our road expansions came with the light rail system, bike lanes, and park upgrades in a voter referendum. People need options.
Yep, these are just as or more dangerous as diamond intersections if people miss or ignore traffic signals, or if the traffic signals don’t work! There are plenty of opportunities to get T-boned in a DDI.
I've heard they sign contracts for "X number of videos" so oftentimes even if a creator finds out they're still locked in for more videos. Dunno what would happen if they chose to break contract
BetterHelp is such a scam. The supposed 'therapists' aren't even licensed. Research for yourself though. Just be prepared for what you find out (going down the rabbit hole)
Yes. The intersection of US-50 and MO-291 in Lee's Summit is a good example of this. There is a roundabout on the north side of the diverging diamond to connect Blue Parkway with Jefferson Street. Instead of continuing north at the diverging diamond, MO-291 turns east and runs concurrent with US-50 for about 1/2 a mile before exiting and turning north.
I've seen them in the areas outside Memphis and Knoxville, TN. I think they work great, as the need for left turns across traffic is eliminated. The people I've personally talked to who express a dislike for the interchanges have very little to no experience with them.
Being Florida, 2 of ours in South Florida have stop lights within a couple blocks each side of the interchange and traffic blocks entrences and exits to the expressway. Finally people diving lanes getting off the expressway blocking multiple lanes especially trucks. There's the right way to do a diverging diamond interchange and then there is the South Florida way......
We have a bunch here in Utah. My only problem with them are ignorant drivers sitting at the red lights that have a sign right by them literally saying “LEFT ON RED AFTER STOP” and they are not turning. I don’t know how many times I have had to give them a little honk for them to wake up and go.
My sister-in-law lived in Springfield, MO when that interchange opened. We visited in 2010 and were completely baffled by it. I didn't know it was the first in the U.S.
Roundabouts are much more expensive to construct upfront, due to more right-of-way and greater stormwater management structures. They also have an upper limit on capacity, so they cannot handle the volumes a diverging diamond can. There may be less cost over time due to no signal maintenance, but only if volumes remain steady.
@@traffic.engineer oh please. i see traffic circles and round abouts all over europe and asia in major cities handling HUNDREDS if not THOUSANDS of cars and trucks and motos per day...i can be done in the usa and as it is in european cities
@@sgrant9814 And the European and Asian countries have proven the capacity limitations when they install signals at roundabouts. America refuses to install signals at roundabouts. Roundabouts have about a maximum capacity of about 25000 vehicles per day per lane. Two lane roundabouts max out at 48000 per day. Three lane roundabouts max out at 60000 per day. So if there are more than 6000 vehicles in the peak hour, it will start to lose efficiency.
Having been subjected to the DD interchange at the junction of I-44 and Rte 13 in Springfield, MO, I can attest to an “unintended” (or perhaps totally intended 🤔) consequence: massive traffic congestion virtually nonexistent before the intersections reconfiguration. On holiday weekends, a driver on Rte 13 might expect wait 15-30 minutes or longer to work through this traffic jam. In groupthink sessions among traffic engineers and DOT administrators I only hear the statistics you point out and lots of people slapping their own backs. These intersections are great for local arterial roads but not for highly trafficked trunk routes like Rte 13.
I am sure a diverging diamond interchange has its place. That 10 lane road in Florida surely is. I, however, am a proponent of the use of double roundabout interchanges. This is where the intersections of a diamond interchange are replaced by roundabouts. The advantages here are the absence of traffic signal lights and equipment, the flow of traffic is maintained saving on fuel costs and air pollution. I still believe the roundabouts are safer than the signalized intersections required by the diverging diamond.
Roundabout would fail there. The volumes are way over the capacity of what a roundabout could handle. Not to mention the construction cost would be a lot more upfront with no safety nor efficiency benefit. Roundabout interchanges are better for rural and light suburban locations.
The pedestrian experience is worth addressing. You can cross the highway, but you have four traffic crossings rather than two, and you have to walk down the middle between opposing directions of traffic. Probably a net improvement overall, but still another case of prioritizing cars over people.
I crossed I-435 at Roe Avenue in Overland Park, KS on foot many times both before and after the DDI was installed, and it was definitely better afterward.
The only advantage of a DDI for pedestrians or cyclists is you only have to worry about traffic from one direction at a time, assuming a driver doesn’t get confused and end up driving the wrong direction. Otherwise, it doubles the number of intersections. I prefer underpasses that go under the entire DDI as you don’t have any intersections to worry about and you’re not surrounded by the noise and stench of traffic.
That is why there are local roads for that purpose. This is an arterial to arterial-collector. The epitome of bad urban planning is expecting a pedestrian public space is next to an interstate highway.
So you’re fine with freeways dividing and breaking up communities, which include many who can’t drive? Infrastructure is supposed to be for people. It should accommodate all people.
@@chow-chihuang4903 Again, that is what local roads are for. Not everyone driving is local. Are you seriously expecting all interstate freeways to be reduced to 25 mph and have crosswalks every 300 feet? There is still a large number of drivers conducting intercity and interstate commerce, and forcing them all into the same facility as local traffic is pretty much the same outcome as a stroad. A local community should have facilities to be easily accessible without cars, but such development should not be planned next to arterials that need access management protocols.
