Why your Diamonds should "Diverge" - The Diverging Diamond Interchange (DDI)

[@Doddibot]

Drawing all the movements with bus lines is a really clever idea, I love it!

[@calgar42k]

the very smart idea is to use a trafic light on the off ramp toward the crossing storage ! im curious to see how it works with high traffic coming from the highway !

[@krissp8712]

​@@calgar42kI don't think the offramp needs a light. Around 7:00 you can see that it should just naturally join the diverging bit on the bridge.

[@krissp8712]

Ahh, maybe you meant about the TMPE mod to prevent lane weaving though?

[@Bendigo1]

Something I noticed when I used a lot of DDIs is traffic seemed to get worse in the info map, even though it actually flowed much better. I think it is because cars are always stopped one way or the other and they can pile up pretty fast, BUT they also move through alot better on green lights, and you don't see massive backups for long. That is if you don't place a bunch of intersections too close on either end of the DDI. The DDI is probably my favorite interchange in the game, but can take a while to setup and get right.

[@GladeRiven]

Yeah, DDI's can confuse game logic on heavy traffic. A fix is to squeeze in a pair of small overpasses that replaces the stop light on either end - takes a bit more room because having to spread the nodes out and makes the ramps not look insanely steep, but traffic just FLYS through the intersection.

[@kgaming7599]

Why don't we flip highways and remove the need for DDIs 😮

[@DanielSmith-DannieD]

I think I'll start calling you "The Traffic Whisperer". You are a true wizard and your explanations make what is a complex mess for me something even I can clearly understand. As always, very informative. Thank you!

[@ZeroAnalogy]

I've seen several explanations of this concept from real world to simulator "experts" / presenters. Your use of the colored traffic flow lines from game finally allowed me to fully understand how (why) Diverging Diamond Interchange works (so well).

[@goldenhate6649]

The part thats left out is where these diamonds were primarily used initially. The first 3 of these interchanges all tackled the same problem: a 4 light system, 2 side roads and the highway. This setup is a traffic generating nightmare with conventional intersections. However, the diamond significantly reduces this congestion.

[@krissallae]

There a real interchange like this in Mebane, NC.... Took a little getting used to but works really well.

[@linapilchard1384]

You explained the DDI so well! I actually live in the first US city to really go all-in with these and I'm happy to see more people taking notice of its benefits. It didn't take too long for most drivers to adjust to, and it's so much safer. I wish every city used them!

[@zackerystout4730]

Springfield MO, the city I live in, had the first test Diverging Diamond in Missouri. It proved a success, and now many of the interchanges have been rebuilt as Diverging Diamonds.

[@silvsilvsilv]

Usually I can understand the interchanges and the logic behind them, but for some reason this one breaks my brain :D

[@YUMBL]

And thats what this video aims to help with :)

[@m-w-x8859]

We have one here, takes a little while to get used to, but definitely cut down on accidents

[@JoshColletta]

The only service interchange I like better (and would argue is more beneficial for a number of reasons) is the SPUI. But I really don't understand why so many people are confused by the DDI. The contraflow section, sure, seems foreign and dangerous, but it's no worse than two one-way streets intersecting on either end, simply at a slight angle to each other rather than 90 degrees. You know where you're supposed to go, you know you're not supposed to turn there, so the aversion to them is perplexing.

[@mavfin8720]

Well, they look strange...until you've driven one, then they're no more a mystery. I even got to have the experience of the 'before' and 'after' experience with the same interchange. Huge difference.

[@andrewsprojectsinnovations6352]

I'd also add that the crossover's oblique angle should actually increase safety. Opposing traffic is now more-or-less straight ahead, rather than off to the sides, greatly increasing their visibility.

[@TheSatiah]

Thank you for detailed explanation of this intersection's inner workings. I was aware of it's existence for a while now, but was unsure how to implement it in my cities. Now I know how to do it.

[@hanzheng8247]

We have one here and we are doing a study to remove it because of the ultra heavy through traffic on arterial level which fails the DDI big time. To be fair, it is still an very ideal solution in terms of signal timing/pedestrian accommodation if the bridge replacement/widening cannot be justified and funded any sooner.

[@YUMBL]

I think you’re right. The ddi is great when highway access is most important, but it minimal (no) benefit for through traffic.

[@Archeious]

I actually live close to one of the first DDI built in the US and it was so amazing that I had to include it in my city. Thanks for the video.

[@Archeious]

BTW the left turn for the freeway exit traffic get a yield here. :mindblown:

[@YUMBL]

Yield can work, but the one near me is signalized. I think it has two left turns coming off the highway.

[@Archeious]

@@YUMBL I guess I should be more clear. It has a signal but also has a sign saying you can turn left on red if the intersection is clear.

[@YUMBL]

Left on red. Nice.

[@TheSkyGuy77]

The DDI is really good! Now imagine one that has roundabouts at the next intersection on the road that goes over the highway

[@bazzakrak]

Ahhh Sir, as always a nice video with a good explanation of how it works, and using busroutes as visual aids was a nice touch

[@andrewsprojectsinnovations6352]

I would add an additional argument that most points of conflict appear to occur at a more oblique angles. This would greatly increase visibility, especially if buildings or other obstructions are crowding the corners of the interchange.

[@sethwilliamson]

You said it and it can't be emphasized enough... a key reason the DDI has become such a darling with real-world planners is that they can be retrofitted onto classic diamonds with very little capital cost, usually little to no changes to right-of-ways or imminent domain, and very little construction disruption. It's a heap cheaper to convert from a classic diamond to DDI than to convert a classic diamond to SPUI! Really good bang for your buck.

[@johnterpack3940]

I remember the first time I went through one of these IRL. Wasn't a fan. Very bizarre. Though I imagine I would come to appreciate it in time.

[@SnehalA]

Where I live, there are mostly diamond interchanges and the signal lights almost never work. We have terrible traffic issues. There are no lane markings or medians either, so a lot of drivers drive as if it's a single point interchange 😭 I wish they implemented this, it would make it so much safer and also reduce traffic jams

[@OldManBadly]

While the diverging diamond works well in theory, it has a single basic problem, which is that the maximum flow is about 50% of the total roadway. As you have to cross over at each end, the traffic has to be stopped for about half the time to allow everything to work out. So not matter what, it has a very hard limit as to it's effectiveness. It's clearly much better than standard, but given all the space this used, it's likely not the most efficient for the given area. Nice explanation tho! :)

[@YUMBL]

Its more efficient than other options with a single overpass. Thats really the feat of it. Thats it can be made from the infrastructure of a common, lower flow interchange. Cheap for a small city.

[@thefrub]

The fantastic thing about diverging diamonds is that the interchange can be converted from a standard diamond interchange with minimal work, just some new lane markings and concrete islands

[@Corum001]

YUMBL the civil articulate civil engineer! thank you. :)

[@Ramotttholl]

from what i hear from is the only thing that's kinda struggling with Diamonds that are changed to diverting. is the walkability. whilst the crossovers are smaller with separations, there often around corners and cars can't always see ppl waiting to cross. because its converted there is barely any space for walking ppl. but in a game such as CS we dont have to worry about that.

[@Ian-uu7st]

I ban walking on my DDI's and build a seperate bike/walking path parallel to the DDI

[@mavfin8720]

@@Ian-uu7st Where I live, they put the pedestrian path in the middle, between the barriers, and the 'cross' lights at the ends allow access in and out of the middle at the ends. We have no issues with pedestrians or bikes with this system, that I've seen.

[@Arrek8585]

Funny thing is my area converted a diamond to one of these and managed to screw it up royally. They made half of the highway inflow into a weave instead of a sliplane for the right and decided the best fix was to make it a three phase light.... again.

[@matthew8153]

Never underestimate the government’s ability to screw things up.

[@TeamRAR]

Interesting use of bus routes for arrows on your diagram

[@wetfutzi]

I'm no fan of traffic lights. The diverging is way better then a normal diamond. But I prefer the single point partial cloverleaf. It's fully functional without lights and there is only two lanes crossing other lanes. It's my alltime favourite.

[@TheFarix2723]

Yeah YUBLE, have you ever tried a variation called the Double Crossover Merging interchange (DCMI)? I just wonder how well it works in Cities compared to how complicated it is to create.

[@stevenbalekic5683]

I have one suggestion...The traffic lights priority should be getting the traffic off the highway ramps..and the secondary should be the across traffic (from one side or the bridge to the other) as it would have less traffic on it in a city layout or in real life.

[@YUMBL]

Thats certainly not always true. What direction is priority depends on a lot of things and is not a rule.

[@stevenbalekic5683]

@@YUMBL But usually it is because it's a worse scenario to have a highway backed up than a normal road. Plus I assume the highway and the crossing road is connected to the map edge? Good for highways but not basic roads as it is generally considered highway traffic levels.

[@YUMBL]

You should do whatever it takes to make none of the roads back up. If the highway needs priority, great. If the cross road is carrying more traffic than so be it. There is no rule.

[@ExperimentsOfThought]

Could you consider the count of weaves(moving sporadic conflicts) and (controlled) conflicts for both to compare? When I counted it seemed to me all that happened was we swapped out static controlled conflicts and longer wait times for additional weaves with “moving conflicts”. Which in my mind makes for more chaotic conflicts that could contribute to more accidents. Granted they maybe increased accidents of the minor sort as opposed to major T-bone accidents like we see argued in the comparison of roundabouts verse standard intersections. But I’m still on the fence about these intersections because my gut says they are just hiding problems into the flow of traffic. One example is off-ramp traffic needing to turn left to head into the right most lane for an immediate intersection after the interchange. In the standard interchange they have that opportunity to make that move pretty safely as all traffic is stopped and it’s a clear route to get into the right most lane. However the diverging Diamond is heavily reliant on solid line lane configuration where left turning traffic must stay in more left lanes and now we have a weave that must take place to accommodate the need for the traffic to quickly turn right after the interchange. However now all of the flow of traffic is involved and it becomes potentially much more dangerous to make that lane switch for both the right tune in the interchange and the traffic that is already in that lane. Especially if those in those right most lanes also are in a situation where they two need the opposite side lines for turning left quickly after the interchange. This interchange seems to me to trade off congestion on the ramps and arterial at the interchange for potentially increase speed and danger immediately after the interchange but camouflages it with so much focus being placed solely on the interchange. In the bigger picture it could be hazardous. Maybe I’m just pointing out that this like many other alternate interchanges are not the end all and each have their places and must be considered in the grander scheme of things not just in micro picture of things. 🤷🏼‍♂️

[@jacobbaer785]

I totally agree, there are many cases where a solution to one problem just creates more problems somewhere else. (Such as adding lanes to deal with merges) But In this case there is a solution. If the left turn onto the bridge is controlled by a traffic light, have the right-most left-turn lane be able to move directly to the right-most lane. Then there's no merging conflict at all. Also do the same thing for right turns if there is an interchange nearby on the right, have right turns be controlled by a signal so they can move directly to any lane. The latter could actually fix issues at many existing diamonds that wouldn't be helped by converting to DDI. (Hope the way I explained this makes sense)

[@ExperimentsOfThought]

@@jacobbaer785 in a diverging Diamond the left turn lanes can not get to the right most lane since it is occupied by the through traffic lanes running at the same time. This causes the need for two potential weaves. One from Left to right and one from right to left immediately after the Diamond to accommodate any one who is not planning to stay on the arterial and they haven’t been given space or time in the DD interchange to get into the appropriate lane. I believe this to be a common problem since DD interchanges really only plan for the Diamond itself and nothing outside the interchange. However most interchanges either already have or soon need frontage roads along the highway which often intersect immediately after the DD interchange.

[@YUMBL]

Many DDIs accommodate turning left from the highway into the right most lane as an option. It’s quite common.

[@ExperimentsOfThought]

@@YUMBL I’ll try and find something that illustrates that. And how it’s handled. I suspect DD interchanges just restrict lane switching further away or restrict which lanes can turn when forcing some traffic Further up the route. I don’t know. Still trying to work it out. My gut just still thinks (yes that’s correct my brain is also my gut 😆) that the allure of some of these newer popular interchanges simply eliminate options or bury more obvious issues into other less obvious places like the flow of traffic elsewhere. Not saying DD interchanges don’t have a place and are great in some scenarios. Just can’t see how they would be better than the current one that is so prevalent

[@YUMBL]

Its only to be used in high traffic flow situations. If an upgrade is necessary to accommodate a growing area but you lack space for a Parclo of funds for a spui.

[@sintsmeding2371]

Thank you for making these videos. Can you build more real-life interchange types, like turbine, clover-turbine, braided, windmill etc.

[@YUMBL]

Thanks! I think all of mine are real except for the single point parclo.

[@sintsmeding2371]

@@YUMBL I didn't mean to argue with that. Just hoping to see more video's of other configurations in the future.

[@brohvakiindova4452]

@@YUMBL Translation: Keep up the good work! :P

[@chrisfourfiftyone2612]

In many cases a vehicle may use the off-ramp to stop and check a trailer or other problem with the vehicle, so the missing traffic flow would be from off-ramp to on-ramp directly. Now they'd have to go to the off ramp and find somewhere off highway they can turn around and park. That could be a mile or more, maybe a mile square trip for a double bottom trailer. In the original design they can stop there on the ramp and passing vehicles will not be at speed, they will be at turn speed. Two conflicts exist, someone who wants to go straight through, (unless you build a wall to prevent it). Much safer to do a momentary stop on a ramp then the 4 lane. Additionally there is no dead lane shown in the off/on ramps where a vehicle can stop. What happens if a vehicle goes straight through the crossover? This reminds me of the crossover blocking cables, there's no room to stop without hitting them, even though the original agreement was to place these in the center of the divide they don't do it. Not one width of space there. Vehicle checks, driver swaps, mess with computers and phones, load adjustment, tire change. So take a look at how often you see a truck stopped on an on ramp, next time you drive.

[@YUMBL]

I dont think its legal to stop on a highway off ramp. They should probably still be looking for a safer place to pull off. The straight thru movement is blocked by curbs in a real life DDI. All those shapes you see in the road are curbs. I would not drive straight across in any vehicle.

[@grondhero]

Two flaws I have yet to see addressed, one of which has a fairly simple solution are: 1) What if someone coming off the highway needs to do a U-turn? There is no U-turn option without them having to wait, when an extra lane could simply be added to each side of the bridge to allow uninterrupted traveling. 2) The biggest flaw is trapping/delaying someone exiting the highway who wants to use a business that exists _on their side of the highway_ but on the side where traffic enters the highway. Say at 4:38 someone exits traffic from the lower left side of the screen and wants to use a business on the lower right side of the screen, they can't.

[@YUMBL]

I’ll help address both! 1. Not all solutions need to accommodate a U Turn, though this one actually excels at it. Though I don’t understand why anyone who presumably missed their exit would deserve priority and not have to wait. “Simply adding a lane” is extremely expensive in real life. 2. Businesses shouldn’t really be built on interchanges. Interchanges connect high traffic roads, and a road is a place for moving vehicles. Businesses should be on smaller local streets, away from fast moving vehicles.

[@traffic.engineer]

Many states allow left turn on red from one-way to one-way. So traffic exiting from the freeway does not always have to wait for green to leave the ramp. Unless the jurisdiction determines the left turn on red is not safe.

[@OldDeadMan]

I find that any benefit that may be garnered by using this method are outdone by breaking all the traffic conventions that were taught to make it work. The DDI's I've interacted with are more confusing and more frustrating, with most drivers unable to actually garner benefit from the change. It also ends up removing the ability to flow the through lanes with longer cycles, making them less flexible to changing traffic needs than even a base DDI. Note: I'm not contesting the theoretical benefits in a tightly controlled virtual environment. I'm mainly touching on the mental effect of breaking convention for a minor, yet measurable benefit to traffic flow.

[@YUMBL]

The benefits in real word application of this are well documented. Safety, traffic flow, ease of conversion. There are a contingent of people that don’t understand it, but they largely haven’t interacted with it. You really cant mess it up.

[@OldDeadMan]

@@YUMBL I haven't messed it up yet, just sharing my observations of it in the real world. 🤣

[@YUMBL]

Funny thing is it doesnt break any traffic conventions. If people follow the laws in the state where its implemented everyone gets through quickly. I’ve read nothing of a concentration of issues from drivers in a DDI.

[@OldDeadMan]

@@YUMBL You'd know better than I, then! 😁

[@danielwarren7110]

as always enjoy your videos but you also forgot the ease of U turns as a benefit

[@he1d1_]

Hey, it would be cool if you made a video covering asymmetrical roads and their uses.

[@YUMBL]

I did. It’s called “realistic intersections”.

[@lruss2004]

Actually, ALL of those right turns, in the conventional intersection, are potential conflict points, in real life, for two reasons: People making right turns don't always turn into the correct lane and people making left turns don't (in my experience, less than half the time) turn into the nearest lane. So it's a simple situation where people who think that they are not doing anything wrong are creating additional conflict points.

[@YUMBL]

Very true. Most areas have laws that mandate turning into the nearest lane. Though i suspect it mainly interests insurance companies when its time to decide who pays for the accident.

[@kurtgarrett6993]

Same thing as going to Sevierville on the way to pigeon forge

[@rudigermullins8343]

Another great design Yumbl, though these must be very popular in USA. I wonder how confused American drivers get by "driving the wrong way". I try not to build American style cities, and I cannot think of any near me in Germany. What is next? a double crossover merging interchange This should be a worthy challenge for you 🤔) ?

[@YUMBL]

You really can’t mess it up as a driver. Getting to the wrong side would take effort from a UX perspective.

[@retha90]

No confusion from me. I just follow the road, and it doesn’t feel any different.

[@5blocksmc979]

the diamond interchange can be done with 2 phases if you have people turning left onto the highway yield

[@YUMBL]

Is that possible in current traffic manager?

[@5blocksmc979]

@@YUMBL idk EDIT: in real life it works though

[@5blocksmc979]

@@YUMBL UPDATE: yes

[@7th_CAV_Trooper]

I have the asset used in this video, but can't find any similar assets in the workshop. :/

[@AudryConsol]

I don't know if you've done it before, but I'd love to see a comparison between a ddi an spui

[@YUMBL]

Same! Let’s do it :)

[@joebass5163]

Should the right hand turns be traffic light controlled or free flowing? Tulsa, Ok is implementing a DDI and although the graphic they used might not be final it appears to have traffic light controls for the right hand turns exiting and entering the ramps.

[@YUMBL]

Either depending on traffic volume, available space, and cost. If theres not much right turning traffic stopping is fine.

[@wendychan4012]

Heh, converting to a diverging diamond is cheaper in reality than in Cities Skylines. You can't just repaint the lanes ingame so you'll have to rebuild the bridge.

[@teambellavsteamalice]

How does it compare to the Single Point Urban Interchange? So in cost, maximum traffic it can handle and maybe complexity?

[@YUMBL]

Thats a great question. The SPUI runs in 3 phases, and generally requires a wider overpass. With that said a lot of diamonds also become spuis. Id say overall a SPUI is better for supporting thru traffic, and the DDI is better for supporting highway traffic.

[@sherk3286]

Ive only ever seen one of these and it scared me

[@JCHall-uf2tz]

Would a flashing Yellow left turn arrow on the freeway off-ramp work so that traffic can yield a left and then there is an option to protect that left turn with a red arrow for on-peak traffic times or if the overpass is filling up?

[@mavfin8720]

Truth be known, that's a function of how much room you have between the cross-traffic light, and the on-ramp. There are five of these in town (Kansas&JRF, Kansas&I-44, Battlefield&65, National&JRF, Chestnut&65). On the north end of the Kansas&JRF bridge, there's no light, but there's a ton of space, so a yield sign does the job. Also, as an aside, the Chestnut&65 DDI has a problem: There's no dedicated 'dump' lane that only goes left on the south side. I'm guessing they ran out of room on the underpass and only did 2 lanes on the south (3 on the north), so the 2nd lane goes left *and* straight, so when it's busy the westbound traffic will pile up in the left lane, and cars going straight will pile up enough traffic to get in the way of the left turning traffic. The rest of them have a dedicated left-only lane on both sides of the bridge, going onto the highway.

[@wolframstahl1263]

I've long had an idea for a modified version of this, but so far I've only did it on paper, not in the game. Let's start with the layout at 8:10 and look at the lower/south half of the interchange. If we let the incoming red and green bridge over the opposite direction's yellow and green, we have the same setup without the traffic lights, but with another overpass (which needs to be mirrored on the other side). But we can add another benefit, we can let the red and green also bridge over the incoming yellow, eliminating the weave between green and yellow, making the whole thing free flowing and weaveless. Do you guys think there's merit to the idea? Or is it inferior to other free flowing options?

[@YUMBL]

Look up the “DCMI”. I think thats what you’re describing.

[@wolframstahl1263]

@@YUMBL That is precisely what I'm describing, thank you!

[@sandwiched]

What about the grade-separated DDI? Aside from increased infrastructure costs/complexity, are there any reasons to prefer this flat one over the grade-separated one?

[@YUMBL]

The dcmi would be better, but it would be painfully expensive in comparison. The point of the DDI is that its cheap and easy.

[@louiszhang3050]

DDIs are amazing. Unfortunately, I realize a lot of DDIs being constructed in the US are oversized. They are so big you might as well build another type of interchange in its place, and they are horrible for pedestrians. The version shown in this video are the best. They significantly improve safety and capacity, take the same footprint, and the slip lanes are angled aggressively to slow down vehicles for pedestrians before going on the highway.

[@ihatearial]

Its possible to make a expansive conflict-free version of this with a 3rd level of height. I've done it one time and had quite good results, also using an reversed avenue from workshop.

[@YUMBL]

Its called a DCMI.

[@ihatearial]

@@YUMBL Oh, I didn't knew that. Thanks!

[@yaqxs]

Could you manage these diverging diamonds without traffic lights? I'm just wondering, whom to set priority to, if a traffic light or both fail(s).

[@Aimless6]

When the power fails, yield to the right / traffic ON the bridge might just barely do. With the curve to switch lanes, speeds should be lower than on a conventional diamond.

[@martyburgess341]

While I was sceptical at first. Now I've seen this with a better explanation I am willing to use it as a potential traffic fix.But would Give-Way(Yield) or Stop signs do any better than (I am not a huge fan of)Lights?

[@zewhatyouwannasay]

I would heavily advise against using either yield or stop signs on this intersection. I mean, where could you add a yield sign? All roads are likely very busy (considering the six-lanes and intersection type). This would also mean stop signs would not only be more collision-prone in reality, but also slow and congestion-causing in game too. If you have the PC game, get the TM:PE mod. It’s a necessity for enjoying traffic management, and it allows you to place timed traffic lights, which can hopefully allow you to make the lights more efficient than the vanilla ones.

[@matthewparker9276]

In real life, all turns could be managed by a yeild sign, but you really need lights for where the traffic crosses, and in CS you can't combine lights and yield signs in the same node.

[@martyburgess341]

@@matthewparker9276 I know I am not able to combine light and signs on the one node. I was just asking what is the best option for these types of junctions.

[@hynekchovan3951]

Why not use a roundabout?

[@YUMBL]

This has much higher capacity. By a wide margin.

[@Johnjohnthejohn]

Never seen one in my life in the Netherlands

[@custardo]

There is (a temporary) one in Leiden. It's the intersection between the N206 and A4, at these coordinates: 52.16589858475824, 4.452340433419987

[@ivooo007]

nice!

[@duskmoon181]

I like to call it a Diamond with a touch of British m8

[@gforcemaybe3459]

What about a roundabout below the Autobahn as you can find at 48.0482094 North 10.8384856 East? It's more than 300m in diameter

[@davidjohnston3044]

Double roundabout is better. No stop lights and no place to get hit in the side.

[@YUMBL]

Double roundabout lacks capacity in comparison, but it is safer.

[@th5841]

@@YUMBLJust an idea, but what if we, instead of spending loads and loads of money and space on increasing road capasity, we managed to transport more people in each unit driving on the road? Like a longer car with several rows of seats. The traffic would be lighter and faster. Something to think about.

[@YUMBL]

I agree. But if such a thing existed NA would probably still just widen our interchanges instead 😉

[@theman-wq5on]

i do not think my diamonds should be diverging

[@YUMBL]

As you wish!

[@balexan530]

Worst intersection ever. Confuses drivers, does not work as efficiently as projected.

[@YUMBL]

Do you have a study that shows this? I’m curious about the projected figures as well.

[@matthewparker9276]

This is my favourite way to implement the diverging diamond in game. It doesn't work well with canola traffic lights, but with traffic manager and custom lights it can work very well.

[@joel9002]

What is a canola traffic light?

[@zanmatoer]

@@joel9002 presumably it's a typo from 'vanilla'

[@Bluerazor52]

@@joel9002 A traffic light made with canola oil. An alternative to the vanilla used in traffic lights in the base game.

[@YUMBL]

It has “slip” lanes ;)

[@ThatRandomBeast]

How does this compare to roundabout interchanges?

[@masonkpiano]

In my area, the county just updated one of our old diamond interchanges into a diverging diamond and I can say this really does work. It’s already been two weeks and there’s so much improvement on the traffic flow.

[@dyngbld]

We have a couple around here, They work great, I was surprised. Every now and then we get someone who can't figure it out, but it really did cut down on the congestion.

[@masonkpiano]

@@dyngbld honestly in my cities, I have either Parclos, or DDI for my service interchanges lol

[@Golinth]

Yup. Grew up in an area that had pretty massive growth over the last couple of years, and we had a DDI installed, traffic was massively improved. Very happy with it.

[@Tim_van_de_Leur]

What about pedestrian traffic? Safer for them as well?

[@dyngbld]

@@Tim_van_de_Leur Not a lot of pedestrian traffic in my area.

[@JaredJanhsen]

Highway departments should use your presentation style to show these designs to the public on real projects. It's such a fantastic explanation of how this design works and for the better.

[@Bram06]

By using the bus lines you've clearly outdone yourself again. This is your most professional video yet. And it may even be the best video in generall describing the DDI.

[@GlenwingThink]

That reversed road asset is a real game changer in constructing these. At the end of the video I thought "but I wonder how he built it... it almost looks like the two reversed lanes are a single road piece". Then I thought, if it were a single asset, Yumbl is pretty thorough, he seems like the kind of guy who would credit all the assets in the description. And you were 👍 so thanks for going above and beyond every time. I want you to know it's appreciated ;D

[@custardo]

In sim games, by all means, in real life...only for cars. DDI's suck for pedestrians and cyclists. If a DDI is planned, a separate over/underpass for pedestrians and cyclists should be a given. DDI's also don't mesh well with priority public transport lanes.

[@YUMBL]

Fair. I certainly think it favors traffic getting on and off the highway rather than cross traffic.

[@MoreDeiftwaser]

I remade my Diamond Interchange to include a diverge, helped so much it screwed over the traffic everywhere else

[@jacobbaer785]

So irl you can actually play with signaling phases a bit more than was demonstrated here to get more capacity out of a normal diamond interchange. The most common one is to let both thru traffic go at once, with no left turns allowed. This would be between your phases 3 and 1. I realize this can be difficult in CS. Another one is to separate the off ramp left turns into 2 separate phases. This can be structured so that traffic never gets stuck in the middle of the interchange (ie the bridge) but has the drawback that it takes longer on average to get through the intersection. I know you were focusing on the DDI here so this doesn't necessarily pertain to that, but i guess this would be interesting for someone who happens to see this comment.

[@YUMBL]

All true. And great to do before refurbishing an overpass/interchange unnecessarily. I feel the same about intersections. People often comment “that should be grade separated”, but a four way intersection can be pushed quite far without breaking the bank.

[@Shuno22]

Diverging diamonds are quite popular across urban areas in my home state of Indiana. They often work well and I have no problem driving through them myself. Others in my family struggle though because the intersection only reaches peak throughout during rush hour and the intersection is empty other times. Seeing traffic come the ‘wrong way’ plus the guide to the left is very helpful but an empty lane to the right as you approach has confused my father many times. He believes he must stay to the right and there’s little to no signage that says otherwise.

[@TXPhoenix79]

We have one of these in Round Rock Texas over I-35. The only difference we have is that there is also a U-Turn overpass for the left-turn highway-exiting traffic since Texas uses a lot of frontage roads next to major highways. Its University Blvd and I-35.

[@YUMBL]

The free u turn is a nice bonus.

[@thisconnectd]

how the fuck do people get through this? Pedestrians? Cyclists?

[@YUMBL]

kzbin.info/www/bejne/rp3Rq2Nqer-jg7M skip to 10:50 to see. Though theres no highway interchange where I really want to walk or bike. Because its a highway interchange.

[@Lankpants]

@@thisconnectd Pretty much hit on the reason why these aren't a good idea in real life. Increased traffic flow might not even be a positive goal depending on the scenario. In some cases it might actually better to do things to reduce traffic flow and encourage the use of alternate modes. That logic does not apply so much in Cities though. It'd be nice if the game was a little less car centric, but it is what it is. This video serves as a useful explanation for the game. I'm personally of the opinion that free flowing interchanges and highways in general kinda suck and we should be doing things to reduce their prevalence, not try to make them flow more freely, but understanding them is pretty useful for Cities.

[@thisconnectd]

@@YUMBL that's ridiculous interchange means change of modes you go from grade separated car area into place where people exist. Cars are guests in the city

[@thespartanmk1]

Ever since I first saw one in Lehi Utah and figured out what the idea of it was, I kinda fell in love with it. I think Diverging diamonds are rad. The Salt Lake area has a few unique traffic reduction ideas. There are a few intersections in Draper that don't allow lefts at the intersection. Instead the 'left' is a quarter mile down the road in a protected U-turn intersection that allows traffic to flow into a shopping center or back to the intersection into a protected right turn. Another road in Taylorsville has flex lanes that change their direction of flow depending on how much traffic is present at that time. The edge lanes are always their original direction, but the inner lanes can change as needed allowing for more options in either direction. Along Bangerter Highway there are lefts that start about a quarter mile before the intersection it's self. It's a left turn only light synced to the main light. That left takes you across the oncoming lanes and into a lane on the far left of the highway. That way when the highway gets it's green you can safely turn left off Bangerter without impacting it's traffic. There's a lot of Single Point Urban Interchanges all along the 15 and Bangerter now too. As a Californian that was used to typical Diamonds, clover leaf, and the likes; it was a bit strange at first. But once I had a chance to use them a few times and understand them, I grew fond of them. Salt Lake really grew up into it's own with transit in mind. It's not always perfect, especially with how the 15 could get at rush hour. But, I always found it a lot easier to get around than being stuck in Southern California freeway parking lots. Kinda really miss being out there. Maybe not downtown SLC, but the surrounding areas were pretty great.

[@jackmerrill8424]

God damn, you are my fucking favorite, your explanations are the best and your vision is just so logical and beautiful. How do I tell you I love you

[@Marconius6]

I was gonna say "just put a roundabout at both ends!" but I think that would actually create way more conflict points.

[@dogchan8860]

Ahh, i always take the diamond interchange in my city, its the b3st ngl...

[@ValdemarNorman]

We have a ton of these i Denmark. Works like a dream.

[@HoshikawaHikari]

The flow is so satisfying to watch

[@DoomieGruntVentures]

One of the modern interchanges I like a fair bit. And of course, because I like it, everyone else I know seems to hate it.

[@7th_CAV_Trooper]

First, I love the way you use the bus routes to illustrate the traffic flow. Absolutely brilliant! Second, the way TMPE sets up light patterns is weird to me. IRL in the US all the through traffic would share a phase. There are some variations like having an offset on the through traffic where the first side to go green gets a protected left turn, then the left ends while the through continues, and the opposite side through begins, then the first side through ends a bit later and the opposite side ends with a protected left. So in your sample I would expect a three phase light, but the first phase would be both sides of through traffic, then protected left for both, then protected left for the ramps. This allows you to give more time to the through traffic stage. Third, this was a great video. It's the first time I really grocked the diverging diamond. Thank you, Yumbl.

[@Doddibot]

Are you talking about the light for the regular diamond? Because for a diverging diamond it's not possible for both through movements to share the same phase.

[@7th_CAV_Trooper]

@@Doddibot yeah, I don't know what I was thinking. I didn't really understand the DDI until building one.

[@YUMBL]

:)

[@methosmomomax7470]

This intersection saved my city. Every interchanged I used prior to this one caused major traffic issues.

[@gambital320]

I never saw one, in germany

[@lifesoframadhangaming7364]

if i were you i will turn it into Roundabout, just like my city but still great video

[@YUMBL]

Roundabout interchange has far less capacity than a DDI.

[@aubreyboterf9789]

You forgot to illustrate one more common move which is the u-turn from the highway .... exit highway, turn left onto overpass, turn left onto acceleration ramp headed in opposite direction. The Diverging Diamond handles this very well, however some interchanges that are not Diverging Diamonds will allow for a separate lane on the over pass for the u-turn traffic from both directions. This obviously adds additional cost because of the extra wide overpass or (in the case that the main highway is the overpass) a longer bridge with extra lanes underneath for the u-turn traffic.

[@NithinJune]

8:27 usually DDIs have left turns on red here

[@YUMBL]

Yep. One of them is red here.

[@georgiabrigand6793]

Very systematic and logical presentation. I've watched others, but this is the first time that I really understand how the D-Diamond intersection works. Thank you for the excellent animation !

[@AlMcpherson79]

A slight variation with the traffic lights would, in my opinion, be needed - the left-off-highway traffic might end up stuck behind some of the non-highway through that got green on the first but red on the second, so a red on the first just a few seconds ahead of the second would result in traffic that got through at the first probably getting through on the second. just one or two seconds long intermediate phase though. I do notice that the quickness of changing between phases in Skylines is unrealistic as real junctions do the light changes green to red then red to green, instead of all lights changing at the same time... (usually). CS does the simultaneous change, resulting in cars sometimes conflicting because the last cars of a green-to-red are still in the junction when cars at the front of the red-to-green start going.

[@dgoddard]

I live in Springfield, MO and we tested the first live Diverging Diamond interchange. At first I thought it was ridiculous, as did most. But after a couple of times through it I completely changed my mind. Now we have several throughout the town and they've all seriously helped the traffic flow in the areas they are in. Now, if I can just get them to stop putting in roundabouts, we'd be doing great. Nobody likes the roundabouts here. They build them too small and you end up stopping anyway.

[@mavfin8720]

Yeah, I remember hitting James River & National *before* the DDI, and the left-turn traffic always piled up on the bridge and got in the way. No more!

[@dgoddard]

@@mavfin8720 Oh yes. Going west on JRF turning north on National took almost an act of Congress. Now, it's just zippp and done.

[@mavfin8720]

@@dgoddard Worse. I was coming from Kansas (i.e. from the west), turning left onto the bridge, going north, right at 5 PM, worked at Mercy overnight back then 6PM =- 4:30 AM.

[@dgoddard]

@@mavfin8720 Yeah, that's what I was talking about. Got my east and west messed up. Damn old brain.

[@AISPs]

Next thing is how to combine it with texas-like frontage road. Btw for asian elevated highways there's not enough space to build wide diamonds, so they go with SPUI all the way, 4 phase traffic light because of frontage road too

[@worldofgreenhell]

Professional explaining.

[@Anonymous-nd3kw]

DDI is actually my most favorite service interchange! I use it every time even a trumpet is really more appropriate. I can attest that it is really effective, and even safer in real life!

[@psal8715]

Have on e where i live in utah, it really fixed a really broken interchange.

[@TURBOMIKEIFY]

They built one of these near my hometown back in 2015 (I think). It was the coolest thing I have EVER SEEN! Screw a roundabout (jk)! It still gets pretty packed, but two of the three towns have over 100,000 in population. And, the highway goes to the city. I miss my old neighborhood. I lived like a mile from this interchange too! People were scared to use it when it opened. I do 50mph when nobody is around on it. Lol

[@P00katube]

The last time I Checked..... THIS IS THE UNITED STATES OF AMERICA. AND WE DRIVE ON THE RIGHT HAND SIDE OF THE ROAD!!!!! WE DO NOT LIVE IN ENGLAND!!!!! BAN DIVERGING DIAMONDS!!!!!

[@patricktimothy8354]

I had no problem with the one in Utah I used. But there is one in Northern Idaho that has intersections!it is the most confusing interchange I have ever seen. And I live in Louisiana and have seen some absolutely idiotic interchanges here and in Texas.And there is a development company from Alabama that has the most idiotic entrances and exists to its shopping centers. One is so dumb,you make like 4 turns at intersections,drive behind the dumpster of a steak chain restaurant,then go through another intersection,then drive a winding entrance to another parking lot to get to the academy. This is the former Rest Area PICKLE PARK on i12 between Covington and Madisonville,Louisiana. Also highway 190 between i12 and Covington now has people have to drive 2 miles in the opposite direction to make a u turn to then drive 2 miles back in the intended direction to get to your destination. We have a lot of stupid people here who stop at empty merge points and still can't figure out roundabouts we have had for a decade now. New Orleans is supposed to get one,technically Jefferson Parish,for the new Airport Terminal. Hopefully it works. But please be careful if you drive up to Couer d'Laine and head north up to Canada.

[@kylecossette5044]

We have a DDI at 162nd Ave/Macleod in Calgary, AB if anyone wants to see a real one. It's absolutely brilliant , no crossing left hand turns. And if you want to see road infrastructure what not to do, check out our highway 2 through the city. BIffa's head would explode as there's no lane maths

[@randybryant5618]

I love building these and watching the flow of traffic. But I do a single point/diverging diamond hybrid. A pain to build but fun, I also set up my signals different.

[@cherriberri8373]

Like always, your videos are top notch. Awesome

[@matthew8153]

I’ve noticed in cities skylines removing traffic lights solves most problems. What few times I’ve reached the point where a simple diamond interchange isn’t enough I modify it to remove through traffic and add another bridge for that on a neighboring street. I’ve never needed to use a diverging diamond nor have more than two lanes each way. I always build my infrastructure without traffic lights or roundabouts and I can still have over 80% traffic flow regardless of city size.

[@WhatAreColors]

Think of a simple crossing. Even here we have benefits if one (yes only one) of the roads is lefthand drive. Going straight, left and right is now all very simmlar in terms of possible collisions. It is also not possible to have a gridlock anymore. It sounds insane but I think a city like NYC could turn all the one way streets and avenues into two way. IF all the Streets become lefthand drive while the avenues remain righthand. Maybe it would even work without traffic lights. It will never happen because real people prefer the system as it is and just the take a longer route around the block. But in a world with completely autonomous vehicles and where travel distance has to be a short as possible, maybe it could work. I hate the fact that I actually talk about utopia fantasies. I'm usually not like that at all. I love driving my car. What do you think?

[@YUMBL]

A cool idea. Even the DDI has its limits though. It would be easy in a place with lots of pre existing one ways though… 🤔

[@Imnotabot_12341]

i was thinking instead of having two traffic light areas you could implement small overpasses to get rid of the traffic lgihts and make it truly free flowing

[@wmason1961]

We have one of these near my home in Central Missouri. If completely got rid of the congestion at that overpass. Without building a new bridge.

[@stuart6478]

what about uturns? coming to the overpass you can just come around without stopping. it's more difficult if you're crossing but even then