Divine or Diabolical? - Building the Diverging Diamond Interchange (DDI) in Cities Skylines 2 

They converted a diamond into a diverging diamond interchange on my route to work years ago. The never ending traffic jam on the highway and surface street was ridiculous before. Now traffic flows through with minimal back ups during rush hour. It was such an improvement.

This would be cool if we had mods. Without it the logic behind the traffic light timing, it leaves something to be desired for me.

My only issue with them is some aren't exactly designed correctly for people like me who run oversize loads on longer heavy haul trucks. Otherwise i like them. I just don't recommend encountering your first one at 11pm during heavy rain where you can't see signs.

Been through a lot of diverging diamonds. They flow really well and the real-world "dangers" are exaggerated at best. Loved building these in CS1, can't wait to start building them in CS2.

10:20 One thing you can try is building them as alleys, since then you can get them closer together more easily, and then upgrade to 2-lane roads without keeping them centred to bring them closer together.

We have a Diverging Diamond Interchange just around the corner. It's fine. Throws people for a loop first time they see it, but fine otherwise. It was a big todo when it was first put in, for whatever reason the engineers had never heard of "lane math". 2 months in, they repainted the lanes, mostly makes sense now. Absolutely cannot fathom whatever idiocy is going on in the design room; I hope it's "management obstruction" but I have very serious doubts about some of the civil/traffic engineers in my state.

I have been wondering the usefulness of the complex curve and you just showed me!~ Thank you so much Yumbl

08:16 Hi, great video! Just wanted to let you know that the distance in the parallel road tool is in "zone cell squares", e.g 1 will have a single zone cell width between the roads.

I've ridden one of these in Roanoke, Virginia and it is set up in such a way that you do not feel like you are headed to the "wrong side". It feels like you are on a one-way road.

Amazing how good you were able to make that DDI with just the vanilla road tools honestly! The mod developers should have so much less work to do now (hopefully). Knowing that mods for advanced traffic lights and individual lane control are currently far enough in development to already be in-use by some players, makes me even more excited about the future of this game

I live in the city that built the first DDI in the US. We know them well. I've seen some other cities' implementations, and I cringe. There's a few key things these other states don't seem to understand. The key thing to remember that DDIs are a good choice when a high proportion of the traffic is from and to the freeway, and not so much through traffic. If through traffic is higher, build something else. One of the key things, from observing these up close, in the higher capacity bridges, you need a primary left-turn 'dump' lane that only allows turning on to the freeway. A key to traffic not piling up.

Always love a good DDI. Two-phase light, gets everyone across/on/off...simply beautiful.

Never seen one here in Germany so can't comment on whether I like them or not. But your thumbnail made me wonder how you got left handed medium roads as the overpass! I so much prefer CS2s node management over 1.

Diamond Interchanges are by far one of my favorite interchanges, love the video and the information given, thanks!

My city has a massive version of this. Huge islands. Two bridges separated over the highway and at a curve. The offramps do not intersect with the two intersections, they are on the bridges actually. Using it is easy, as there are wide curves before the intersections, so when you go 'straight', you are actually going straight and not really diverging

Very well done with the implementation! I drive through one of these almost every Saturday and it's always a joy.

The DOT just announced that they're building one of these in my city IRL. Can't wait to actually drive one

You're a genius. I tried and gave up on my DDI experiments. In CS1 I almost exclusively used these and they were super easy due to a wonderful mod. It was a reversed set of roads.

that's a wonderful method! Thanks, this steps up my interchange game even more haha. (Finally someone noticing the power of complex curve tools! I use it so much for rail and roads, but almost never see other people use it)

I just built my first one of these (before finding this video) yesterday in my city. It came out OK, but this one looks very polished. Love it! I also had some direct turn lanes to allow some smooth lane useage without the 90-degree turn at the top of the ramp. Thank you YUMBL. I have seen a lot of these things IRL. They look absolutely insane, but they work very well and have squared away many intersections that I knew to be nightmares before. A few IRL that I have seen: - I-55 & Weber Rd in Romeoville/Bolingbrook, IL (this is the one that I took inspiration from) - Route 17 & Route Rt 32 in Harriman/Central Valley, NY (this one is interesting because they were bound with existing buildings complicating/squeezing construction including a school and a major outlet mall. They also used a dog-bone roundabout within the same construction. Pretty cool to see. Great video!

The fact that you can make this intersection in CS2 without mods is really cool. Huge improvements over CS1. Not perfect, but much better.

Can you make an episode about system and services interchanges for urban expressways that’s entirely built elevated and/or underground in dense urban neighborhoods? How to minimize their land usage without sacrificing too much.

I lived in Anchorage, AK for a number of years. They installed a diverging diamond interchange at the northeast corner of the city, and it was...weird. It flowed pretty well, just took some getting used to. However. The interchange it replaced was simpler and OVERWHELMINGLY worse. Traffic there is workable now, whereas before it was unbearable.

LOL - Thanks. I hate to admit it, but I've never been able to wrap my head around the Complex Curve tool till now. Most excellent.

Brilliant work, thanks for showing how you made the DDI

I love the tricks, this is a really cool interchange. I am going to try it out, but I imagine it will be best used as a mid-level capacity interchage. Is there any way you can do an episode specifically about intrchanges with regards to high capacity traffic management in Cities 2? I am finding it difficult to build interchanges that handle high volume traffic in high density urban areas effectively. Also, an episode on high volume intersections would be very helpful. Your road hierarchy video was very helpful for traffic flow; intersections and interchanges for high traffic flow would be amazing. Keep up the good work and thanks for all you do!

the only improvement i can think of is to replace all the turn lanes with slipways and force the large road to go straight only. Cars dont turn on red at all so this is needed for the DDI to work as intended. the offramps in the video would then be left turn only and with the onramps replaced with sliplanes, you can angle them to make those barriers mentioned @11:40. I'm glad you made this tutorial, I had no idea how to get roads that close together before!

I love these intersections. I used to drive through one all the time in Superior Colorado. Much better than one of the interchanges near me currently. It's 2x3 (the extra lane is a dedicated turn) that is a 2x2 into the intersection, which is then a 2x5 on the other side of the intersection (2 left lanes are dedicated turns onto the highway, right lane is dedicated onto the highway, and the remaining lanes being straight.) then how the highway works is it's parallel one way roads along the highway that the dedicated turn lanes go into to then enter the highway. The issue is the right most left turn lane merges into the left most straight parallel and then diverges again into the highway. Like, they just need to put one of these there because the number conflict points here are insane.

As an IRL traffic engineer, I love DDIs for their safety and throughput. People just need to get over themselves and follow the signing/striping design. Also see roundabouts, which virtually eliminate fatalities by angling traffic to eliminate broadside and head-on collisions (the deadliest types), but that doesn't stop people from spouting off that "It makes me uncomfortable, so it must be unsafe." My only issue with DDIs is they're often designed to be atrocious for pedestrians by allowing continuous turns, or forcing pedestrians to walk along the median where it is loudest and most polluted.

I've never driven on one. Every fiber of my being tells me to keep to the right, so, I think driving one would freak me out. I'd be the person to make a hard right around the island into oncoming traffic! I use normal diamonds all the time in cities skylines, and when I need to increase capacity, I change it into a single point urban interchange (SPUI). I've never tried the diverging diamond so maybe I'll try one. I'm still in CS1 tho.

back in my university days, we had a diverging diamond at TN-66 (no relation to US 66) & I-10. Most of the traffic flows between the interstate in both directions, but only the south side of TN-66 to & from Sevierville (Dolly Parton) gets much traffic. as a result the main travel directions only go through one light (or 0 for right turns), which is nice. I drove through the DD from south to west once. It’s quite a large interchange and the through lanes approach the overpass at an angle, so it’s difficult to screw up. from all of the ramps and trees you couldn’t even tell you’re driving on the opposite side of the highway.

As I watch this video (good work on it). there is now a mod that allows individual lane control like tmpe did on CS1. I think it's called traffic. it is a wip and control of signal lights will be added. At the moment it just does lane control.

Onramp turns are collisionless, so it would be great if there were no traffic lights to turn towards the highway. Otherwise, when they have to stop on red and wait to turn, this divergent diamont interchange has exactly the same throughput as a non-divergent. Waiting for TM:PE for CS2 🙂

Great trick to create a beautiful "left hand road segment" in a right hand traffic world! Without a lane connection mod and an adjustable traffic light mod, I think this interchange does not add that much value yet. Without dedicated turning lanes and Without the possibility to have "always green light" for the turning lanes, the advantage of the diverging diamond, as you explained so well (when there is more turning traffic than straight through traffic), will not be met.

you can make the roads closer in the parallel tool, the two lane highway can get down to 0.25 units separated. I live right next to a DDI, I've not yet seen any collisions there, but I do see collisions at the standard 4-way intersection that's about 1000 feet away from the DDI. The truth is, the DDI has far fewer conflict points, so there are always going to be fewer collisions than a standard 4-way junction, which, IIRC, has 32 conflict points. Funny enough, there is a continuous flow intersection (not interchange) a few miles away that is very compact, and last night I saw a very bad accident there. The problem is, there aren't any signs that indicate where you're supposed to go, so when turning right, it's very easy to end up going the wrong way. They're getting very experimental with the roads here in Texas, but the 2 things that work for interchanges are displaced left turns and DDIs it seems. I know there's at least 1 dumbbell that was being planned for i35 south of San Antonio, but I'm not sure if they started on that or if it was scrapped.

10:40 when I saw your video thumbnail I thought how did he get it to be this close. And now this is the process... insanely funny 😅

The craze in my country is rather peanut-shaped roundabouts connected to highway on/off-ramps. Works well enough, people know the rules for roundabouts, and speeds are relatively low.

Great video as usual. One small note when in parallel mode reduce the gap from 1 to maybe .25 and it may make things easier to set up. I always come away from your videos having learned another detail which I have missed in my builds and your explanations are so clear and detailed that I don't have to guess what you meant by the instructions as you build something. While I am not a fan of diverging diamonds which may be from not having them where I live I understand their use in the traffic flow models. Keep up the great work man!

It’s absolutely astounding that mods which were on the original game are still not baseline in the sequel

as a european, ive never seen that kind of interchange here, maybe thats why i never got warm with it; but i like to watch u build it

It's good for traffic flow, but it ALWAYS misses the problem... Too many cars cueing and forming a line. That doesn't change lol.

smart design in real life because the left and right turning traffic onto the highway never need to see a signal to get on the ramps, unfortunately you cant seperate lanes from the light yet, but it still looks great, and will work great if a majority of the traffic is not going straight through like you mentioned

This would be massively improved with the traffic lights enhancement mod from thunderstore. It gives you the ability to control turning directionality per-lane, and has a right on red option. Meaning with proper lane maths, you can have traffic flowing constantly as it will allow traffic turning left onto the freeway from one direction, while also allowing traffic to turn right onto the same ramp from the opposite direction.

Okay the more I see about CS:2's new road building tools the more I'm liking them and considering buying the game. The only thing I think is missing is things like Move It's ability to precisely control the height of stuff

I've never seen one irl. But am amazed at how simple it is to how well it works, from what I hear. I was very curious to see how you pulled off right AND left hand driving in the game, and now I see it was just the simple "upgrade" manipulation. Good to know. I made an interchange in one of my cities today, don't know what it's called (sure it's got a name some where), but it looked like an elven medallion, lol. It's very similar to a clover, but it starts with the hwy going under the cross street (similar to a diamond), and the right turn slip ramps hug the curve a bit more (the armpit of the X) so they look nice and tight. But then you get two opposite crossing ramps parallel diagonally over the center of the "X", like west to north and east to south traffic goes up over next to and passing each other diagonally above and over the center of the cross, and then their opposite sides of traffic do the same but above them diagonal the other way (perpendicular to them), so it's 4 total different levels of an X over a Cross. And the way the right turn slip lanes stay snug, and the other lanes squiggle through and around to meet their target (do to over correction/shooting), actually looked quite perty. I was proud of myself, for a whole 30 minutes until I realized the amount of traffic I had all going to one area, through 1 interchange... the hwy was backed up to the neighbor city, lol. I failed to spread out my collectors on the arterial coming into the city so they where all backed up from there.

I made my own diverging interchange on my city, and my city is a population of 110k, and so far hasn't gotten congested the whole time. It's been very reliable and is a very high capacity interchange.

14:50 Good ones IRL also spread out the node even more and have you come in on more of an angle, so the approach road from the side street is pointed not straight at the oncoming traffic. You could try splitting the ramp also into 2 to do that, and maybe try to push the node bigger by temporarily using the 32-metre roads instead of the 24-metre ones to give you more connection space -- maybe even separate the offramp into two parts joining the same node. (Another trick you can use to try to make that happen is putting an extra-large roundabout there so you have more connection space, then delete the roundabout to get an ordinary node again.)

We have one local, instead of the ramps terminating at the cross point, they split, so highway traffic flows on and off the diverging diamond, without significant need of traffic signals. It's only the through route that needs the signals.

thanks for the tutorial! love seeing how we can implement good design into the game!

i love how intuitive the game makes it to upgrade your diamond.

Hey YUMs, When they open the Workshop, I hope this will be one of your first contributions to it.

I was surprised at how remarkably easy it is to build one of these interchanges in CS2.

Diamond Interchange wehave one in our town it was big deal and costly when they put it in but its very nice once you know how to drive on it

Have one next to my home. Previous to the reconstruction of the intersection the traffic was horrendous. After the realignment for the diamond, everything runs smoothly. “Championsgate Fl diverging diamond.”

Well now I understand the complex curve tool, thanks!

Best thing I think is needed is the ability to "create" your own roads or intersections! Feel they are a bit too tight/condensed at times

That's great, thank you. We don't have DDIs in the UK and I wondered how they work and what the benefit is. Really wanting the 'Interchange Editor' back but there's been NO mention of it from CO. I'm getting worried that we're going to have to build every interchange every time we want it. :(

The flaw here is you need to give the "left" turns direct access before the intersection, then make the traffic lights straight only. Right now it is just a normal traffic light, with both sides of "straight" traffic red at the same time to allow turning, which differs from a true diverging diamond.

I’ve noticed that in parallel mode that’s it’s one zone tile apart if you incense it to 2 it’s 2 zone tiles. Also you can decrease it lower then 1 so you don’t have to manually move the roads over.

Nice tutorial, thanks. I think you might be able to control lane turning by adding a diagonal one way highway in and out of ramps into the central street, then downgrading into one road the line between the diverging juntion and the one way out/in. Disable turning and traffic light on the streets going in/out from the highway. Therefore, people who wants to turn shall not wait for the signal to turn green, becuase they could turn before in the diagonal streets.

You dont need a stack everywhere :D I felt that

Thank you, didn't know about these IRL.

The Tropicana overpass in Las Vegas has been working this way while construction has been running.

Thats pretty neat! I wonder if it works with a roundabout too (given theres a no entry sign on the reversed lanes)

One thing I've noticed is that the diverging diamond seems to work better with people when there is a longer visible lead in to the crossover, but when there are busy intersections on either side of the diamond people seem to lose their minds entering.

One of the big real life benefits of diverging diamonds is the simplicity of the traffic lights. Gone are the timings for left turns, allowing rights while other flows are doing lefts, and allowing for straight through traffic. Instead there are two simple coordinated lights handling straight through traffic. One direction is go and the other stop. None of the flow to or from the highway are impacted as they have all become right turns. It seemed weird the first time through, but you quickly get used to it. And the traffic speed up is amazing. I am new to cities skylines but I have seen that the traffic lights seem completely brain dead. It really needs a complete traffic light planning system for busy interchanges with load balancing. Of course it also needs to resolve brain dead drivers. So far, I think all the drivers in the game are constantly on their cell phones!

Great video and this worked like a million bucks! It isn't as pretty but I set the spacing to .25 and it worked without the "bumping".

If you are having two bridges anyway, then a valuable alternative could be to build a large roundabout, crossing the motorway.

Was on this nightmare last evening. The twin city's has so many of them. Some with the tram going down the middle

The only improvement you can do to make this better is to make the on/off ramps be separate from the lighted intersections. The vanilla traffic light system handles it quite well.

DDIs have a massive flaw which is pedestrian accessibility. Which is fine if you're mot using it inside an urbanized area, bur if you are, well...

I can't wait for you to put all your awesome interchanges into the PDX Mods once they put it out.

not about the diverging diamonds but in california at least, if your merge lanes are THAT short, you will get multiple accidents per hour

mod for finer lane control is already there afaik... Biffa showed a mod, in a video 4 days ago, called "Traffic lights enhancement" that gives more control over the turn lanes.

There’s a diverging diamond at an overpass northwest of Indianapolis and I hate it because each side of the overpass has a two intersections, there are 4 intersections (stop lights) so get across the bridge, and you can turn right at the first intersection, but not the second one

I think this would work better if you change the on ramps to be slip-lanes that merge together. You could do the same with the off ramps as well, and have a diverge going each direction to merge with the road. This would avoid traffic waiting for lights to enter/exit the expressway, which is how they work in real life.

informative as ever - great video!

There a mod that allows setting arrows and setting up some traffic light rules called C2VM TrafficLightsEnhancement. the lane arrows only work if you have a traffic light however.

Hello. 8-lane road allows to create longer ramps. Then you may update 8-lane ramp to any road you need

Join Biffa on the dark side. Use the lane controller available now. It’s not broken any of my saves so far

We just had one put in on the new airport exit in Kenner (New Orleans) it is the stupidest thing they have ever done! There are more accidents than ever before! Traffic is a nightmare!!!

The one way roads in the diverging diamond can be nudged together incrementally by using replace tool but turn off snapping. It at least worked for me.

In my opinion the DDI is an american solution to an american problem. Because of the massive car dependency they need high capacity service interchanges at every mile marker, so the benefits of low-delay two-phase signalled turns onto and off the highway seem overly appealing, while the massive downsides (very low connectivity across and _zero_ accessibility for anyone not in a motorized metal box) aren't even considered as they are not relevant to public opinion. There is a reason more than 150 of them have been built in the US with almost 100 more under construction, while the entire rest of the world doesn't even have 20 in total... Parclos are usually as space efficient as a DDI, less expensive and have enough capacity while affording an at-grade non-crossing continuation of other types of transport (rail, bike lane, foot path) on the connector road.

Add slip lanes and disallow rights at the main interchanges

We have one of these near my house. It does look creepy when you approach but is very efficient and easy to drive once you get used to pulling into the 'wrong' lanes. I think I'll try this in CS2 without the extra movement. I'm not so patient. The game intersections are overkill in many cases.

We have two in Wisconsin that I know about. One in Janesville and one in Beloit, my wife hates them, it freaks her out! LMAO

6:19 it probably also affects vehicle conditions and therefore accidents. I do see an issue with the lane math where as they merge back down to 1 lane (possibly from no dedicated lanes?) they wait till last minute to merge, often hogging the left lane, and not zipper merging. I think the CS1 "lane math" is a bit out right now unless we have dedicated lanes, I've often had to just upgrade them into 2->4 (then reducing it to 3 then to 2) mergers so that they would merge properly and...that takes a lot of space but highways are cheap as dirt in CS2 so whatever doesn't back up traffic into the city. Could you have done it quicker with smaller parallel amounts? Say .5 or .25? 12:51 - and you can bypass the highway with other offset roads or create a VOP-like structure easily enough through the DDI if the through traffic is important. :) Split phased lights (there are EXPERIMENTAL mods - TM:PE or vanilla support would be preferred ofc) would be better 14:33 nah it's just unfamiliarity and it's not on a road test. Go to like Texas they don't know what a roundabout is let alone diverging traffic - and because they overbuild everything and everyone has big trucks, they'll just plow right through the grass or small concrete pavement. Here there's a bit more jersey barrier and cars in the way...people complained at first but accidents and traffic are so much smoother now.

The one unit parallel space is in cell units

Diverging diamonds are really good for high traffic areas

every intersection causes accident. An intersection is build to redirect traffic, so there are always some conflict points

If you enable dev mode, you can at any time toggle left hand side traffic (for subsequently built roads). When I saw this I immediately thought of using it for a diverging diamond, haven’t yet built one though. Seems like the ideal solution, except I fear the game might screw up the traffic light phases because it thinks it’s a regular intersection (having both straights go at the same time). That would be fixable with mods though. Btw, there are some mods particularly for controlling lanes and traffic light phases, Biffa made a video about it and it might help you out a lot, and may also be enough to fix potential traffic light issues mentioned above.

Any way you could look into how we could do a Michigan Left in CS2 next?

Theirs so many of these in Missouri. I always wanted to try to build one

One is being built less than a mile from me! They're neat, but I think it'll confuse locals.

Some great tips here, thanks

One downside is now one of the freeways has traffic lights on it. the lower level people going straight through do not have to stop. The upper level people do have to stop.

After the semi ran into the bus, I realized I’m disappointed that traffic crash physics isn’t realistic. Where’s the traffic rerouting? The emergency vehicles? The angry drivers? I kid, I kid. 😅

Already a traffic mod that lets you control lanes. I've been using it.

IRL the biggest issue with DDI's is they mix poorly with cycling and pedestrian traffic. See Road Guy Rob's "Drivers wouldn't stop... even for an 8-ft CHICKEN! "

You could also make the bridge a six lane road and have the outer most lanes be unimpeded U-Turns.