ฝัง
- เผยแพร่เมื่อ 9 มิ.ย. 2024
- Why your Diamonds should "Diverge" - The Diverging Diamond Interchange (DDI)
➤The Diamond Interchange is commonly used to move traffic on to and off of the highway, keeping highway traffic flow unrestricted and providing ramps for entering and exiting vehicles. It's also relatively inexpensive to upgrade to the much safer and more capable Diverging Diamond Interchange.
➤en.wikipedia.org/wiki/Divergi...
➤Reversed 6-lane road:
steamcommunity.com/sharedfile...
➤Mods Used:
Fine Road Tool/Anarchy steamcommunity.com/sharedfile... steamcommunity.com/sharedfile...
Node Controller: steamcommunity.com/sharedfile...
Network Multitool: steamcommunity.com/sharedfile...
Intersection Marking Tool: steamcommunity.com/sharedfile...
Traffic Manager: President Edition
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➤Mods Collection: steamcommunity.com/sharedfile...
0:00 Intro
0:40 Diamond Interchange
3:03 Diamond Traffic Light
4:26 Diverging Diamond
8:17 DDI Traffic Light
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#citiesskylines #DDI #DivergingDiamond
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Drawing all the movements with bus lines is a really clever idea, I love it!
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).
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.
There a real interchange like this in Mebane, NC.... Took a little getting used to but works really well.
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.
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.
Why don't we flip highways and remove the need for DDIs 😮
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.
What is a canola traffic light?
@@joel9002 presumably it's a typo from 'vanilla'
@@joel9002 A traffic light made with canola oil. An alternative to the vanilla used in traffic lights in the base game.
It has “slip” lanes ;)
How does this compare to roundabout interchanges?
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.
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.
@@dyngbld honestly in my cities, I have either Parclos, or DDI for my service interchanges lol
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.
What about pedestrian traffic? Safer for them as well?
@@Tim_van_de_Leur Not a lot of pedestrian traffic in my area.
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.
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!
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
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.
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!
We have one here, takes a little while to get used to, but definitely cut down on accidents
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.
I remade my Diamond Interchange to include a diverge, helped so much it screwed over the traffic everywhere else
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.
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 !
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.
Usually I can understand the interchanges and the logic behind them, but for some reason this one breaks my brain :D
And thats what this video aims to help with :)
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.
This intersection saved my city. Every interchanged I used prior to this one caused major traffic issues.
The flow is so satisfying to watch
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.
Fair. I certainly think it favors traffic getting on and off the highway rather than cross traffic.
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.
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.
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.
I was gonna say "just put a roundabout at both ends!" but I think that would actually create way more conflict points.
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.
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.
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.
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
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.
I think you’re right. The ddi is great when highway access is most important, but it minimal (no) benefit for through traffic.
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.
Like always, your videos are top notch. Awesome
I've driven on a Diverging Diamond a few times and it has been some of the smoothest driving that I've ever experienced at a junction.
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.
The free u turn is a nice bonus.
how the fuck do people get through this? Pedestrians? Cyclists?
th-cam.com/video/xlnz04EZpMQ/w-d-xo.html skip to 10:50 to see. Though theres no highway interchange where I really want to walk or bike. Because its a highway interchange.
@@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.
@@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
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.
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!
@@mavfin8720 Oh yes. Going west on JRF turning north on National took almost an act of Congress. Now, it's just zippp and done.
@@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.
@@mavfin8720 Yeah, that's what I was talking about. Got my east and west messed up. Damn old brain.
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!
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.
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.
@@Doddibot yeah, I don't know what I was thinking. I didn't really understand the DDI until building one.
:)
Great video and explanation.
You made me change my mind about DD.
The DDI is really good!
Now imagine one that has roundabouts at the next intersection on the road that goes over the highway
The yellow and green traffic flow cross over themselves TWICE.
Which is the " diamond effect " with these flow trapping each other on the overpass
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.
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.
BTW the left turn for the freeway exit traffic get a yield here. :mindblown:
Yield can work, but the one near me is signalized. I think it has two left turns coming off the highway.
@@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.
Left on red. Nice.
I drive regularly through a couple of these, which were built in the past few years. In my opinion they are much simpler to drive through and traffic generally runs a lot smoother.
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.
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
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.
this needs to be shared with every local transportation office
Professional explaining.
We have a few DDIs in the Detroit area (Overpass on University Drive at I-75 and an underpass on Big Beaver Rd at I-75) but SPUIs are much more popular, especially along the I-96 corridor in Novi where every exit is a SPUI. My county has been experimenting with dumbbell interchanges, having installed 2 recently (and people are mad about it even though there have been 0 crashes so far). There's a truck-heavy exit here and I really hope they change it to a DDI. It's a very wide overpass already so I think it's possible, but there are businesses directly next to the current ramps.
As someone whos been playing simcity since childhood, whenever i see someone build a city with left hand drive roads, I see certain advantages to it.
This is basically the best of both worlds.
I am from Springfield MO where the first DDI was installed in the US. There are now 4 or 5 more in the city. I hate them. Not because they are confusing. (Only one of them is because it goes directly under an overpass and is difficult to see the traffic pattern as you enter.) They make entering and exiting the highways easier, but they bring two traffic signals very close to each other on roads that are already congested and pull more traffic to them because it is easier to get on and off the highway. The result is traffic that backs up beyond the neighboring (also busy) intersections. You end up sitting through 2 or 3 cycles before making it through the entire mess.
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.
WOOOOOOO YEAH BAYBEE THIS IS WHAT WE BEEN WAITING FOR
THAT'S WHAT IT'S ALL ABOUT
WOOHOO
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.
Im going to upgrade my diamonds, good video
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
IRL I drive through two of these interchanges (at least) on my daily commute.
The biggest problem I see with them is drivers that mistakenly take the wrong exit. With other interchanges, they could get right back on the freeway, but with this style of interchange, they have to go far enough to make a U-turn, or in the case of big rigs, drive a big loop through urban streets.
This became such a problem at one intersection the intersection was redesigned to have the right turn lane coming off the freeway split and allow a phase through the traffic light to get right back on the freeway. It's a short phase, but annoys the crap out of drivers when there is no traffic in that phase. And the phase must cycle every time because the technology to sense a car waiting fails regularly.
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
YUMBL the civil articulate civil engineer! thank you. :)
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
DDIs make sense on true arterials, but the old fashioned diamond should be king in low traffic situations. I live near NY's I-86 and most of the interchanges are diamonds or trumpets, and they hardly ever have lights! Interestingly the only interchange that has a light around here is the trumpet, and I honestly think it doesn't even need one. I'm fairly certain the only reason it has one is because it's relatively close to a school zone so it can help the busses load and unload, but even then there's another light at the school to help with that.
Yes, the DDI is at its best at interchanges where more traffic goes to the highway or comes from the highway versus the 'through' traffic on the bridge. If the 'through' traffic is higher volume...don't use a DDI.
Literally just had someone nearly plow into me on the local diverging diamond late last night. I had a green light, but he then proceeded to flip me off for being in his way. *rolls eyes*
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! :)
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.
I haven't had much luck with the DD interchanges. Mebbe it's time for me to revisit, my traffic skill is a little better now.
We have a ton of these i Denmark. Works like a dream.
I typically do a 3 phase light if it is a heavy interchange.
The first time I went on one I was a touch unsure but the thing worked like magic.
We've got a couple of these and I always wondered why they went to them. Clearly when the lights are set up properly they're efficient. The lights on ours are set up in stages so you get the green, cross over, and then there's a red light, the other lane goes and crosses over, then they stop. Then your light goes green and you cross back over and continue out of the intersection. If traffic is low it takes so much longer to get across. If traffic is high people end up stuck in the crossover unable to go forwards or backwards and traffic backs up forever. Good to know it's just GA DoT being grossly incompetent and not a stupid design. GA DoT infamously screwed up the deicing mixture one year and instead of insuring the roads stayed drivable sprayed on a layer of ice turning most of downtown Atlanta into a skating rink - people died.
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.
Never underestimate the government’s ability to screw things up.
I have one in Leland North Carolina… took getting used to but now it seems normal
And another video with perfect timing for me. I now will have to put in a diverging diamond to help a service interchange in my city. Thank you again Yumble.
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.
Great explanation, what road did you use for the overpass to flip the trafic?
Thanks! Its linked in the description.
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.
Thank you for making these videos. Can you build more real-life interchange types, like turbine, clover-turbine, braided, windmill etc.
Thanks! I think all of mine are real except for the single point parclo.
@@YUMBL I didn't mean to argue with that. Just hoping to see more video's of other configurations in the future.
@@YUMBL Translation: Keep up the good work! :P
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
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.
I ban walking on my DDI's and build a seperate bike/walking path parallel to the DDI
@@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.
Interesting use of bus routes for arrows on your diagram
We have these in Atlanta too.
Have on e where i live in utah, it really fixed a really broken interchange.
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.
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.
Hey, it would be cool if you made a video covering asymmetrical roads and their uses.
I did. It’s called “realistic intersections”.
Are there other places where divdiamonds could be beneficial, or a nightmare? Could variations of this work in a street grid? Maybe a street grid with lots of one-way side streets?
I think in real life, you could use a blinking red light (or maybe yellow depending on the amount of traffic on the bridge) on the left turn off-ramps, but that's just not possible in the game. You would basically be creating a "left on red" situation.
I don't think that's really necessary, there's tons of green time for that left turn anyway, because it's in the "shadow" of the through traffic crossing back over.
The only real world diverging diamond that I had encountered was in Malaysia in early 2000’s and always wondered why they did that and now many years later I know why
Nice. One big problem though are the left turns off the highway. If the bridge is backed up they have no way to get in. The longer the bridge, the less of a problem, right? What happens if you don't have the space for a very long bridge. What's the best compromise to handle those left turns off the highway? Yield, no light?
In a real setup i think that the engineer would set the light up to let the bridge clear before letting the highway in. or you can run a lefts from the highway only cycle for as long as necessary.
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.
Either depending on traffic volume, available space, and cost. If theres not much right turning traffic stopping is fine.
if i were you i will turn it into Roundabout, just like my city but still great video
Roundabout interchange has far less capacity than a DDI.
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
8:27 usually DDIs have left turns on red here
Yep. One of them is red here.
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).
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.
Road Guy Rob does videos on this sort of thing IRL. Worth a look if you haven't seen him before. He did one on the DDI.
Hes got a few on the DDI. Love his vids
Double thumbs up!
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
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?
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.
nice!
Question: Would you pick this over the single-point interchange (SPI)? SPI is fun to make and it looks good aesthetically. To me, SPI is the single solution to every interchange given enough space to build.
I prefer a spui for most applications. The DDI is great when irl cost is a concern and the city doesnt want pay to expand their existing overpass
The big thing IRL is that you can convert an existing diamond into a DDI much cheaper, and with less slowdown of traffic versus an SPUI. Not so clear in-game, of course.
The killer for me (as a UK person) is that you would have to turn from the 'fast' lane. I learnt that you would pick your lane based on how fast you were going relative to the other cars and always leave and enter from the slowest lane. are there UK DDs?
There is no fast lane on arterials with left turns
Theres a diverging diamond interchange that our team bus took a few times when i played tennis. Theyre a marvel
How does it compare to the Single Point Urban Interchange?
So in cost, maximum traffic it can handle and maybe complexity?
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.
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?
The dcmi would be better, but it would be painfully expensive in comparison. The point of the DDI is that its cheap and easy.
I dont know if this would work but could you use a bridge/tunnel on each cross to remove the need for traffic lights?
You can! It’s called a “DCMI”