What's Greater than a Roundabout, but Less than an Interchange? - The Uncanny Valley of Junctions

[Music] everybody welcome back i'm yumble and today i'd like to take some time to discuss something that's very near and dear to my heart but is also overlooked and probably misunderstood by the city skylines community at large when building a city in game or in real life you'll eventually have to cross two roads they'll have to connect traffic will have to be able to move between the two roads so you'll have a decision to make you'll have to make a junction of some sort or an intersection or maybe an interchange just as it can be helpful to think about road hierarchy when designing your city i think it can also be very helpful to consider junction hierarchy so on the lighter side you've got a basic four-way stop or maybe a through street with a crossing street that yields to the through street so just a basic intersection on the opposing side you've got full interchanges so you've got service interchanges for getting on and off the highway you've got system interchanges for connecting your highways together and in the middle i would say there are roundabouts and traffic lights in the center now there's this magical area that exists it's bigger than a roundabout and can handle much more traffic but it's still smaller than an interchange and less expensive because it doesn't require grade separation or the building of a bridge i'm calling this the uncanny valley of junctions in city skylines and there's a lot of fun there and there's a lot of interesting solutions that work very well now before we get into building and setting these special junctions up please feel free to subscribe below if you like city skylines content if you like talking about roads and road hierarchy and interesting intersections and junctions and interchanges or city skyline city builds i make videos every week so please feel free to subscribe to the channel it would mean a lot thank you please allow me to introduce interchange test map this is just a map designed to force through traffic through the center to test the validity of an interchange or in this case a junction just an at-grade intersection which brings us to our first contender today you know it possibly you love it doubtfully it is the continuous flow intersection so take a look at this bad boy it is a two-phase light you'll notice all of the traffic in the center gets to go all at once and then once they've had their turn left turns included the other direction gets to go all at once when the light changes there we go so it's two phase operation two phases in a cycle which is really really good now the feature that allows this to happen is actually this funny thing over here you'll notice there's this weird left turn in between opposing traffic this is called a displaced left in real life there's usually a median or a barrier or something here to help that traffic not get hit by oncoming traffic that's not a luxury i have in city skylines with the network that i'm using though it is a blessing to have a network like this in city skylines that's so unique and versatile so jersey griffin built this it's in the steam workshop i'll link this road this network in the description too but what that displaced left is really doing we'll see it on this coming cycle it allows the left turning traffic to go at the same time as the through traffic right turning traffic has the luxury of a free right turn on the outside of the displaced left so the right turns are all free the left turns are happening at the same time as through traffic which is unique when compared to other junctions so the continuous flow intersection has a lot going for it now we know that the displaced left is the magic behind this whole thing that is the magic principle that allows this to work the way that that is achieved is by having a separate junction back here that is timed with the same center traffic light so all of these lights are linked up all four legs have the same solution on the ends and on the lesser cycle it allows traffic in to stack up so including the left turn and the through traffic they're all allowed to come in and stack up and then the left turn has to stop to allow the traffic out of the intersection it's the same on the opposing side so it's basically swinging back and forth between these two states one downside of this at least in in game here is that i don't have a way to independently control the traffic coming out this would technically be free in real life they could just get out this right turning traffic additionally i don't have a way to not stop all of this traffic when these cars are going so i don't have a way to make the left turn independent of those right now due to limitations of traffic manager but with that said this is quite high traffic density and it's still working just fine that would increase capacity slightly though if we were allowed to have it would increase it a lot if cars were allowed to just step up to the line because these two lanes are free-flowing but yeah that's the those are the principles behind it i'd like to show you how to build this and how i made this with only one network in city skylines the way that i'm going to be constructing this is using a single network whereas in a previous video i was able to make it out of multiple networks and heavy use of node controller and it all became very it's a bit messy though highly functional this is a much cleaner way to do it a lot like my recent ddi video where we built a diverging diamond with a single cool reverse network this is called the eight lane road cfi short for continuous flow intersection and these are all about the same length i think one of them is slightly shorter but i'm not gonna i'm not gonna change it 24 is this 123 there it is yup one side is slightly shorter as long as you draw this network facing the intersection then it is oriented correctly you'll know you've done it right if the roads have a single left turn facing the intersection on the wrong side of traffic if you reverse this it'll look a lot different it'll look a bit weird right so make sure that they're all facing towards the intersection and from there it's really just traffic manager setup this is this is very very simple especially if you're savvy with lights and things for the legs for the outer legs the left turn will be displaced thusly these can all reconnect on the other side the lane math is also very good with this road for three lanes in three lanes out so it all it all kind of works out what i opted to do here is these two lanes will go to the middle and the right turn is essentially a pocket so anytime you see two lanes originating from one point two destinations that means that there's a turn pocket of some point of some sort a left turn or a right turn so i'm treating this as a right turn pocket and that's it for that this is actually a dead lane which in the earlier shot you would have seen that i had it filled in with intersection marking tool to make a median so if you do that on all the legs and then in the middle you can have a dedicated right turn and two through lanes of course [Music] and a dedicated left turn which because of the nature of the light i allow this to go into whatever lane they want they can they can party however they would like to but basically you do this on all sides should be the same the same shape all around now that all the lane connectors are set up i want to show you a fun side effect of the two-phase light setup that we're going to be experimenting with all day today i'm going to turn on a vanilla traffic light at the center so i'm going to ignore the ends for now they technically need a light but technically it doesn't matter because all the traffic will make it through the vanilla traffic light is a two phase light so it is a all opposing greens get to go and then all opposing sorry there's a better way to say it all opposing traffic gets to go in one direction and then all opposing traffic gets to go in the other direction which is actually exactly the light setup for what we have here of course in game generally the left turns gum up the works but if you're using this configuration the left turns are already displaced and therefore they are out of the way the only problem then is that the traffic is crossing over at these intersections and it's a bit it's a bit awkward ultimately i do recommend setting up the light properly but it can work like this if you really just want to send it you totally can no no problem there whatsoever it's gonna work with the vanilla traffic light that so many of us hate on the real setup for the light looks a bit more like this you'll set up a junction all around set up timed traffic light on all five of these intersections we're gonna hit add step i'm gonna do a minimum time of 15 max time of 15 just as a starting point just for like a hard light that that goes for 15 seconds and we're gonna allow one direction to go in its entirety so two greens the opposing direction can be red right or the the perpendicular direction i'm going to hit add add step and we're going to flip all of these so the greens turn red the reds turn green and the other direction gets to go while the first direction has to stop add editing the first cycle we're going to go out to one of our wings so i'm looking at the direction with the greens and what i want to do when these are green i want to allow traffic out in that direction and stop incoming traffic so same thing on the opposing side allow traffic out stop the incoming traffic on the other side it's going to be the opposite of that so let traffic in stop outgoing traffic let traffic in stop outgoing traffic save and then edit this to be the opposite so we're looking at the now it's the red side what was green is now red i know it's confusing i'm confused too green light incoming to get to the red light green light incoming the opposite can be true so green light outgoing on the other sides save start that should work at least as well as our vanilla traffic light except now we've got our protected uh we've got our outgoing turn protected here our outgoing uh excuse me incoming displaced left now has traffic stopping for it but that is basically it for the light that is the whole the whole shebang that plus a little bit of intersection marking tool and maybe a bit of node controller to spruce it up but the bones are all there for your continuous flow intersection and here we are on to the next one this is called a median u-turn intersection or some know it as a michigan left when you implement a a u-turn to go left in this configuration the center is working an awful lot like the continuous flow intersection so this is also a two phase light you'll see the traffic stacks up then it all gets to go then the other side stacks up and those opposing lanes will get to go as well the way that this works using this fellow as an example our jeep here when a vehicle wants to make a left-hand turn they can get in the left-hand lane before the intersection and then at the end here they end up turning around in front of oncoming traffic so there are many similarities to our continuous flow intersection but this achieves it by using u-turns and there he goes by using u-turns instead of a displaced left in another similarity between the median u-turn and the continuous flow intersection the light here will not allow me to allow the straight traffic to just leave as much as i would prefer that the straight traffic is tied to the u-turning traffic so as long as the u-turns are allowed to go the straight through traffic is allowed to go but the normally i would prefer to have a green arrow for straight traffic and then stop the left turning traffic these are all tied together so whatever this car has to do the other cars have to do too on the continuous flow intersection we couldn't let them flow in for free on this one we can't let them leave for free unfortunately though that would work in real life it's just a limitation of traffic manager i also have limited control over where they drive on the curb i've given them plenty of space for for a realistic looking thing but they tend to drive over the curb anyway and that's just how it is for this one you will have to use node controller and make it a either a custom intersection or a u-turn intersection so on custom it does allow you to use traffic manager on all the legs to create this u-turn in my opinion overall this is one of the most satisfying and elegant solutions to a high-density intersection in city skylines same footprint as that continuous flow intersection that i showed you but no need for a displaced left the u-turn is is really quite a nice option i think it's it's quite a nice thing overall and watching it just eat traffic is it looks so effortless the whole time i'd like to show you how i build this thing and how the lane connectors work and a bit about how the light works as well in city skylines of course when building this there's a bunch of different lane math configurations that one could go with but today i'm going to do a a four plus three road this one's from the big urban roads pack in the steam workshop and just like the continuous flow intersection i'm just going to face all of these towards the center that's good and ensure that all of your end pieces are either u-turns or custom nodes using node controller if you have any other any other type of thing is actually not going to work and some of them look downright wrong but i would flip them to custom just to be safe the lane connectors for the legs all four are the same but in this case we're gonna do the same thing with the the right turn pocket so the right lane is going to be doubled which mimics the way that a dedicated turn works in real life the left lane of oncoming traffic is the u-turn which goes to the all the way to the right lane because they are coming from this direction doing a u-turn and making a right which nets them a left-hand turn so pretty cool and then these two you can do whatever you want i'm gonna split that one there just to just to make use of all these lanes another very viable option would be to use a four plus four road in this position i just don't want to overdo the lanes this this uh configuration works quite well without the fourth lane but you can do it if you want and i forgot to mention in the last one i do recommend blocking off that middle section so that people can't change lanes because that gets kind of messy now for the center we've got three lanes of through traffic and one right turn that can go wherever it wants they're never going to use that third lane in for the setup but if we mimic this on all sides that is the median u-turn setup and that is the leg setup now all of the lane connectors have been set up and we've got traffic approaching once again i'd like to turn on the vanilla traffic light basic vanilla bro you changed all my lanes oh no it just added okay just added markings that's fine yeah but vanilla traffic light as stated in the previous example the vanilla traffic light is great when a two-phase setup is used that doesn't account for the u-turns on the ends ignore the u-turns those are going to be kind of good luck everybody else but as far as the center goes it's truly a two-phase light with that said the optimal setup once again is actually the same exact thing as the continuous flow intersection so the goal here let's do it select all of the concerning points so five uh intersections there or five nodes at least making up the whole junction setup timed traffic light add step let's do about the same thing i'm just gonna do 15 seconds min 15 seconds max that seems to work okay generally and same deal we're going to do one way green the other road red add step and we're going to flip that so all of the reds turn green all the greens turn red and the other direction gets to go and the first phase i believe this is exactly identical to the last one the first thing we get is greens get to leave yep so the direction that is green gets to leave on both sides the incoming turns red and the opposite is true of the other one so the outgoing turns red and the incoming turns green save and we'll edit the second one so now this one's red which means that incoming traffic can come in this might be totally backwards my brain is fried incoming traffic is allowed in but must stop yep and outgoing traffic is allowed out and incoming traffic must stop on the other direction cool save start let's see how that works i've either done it entirely right or exactly wrong no that's it that's what it is perfect so now everybody is able to uh make a u-turn cleanly without having this traffic come and bump into them but yeah beautiful that is the basic setup once again you can use node controller and intersection marking tool to your heart's content if you want to see examples of that feel free to rewind the video and take a look at the the earlier shots to see how i marked this up but yeah beautiful all good just as a big sideline to all of this traffic i haven't made mention of pedestrians or cyclists yet and i apologize for that these are all very car centric solutions but consider this we are getting the traffic flow of an interchange or very close to the traffic flow of an interchange while being at grade so that's so that's quite a feat and there's a lot of cars going through this central area so i really recommend quite strongly that you separate your pedestrians and cyclists from this scenario entirely something that's always viable is to allow a kind of a scramble where when all of the lights are red give a pedestrian and bike cycle technically bikes could use the could use this but i would try to keep them away from this but the the scramble is all of the pedestrian lights turn green for a moment while the traffic is red and let everybody cross all at the same time in real life you can cross diagonally when this happens in game you'll be limited to up down left right but that would enable usage with pedestrians in-game what i actually recommend would be a tunnel a small pedestrian tunnel maybe even build this up on a hill slightly like take move it and nudge it up a few units so that your pedestrians and bicycles can go sort of under the side of it on maybe two of the sides or something like that just as a solution with continuous flow intersections and median u-turns there are often alternate ways for bikes and pedestrians to cross here's another junction type that i consider extremely satisfying way more throughput than a roundabout but it's still not as expensive as an interchange it's a great option if you're looking for high density traffic flow at grade i would call this one a quadrant intersection or maybe a double jug handle potentially each of these curved roads on the sides are the handle of the jug just like a milk jug or something once again this is two-phase operation so we've got all of our traffic going in one direction until it's gone and then all of the traffic in the other direction gets to go and it just cycles back and forth back and forth and everybody gets to go the left turns are handled fairly uniquely on this one as well you might notice that it looks an awful lot like a partial clover leaf and it would function exactly like a partial clover leaf were it not for this intersection in the middle so keep that in mind the left turning traffic from this direction so imagine the quadrants are to the approaches left right if you reorient it it changes where the quadrants are but if you're looking at this road with a quadrant to your left as you approach you'll end up making a left turn by being in the second lane just like this oil truck and that oil truck is slated to go around this curve here and out the other side so you end up going through the intersection twice but by the time this vehicle makes it back to the intersection this light is already going to be green so they will have only waited one time to make their left turn then they just get to cruise through on the other end it's great also these are free flowing if you look at the ends in this direction there's no traffic light required for these two ends once again the quadrant is on the left so let's flip it oh of course the uh the right hand turn is is free in the intersection in that one but if we flip it let's change the orientation now so the quadrant is on your right while you're approaching the quadrants are in opposing corners so we get a couple different orientations here this traffic does have to wait at a light for oncoming left turning traffic and that's fine these vehicles are all making their left by going up here and making a right we'll get to see that from this perspective in just a moment so they get to go up and at the intersection it splits so the left turn pocket happens after the intersection for the way that i have this set up and just like we saw a moment ago they get to wait in their left turn pocket exiting traffic gets to leave for free that's free-flowing just like on a low and this is kind of like a like a b park low situation where this traffic has to wait for the traffic entering the intersection but then when that stops any second now they get to go up the other side of the jug handle and make a right for free overall it's i would say it's a bit more space consuming than the other two options but it works very very well i'll put it on three speed and we'll just watch it crush traffic works great two-phase operation is very very important allowing the left turns to use the jug handle rather than having them in the main intersection is crucial to this one that's something all three of these so far have in common is that the left turns have been moved somewhere else out of the main intersection to allow for through traffic to have a really a really uh relatively conflict-free time compared to your average intersection let me show you the lane setup that i do for this one and ultimately how to build it the build for this one is only slightly more complex than the other ones only slightly only slightly the light is also slightly more involved if i'm being if i'm being honest so two of the directions are going to be facing towards the intersection i'm using that three plus four big urban road once again very nice so two are facing towards and two are going to be facing away so the four lane will be facing away from the intersection and the three lane will be facing towards and the handles go accordingly so looking at the orientation of the tords and aways the handles i'm going to use this two-way median road from the big urban road pack at the origin of these i'm going to go up a few units just to make a straight line easy i figured i would make the straight part part a third because that seems like it might be aesthetically pleasing but that's about how that's going to go but 23 is still plaguing me and then we'll connect these and the way that the rest of the setup works let's start with lane connectors so this one's pretty easy the right turn is guaranteed to turn right the traffic coming out is guaranteed to turn right the left turning traffic gets to turn left and the rest is the rest is easy peasy it sets up a lot like a partial clover leaf if you've built a park low in the past this should be rather familiar so there's that one i am going to stop traffic from changing lanes in the middle and this is a bit different but easier so i'm going to click on this and hit control s and that just automatically sets up perfect lane math exactly as intended as exactly as what i would want in this situation oh except i don't want this to be the left turn only lane i don't like that aesthetically because there is no left in the intersection so i'm going to swap this one out for the dotted line there we go this the big urban road pack is also awesome because it has perform medians or solid medians so you can see the effect that that has here that's not intersection marking tool that's just built into this road pack so i love that so anyway lane connector ctrl s to set that up on that side that can work on the other side too and this will be mirrored on the top portion over here so that leaves the middle the middle on this one ends up looking rather similar to the u-turn i think so right turning traffic is taken care of back here so this one has no right turn so straight through straight through straight through and a left turn pocket so we're approaching with the jug handle to the right of us so that can be mirrored on both sides so left turn pocket straight through straight through the right was taken care of back here so no right turn there now let's reorient this so this traffic which was free-flowing gets to come right in and keep to its lane and there's no left turn in the intersection that's not going to happen there is a right turn where i'll allow them to turn right into any of those lanes whatever they want i don't really mind and then these can go straight across so math-wise lane math-wise it all works out fairly nicely and there's your center great i don't suppose i've forgotten anything that looks correct remember the right turns are back here i'm gonna set up that last one and then we'll do the light for this intersection the light only involves three nodes so of course the center node and then these left turning nodes so keep note that each of these roads functions a little differently and make sure you've selected the right ones the other ones don't need a light at all they are completely free flowing no yields no management whatsoever but these three need a timed traffic light so for this we're going to do something very familiar we're gonna say add step i'm gonna for now i'm gonna go 15 and 15. that seems to be the sweet spot for this map at least like you just need to hard time it for 15 seconds per per phase if it's a two phase light and and go from there so one direction gets to go add add step and then the other direction gets to go i'm gonna click all four so now this this way has its turn so for this traffic when it's green [Music] i'm going to hit edit and we're actually going to break out this light so the inner light on this road is going to get broken out so there's two different ones because we have an actual left turn here we can do that and while these lights are green the outflowing traffic can go [Music] the left turning traffic must stop and this traffic can go i think this right turn can always go and i think that this straight through traffic can also always go but we're going to let traffic in so let's mimic that on this side inflow can go right turning traffic can go straight traffic is allowed to leave and left turning traffic must wait a moment so that should be phase one or rather state one phase one state one same difference right the second state where the other road gets to be green will be the opposite here so the left turn gets to go so oncoming traffic has to stop outflowing traffic can go and right turning traffic can go so basically the left turn and the and the incoming traffic get flipped so once again left turning traffic can go outflowing traffic can go right turning traffic can go incoming traffic must stop save start that should be it i'm gonna get some traffic running through here in just a moment and here we go traffic is moving and grooving these are totally free-flowing the markings that you would have seen earlier would would show what a safe right turn looks like there i had it curb protected earlier but that is the idea you just let it run just like that the timings are up for interpretation this is a 15 second light on both sides which i feel like might not be enough this one would benefit probably from longer cycles the other thing that i would say about this one is because it's asymmetrical this road is massively benefited this road [Music] i would say is probably the main road of the two would be my hunch use this one as the main road because this one has to stop a lot more to let the left turns in so if you do have one road that is that is the more dominant of the two i could be exactly wrong but my gut says that the direction with the quadrant on the left should be the priority road when picking this another cool configuration to this or a way to to approach it would be to consider that the um you could build this around like a city block if you wanted to or if you had other other implements that you wanted that you wanted in the middle or if you wanted to have a parking lot coming off of this or what have you some sort of attraction some sort of something this wouldn't be a bad place for some little areas around and these streets could be connected elsewhere too this could be part of a one-way grid system that's somehow worked into an area this one's pretty versatile considering that it just spreads traffic out on the on the handles so keep that in mind as far as which one is the fastest or which one's the best i'm truly not sure i currently don't have a great way to measure traffic flow other than manually counting which sounds like a terrible way to spend my afternoon so if you have a great way to count traffic without having to count it manually please let me know how i can do that that would that would let me quantify each of these i just know that each of them is is better than a roundabout that's all i can say for sure in fact let me install a roundabout and we'll take a peek and i'll show you one last crucial option that will help where roundabouts have failed featured here is the most juiced up roundabout i can think of it's a four lane roundabout with a four plus two road running into it there are two potential lanes for exiting so i've got a shared you know a conflict-free second lane that's allowed to cross but it's also allowed to exit just so we can simulate two through lanes as often as you can you want two lanes of traffic to be allowed through in city skylines you can see here the first wave of cars is hitting it there is a i would call it a point of saturation that eventually is always reached on this map all of the through traffic eventually backs up on all sides so everything looks fun in games right now everyone's catching up this side looks like it might even make it but then as traffic starts arriving in in larger and larger quantities you'll notice that this roundabout which is juiced up i've got the the angles are right so traffic can go in smoothly the um what else the speed limit is reduced to 20 miles per hour within the roundabout there's virtually a slip lane the right lane is effectively a slip lane it's built into the roundabout but you'll notice the right lane is never going to be the problem the right lane will always empty out fairly quickly in this configuration it is simply the left turning traffic but mainly the through traffic that is going to cause this to buckle and you can already see we've been on three speed for maybe two minutes nope not even two minutes about one minute and 30 seconds at most and this is looking a lot different from the other examples though this is the same traffic density as the other examples in this video this is what the roundabout does so this is really the point that i'm trying to make everything preceding this exists in a world where you don't need an overpass so you don't have that added expense but you also can't use a roundabout there's an abundance of solutions that exist in that area before a city has to commit to building an interchange and this is very important i want to take this same configuration and i'm going to clear the traffic out i'm going to give the give the light the same shot that the roundabout just had but i'm going to install a very similar light one of these directions actually has some asymmetrical left turning traffic so i may add a lane to support that left turning traffic but let's see how a traffic light does under the same circumstances and before we go let's take a look this has made it we are two and a half minutes it has made it out out past these little extra connections on all sides this one is the disproportionate left turn backed way way up let's see how a light fares when compared to this roundabout here's the result with a traffic light so the same road the same four plus two which gives us a dedicated left turn and a dedicated right turn as well as two dedicated through roads and that is really what solidifies the victory of a regular traffic light a multi-lane traffic light asymmetrical road versus a roundabout it's the fact that the through traffic has a direct route that doesn't affect everything else around it other than causing everyone to stop in order to accomplish it but that's just that's just how it works conflict has to be resolved somehow a traffic light could be juiced up further by adding additional lanes i just wanted to prove a point by having the same roundabout excuse me the same lane math that the roundabout was using applied here you can see it's just it's just destroying it i've got all of the states set to between 10 and 30 with a flow of 0.2 flow sensitivity of 0.2 and you'll notice it's not it's not backing up on all sides the roundabout clearly was out here somewhere it was out in the in the great blue beyond this one everybody has to wait but only for a moment before all of the traffic is let through all at once um is it as good as any as any of the previous examples no no this is not as this is a four phase light whereas the other ones were two phases but i think it proves the point that there's a continuum from one type of intersection to the next and just higher than a roundabout on that continuum is a traffic light if you're willing to use at least three or four lanes to make it happen everyone there you have it some unique solutions to to common problems in cities skylines and in real life when when traffic engineers and and such don't want to build an overpass there's all kinds of options just because a roundabout is not enough does not mean you need to build an interchange that is objectively false feel free to explore these fun options or just do a basic traffic light a basic traffic light with a few turn lanes is um is actually leagues above a roundabout in terms of traffic flow so don't don't doubt that's all i've got for today though feel free to subscribe here if you'd like i make videos every week feel free to head on over to twitch as well i do live streams twice a week we also have a discord community and if you want to go above and beyond in terms of support feel free to join my patreon um that's it that's all i've got for today everyone thank you for hanging out i've been yumble i'll see you in the next stream or the next video

Channel: YUMBL

Views: 274,813

Keywords: continuous flow, interchange, intersection, roundabout, flow, traffic, problems, traffic fix, u turn, u-turn, at grade, jug handle

Id: OoFnIVCfHz0

Length: 39min 16sec (2356 seconds)

Published: Mon Jun 27 2022