Thank you all for the interest in this video! The hypothesis presented is supported by real world data as well. Those who would like to prove the traffic engineering community wrong now have the control environment to show it! I appreciate your comments, but I really look forward to all of your thoughtful presentations :)
I'm curious about your traffic light setups. You set them up to be "only one cardinal at a time" but I wonder what would happen if you split up the 'straight through' traffic and the 'make a turn' traffic. so leftright for a while, updown for a while and then right/left/right/left and left/right/left/right (if you know what I mean). I see that type of light configuration a lot in my local city, where it allows for seemingly more throughput as a lot more traffic tends to want to just go straight and there's less traffic volume making turns. So it's set up so that the straight through phases are prioritized and last longer. It would be interesting seeing a video about different traffic light phase setups, depending on the traffic volumes. (Hell, I suppose there's even an algorithm you could run over it if you knew the makeup of the traffic)
@@YUMBL I agree with your conclusions. That said - something to think about. In the UK, a high traffic, high road count, high lane count roundabout like that would not be implemented like that. First there will be traffic lights. Secondly, lanes will always tend towards the outside - so you get into the correct lane for your exit and it works it's way outward so you are in one of the two outside lanes when you need to exit. That's how they get their large throughput.
Hello. Traffic engineer here. The magical (potentially frustrating) thing about intersections is that there is a lot of hidden complexity. While it may seem a simple case of two roads worth of traffic intersecting, this is incorrect. The efficiency of traffic flow through the intersection depends on many hidden variables that require a lot of thought both in real life and in game. In this case, the traffic lights are vastly optimal compared to a roundabout for probably multiple reasons, the most pressing as far as I can tell being the ultimate destination of cars passing through that intersection. For some reason, perhaps an unexpected result of the setup, it is evident from the traffic light time lapses in this video that the vast majority of cars are passing straight through the intersection as opposed to left or right. This kind of intersection greatly favours the traffic light. From a mathematical point of view, traffic lights benefit from very high flow from individual streams one at a time whereas roundabouts service multiple streams simultaneously at a lesser flow. Keeping this in mind, it makes sense that a traffic light would work better here since almost all the traffic has to cross the path of another stream. Roundabouts are much more suited to balanced directional traffic where the ratio between left, right and straight turning is closer (In actuality a perfect roundabout would have every car go to the right as then there would be zero conflict but that would defeat the entire point of having an intersection). This isn't a perfect analysis, indeed such a thing is impossible without extensive computer simulation, but I just wanted to highlight that I certainly think there are situations where a roundabout may come closer to or even trump a traffic light in a high density traffic scenario. Although you are correct in that people are very "passionate" about roundabouts when they are certainly not the solution to every traffic scenario as some people seem to think.
Very balanced response! Thank you. I have yet to see a spot where a big roundabout beats a light in a high density situation though. They just seem to break down earlier consistently. I havent found a source that confirms that either. The light seems to maintain flow due to its versatility when traffic starts stacking in a way that roundabouts cannot.
Within the roundabouts threshold it thrives. Space allowing you to build it in the first place. Above that and its backup city. Then countries seem to add lights to the roundabout.
@@YUMBL We do have Roundabouts in Australia where the side roads to the roundabout have traffic lights to allow the main roads to have a better chance of clearing the peak hour traffic. Then the main road stop and allow the side roads to clear. The main through road to the roundabout might have 2 or 3 lanes, while the side or local road has 1 lane. These lights are only activated during peak hour traffic times. It more like a hold back to avoid a frustrated motorist on the side road waiting 10 minutes to try to cross the main road peak hour traffic from trying to barrel through causing a accident (crash). Though as the traffic increases, they change these to full signalised intersections.
instead of ‘dealing’ with traffic, maybe reducing car trips would have a bigger impact on throughput than either a light or a roundabout- we should de-incentivise car travel instead of paving over cites with asphalt to cater to them- a generation of ‘urbanism’ that panders to motorists has gutted American cities, leaving us with free parking and stroads. It’s terrifying that terms like ‘walkability’ need to exist, what a deep hole we’ve dug for ourselves.
Now this I HAVE to watch!!! Edit: Interesting video. Question: did you turn on the TM:PE Traffic AI at all as watching the roundabout with all the "not really giving way" that kept happening I'm not so sure it was on then?
I'm with you, @biffa... I know your way of setting up roundabouts, and I agree with it, but @yumbl makes a good point as wel, had the same experience... both have a use and place :)
@@YUMBL No I saw that, I mean in the TM:PE settings menu you can turn on the Advanced Vehicle AI. With this the game can cope better with a lot of things, particularly these alien builds we love so much, called roundabouts and the yield signs added with TM:PE. Without it the game seems to work better with traffic lights, which are a part of the game like stop signs. But with yield signs the game tends to need the Advanced Vehicle AI to help them get how they should work. I normally go for around the 70% mark :-)
I've done a research paper for university on roundabouts as a civil engineering student and my conclusion was that roundabouts are more effective in areas that have stop signs (or lower traffic volumes) rather than traffic signals (much higher traffic volumes). Arterial roads wouldn't benefit much from roundabouts as the volume of traffic is immense. Collectors and local roads have a much better benefit with roundabouts as the traffic isn't as demanding. While this video is a great example of how effective traffic lights can be, it wasn't optimized to the fullest extent as it appeared the left turning traffic was far fewer than through traffic. Maybe setting up a protected left only for a minimum of 5 seconds and then through traffic only for your times would improve the efficiency of that intersection even more.
All entirely true. I wanted the light to be easy to set up as most of the community swears by roundabouts. A good light will decimate the best roundabout. Now a lighted roundabout…
Yea. Once you add a light most of the charm and appeal of the modern roundabout disappears. The reasons people like it and such. Still probably safer than a regular intersection, but large. Efficient, but at what cost?
@@jacobgathman289 We do have Roundabouts in Australia where the side roads to the roundabout have traffic lights to allow the main roads to have a better chance of clearing the peak hour traffic. Then the main road stop and allow the side roads to clear. The main through road to the roundabout might have 2 or 3 lanes, while the side or local road has 1 lane. These lights are only activated during peak hour traffic times. It more like a hold back to avoid a frustrated motorist on the side road waiting 10 minutes to try to cross the main road peak hour traffic from trying to barrel through causing a accident (crash). Though as the traffic increases, they change these to full signalised intersections.
I feel the biggest problem run into with traffic lights, is players let the game keep the cycles far to short to REALLY give them a chance to work as desired. The areas approaching these intersections need to be well planned, otherwise you're going to have to cause some disruptions to established areas to fix them later.
IRl long cycles are quite frustraing, especially if you are waiting for a turn with short window. And, frankly speaking, if you need to squeeze percents by fine-tuning traffic lights, you likely have bigger problems.
@@permeakra But, we aren't talking IRL. People don't give themselves the space for expandability within many areas, especially at the beginning. So, they're afraid of expanding a road to lose businesses etc... and losing population, afraid that it won't rebound. This video is a great example of road planning, lane mathematics and management. I have to agree with him, in that Roundabouts are overrated. They're fine for collectors and secondary. But arterial and highway either need far too big of a round about with limited input lanes.. or high volume lights. There will never be a perfect solution to any of them. Frankly, anything above 60% is pretty good.
@@717dash_cam 1-lane roundabounds are fine, 2-lane sometimes work - but you need to make them really big. Never disagreed with that. Point is, at some point traffic problems are not solvable by optimizing locally. The game represents that part of RL quite fairly =).
I found this very interesting. It really comes down to how much time one wants to spend evaluating the traffic entering the intersection. In a live game, if there were let's say a large industrial complex feeding the south arterial one would have to evaluate and modify the timing on the lights accordingly (so that not all of them are 15 and 25) and occasionally revisit the location to monitor that the traffic flow hasn't changed and thrown the previous settings into chaos. This is both entertaining and educational.
Finally someone who doesn’t put a roundabout everywhere where they have a traffic problem. As someone who also enjoys optimizing traffic signals in CS, one of my favorite scenarios is timing traffic signals on one-way couplets to create the “green wave” for the platoons, works great, and I haven’t seen anyone demonstrate it yet.
Finally somebody said it. Never understood the love of them in skylines, given so many of their real world advantages don't really matter that much (safety, and no need for power or maintenance of lights. Efficiency in low-medium traffic is still good though). We don't use uncontrolled roundabouts in high traffic areas even in the UK. Most of our large busy exchanges are roundabouts with lights controlling them, not least for the reasons you noticed. If you have lots of traffic flow in either NS or EW routes they will tend to 'lock', giving you very unbalanced flow. Turning left is extremely slow if there are no gaps in the traffic. Left turning traffic conflicts with everything, even left turning traffic from ahead (traffic lights can let opposite left turns through). In high traffic situations you need some system for letting people turn left, otherwise left turning traffic tails back and starts to mess up other junctions. Where roundabouts really shine is wherever you might use a multi way stop, as it achieves the same thing but avoids people stopping when there is nobody obstructing them. If you have one route that is used far more often than any other through the junction then you don't need to worry about balancing controls. That's great right up till it gets saturated. Roundabouts are a great default junction, because they have fantastic behaviour the majority of the time with very little effort. That doesn't mean they are the best performing junctions.
@@xenn4985 the times I've visited, everything about your cities is mostly about cars and driving, the amount of space you dedicate to psrking lots is astounding to me. The city i come from in the uk is around 250k people and is only 40km big, its just one of the things i noticed, hell even london isn't built around cars it has insane level of transport links. (then again uk has tiny houses compared to us and all are built of brick generally we don't do wooden prefabs or anything often) its not a dig.
Very interesting. I've tried using both in C:S. Initially, in my city, I had the entrance to the city a huge roundabout with traditional TM:PE settings for a roundabout. It had nonstop backups. I tried the same roundabout but with traffic lights at each end, timed them together and it worked okay, though at times the backups were worse than without lights. I then set up a four-way timed traffic light and it worked amazing. I do use timed traffic lights a lot in my city, probably more than I should. I also don't get the point of having 100% perfect traffic flow. I find backups in traffic cool to watch. They represent reality, and sometimes it challenges you to making amends while also keeping it real. Backups happen. Thanks for the video!
One time I was playing C:S and I was like "You know, wow, I could really quite easily recreate my entire city here in the game." And I did...and the traffic started backing up to the point it broke medical services, couldn't transport the dead, couldn't leave the city, couldn't enter the city. The way to fix it was by adding an additional lane in and out of the city on one of the highway connections. Instantly cleared it up all the traffic! I guess that's the problem when you focus all your industry in one part of the city and rely on highway connections to drive workers in with no available public transportation and a horrendous grid system.
People who seek perfect traffic flow are the kind of players who meticulously curate their cities like a bonzai tree. For me at least, I like to make the fictional world as great as possible for the fictional citizens. One element of that is good transit. 90% is the baseline but so far it dies at 60-70k for me.
I find that roundabouts work best for medium traffic density, and they can sometimes be useful for low traffic situations with three roads coming from odd angles. But, the absolute best way to avoid traffic back-ups is to diffuse traffic with multiple route options, and just use simple intersections. Also, pay attention to road hierarchy. Using roundabouts as a default intersection is, in my view, a bad idea. It takes up space, and simply organizing your road system will solve most problems.
I'm a roundabout addict in Cities Skylines, I've actually never used a traffic light before. You convinced me to give it a try, thanks for the tip on the timing settings!
Roundabouts have their place but are most certainly not the miracle they are portrayed to be at times. I use them but only at very specific intersection scenarios.
Here in the UK we know about roundabouts, your 3 lane roundabout before converting to lights was all set up wrong, traffic was changing lanes when they shouldn't making joining traffic give way. You need to use NODE lines to make them stay in the correct lane depending on where they are going. e.g. cars on the south side heading west should be on the INNER lane until they get to the north part, where they would switch to the middle lane. I saw cars on the left lane (which should be going west) actually turn off and head north. Cars in the middle lane can either go EAST or North, if they go north they SHOULD stay in the middle lane and exit on the left or middle lane on the north exit, but they cross over to the outside lane at the east junction forcing the cars coming in on the east (and heading north) to give way. Hope this makes sense, hard to explain really. google something like -- "UK 3 lane roundabout rules" but reverse it for your side of the road since we drive on the left.
Dutch Civil Engineer here. We do love our roundabouts.. but only where it is applicable. High density crossings with a lot of traffic from multiple directions will be signalized. They have a much higher throughput than roundabouts (if you time the lights correctly), at the cost of safety and often higher lifetime costs. Roundabouts have fewer (50%) accidents, and far fewer (75%) fatalities/serious injuries compared to regular crossings due to less difference in speed between vehicles/bikes/pedestrians and angles of entering the crossing.
I think roundabouts work best for traffic that unevenly comes from one direction and splits into a few side streets (example: one of your main entrances to an industrial area splits into a few side streets and if you use a light it tends to cause backups coming in, but if you use yield signs it also causes backups on the side streets) or on streets that get sporadic traffic (example: a few streets down from lighted intersections). In most cases more roads going to more spread out places in your city seem to clear traffic faster. Instead of only one way to get in and out of your busy area, do at least three going to completely different areas of the city.
I recreated this with the following changes: - Enable Advanced Vehicle AI: ON - Dynamic Lane Selection: 100% - Simulation Accuracy: Very High - All cases simulation run for 10 minutes: Case 1: Default timed traffic light - Traffic Flow: 54-59% Case 2: 3-25 second timed traffic light - Traffic Flow: 49-54% Case 3: 3 lane roundabout: - Traffic Flow: 43-47% Case 4: 4 lane roundabout: - Traffic Flow: 54-58% Case 5: 3 lane highway roundabout: - Traffic Flow: 66-69% Conclusion: In City: Skylines, 4 lane roundabouts and default timed traffic lights produce similar traffic flows. While using a highway produces the best results, it's the least realistic. (centripetal force would be pretty intense) Note: The issue with roundabout traffic not giving way is solved by turning the simulation accuracy up.
@@YUMBL One of their stats when you select them is "cars charged last week" or similar. It's not perfect, but it's good enough to see if there's enough difference to actually bother. Make sure to put them on the outgoing traffic only, so it's not affected by any tailback from the intersection under test. For the typical 3-lane highway, the large one-way booth (8-kiosk) can usually handle the full load. Using traffic manager to force the traffic to split up at the booth is helpful sometimes, as is turning on automated tool-booths (higher speed through the booth).
This is some excellent data. I'll have to try out this map myself to see if I can make roundabouts work. Two things I'd like to see; using node editor to embiggen entrances, smoothing out the curves to increase vehicle speed / reduce sharp turns, and setting up traffic lights on each roundabout entrance. Yeah, really. That's a pretty common setup in the UK as it prevents the roundabout backing up, though I wouldn't know how to set that up in TM:PE. Roundabouts with traffic lights are the go-to service interchange here.
Buy some squares and connect it all the way back at the interchange. Then use lane connectors near the intersection so theyve already picked their lanes.
The stoplight could actually be timed even better. You could set the light to trigger a shorter window for both ways to turn left, then both directions to go straight at the same time so you can clear N-S and E-W as the same time. Also if you add slip lanes to the traffic light, it would probably be the best of both worlds, and the most efficient.
Simultaneous protected lefts would be great. In fairness, the roundabout could be better optimized too. The public's recommendation to have two exit lanes here hurt efficiency because for whatever reason, you can see the cims are, even when turning right, entering the center lane and inhibiting the through-traffic. I agree though that for this configuration of heavy through-traffic the traffic volumes are reaching the limits of what a roundabout can do, and not offering any of its advantages.
I've actually used a few configurations for arterials that simply could not handle roundabouts - as you so aptly demonstrated, roundabouts can fail HARD in high traffic situations. 1) Mini-interchange, using overpasses and ramps. Think of a system interchange shrunk down tiny. The tinychanges can have their own problems, though, especially if there are any conflicts. 2) Timed traffic lights and slip lanes. These can be VERY effective, even more so than your test light. 3) Overpass bypasses. I measure the traffic flowing from different directions; if everyone, say, is trying to turn left and jamming the intersection, I'll put an elevated left turn in and signalize the ground level intersection. This is a specialty trick, and requires the Vanilla Overpass Project assets, but it can be AMAZINGLY effective if you have unequal traffic at a major intersection.
And at about 14:40 there's that dentist office waiting room feeling again. But on a serious note: I really really wish some of these traffic management mods would be made for Transport Fever 2. Because the traffic lights in that game only function to build heavy backups. And no matter what you do, no matter how many lanes a road has, only one is ever used.
Love the experiment, but I think a lot of this is dependent on the type of traffic and the sizes of the roads. As you say this works for high throughput areas. If you are going for massive 7 or 8 lane roads that is highway grade arterial roads. Roundabouts will probably be fine for roads with a third of the traffic and no more than 4 to 5 lanes. I have seen those 12 lane roads on the workshop and figure that you could replace all of the highways on a map with those, and drop having any interchanges. BTW, any way to change the default numbers on the Timed Traffic lights. When setting them up it takes ages to fill in the numbers. Even with the copy function it is a pain.
For my building style (which is more on the American cost-saving side) I only use roundabouts where there is only a moderate amount of traffic (which they are best for IMO) I have plenty of space I know I won’t need, there is little or easily redirectable pedestrian traffic, and if there is industrial traffic that will make me have to change the dimensions of the roundabout. I always think to my self if a roundabout is really necessary when a traffic light or some signage will get the job done just fine so I only use roundabouts when I believe they are perfect for the situation I’m not against roundabouts I just don’t think they are the best traffic solutions to ever exist (at least within cities skylines) PS: great video it really shows how roundabouts in the game don’t work great with really heavy traffic
The king of intersections at it again haha. I will say from my own observations when driving here in the UK, the larger roundabouts tend to be traffic light controlled anyway. So perhaps the reasoning is more to do with the relative safety of roundabouts compared to 4 way stops rather than pure flow
i've subscribed to that map, and i'm gonna use it to test some stuff. for example, i'll try a different setup for the traffic lights. instead of letting cars from one direction go while cars from the other 3 directions have to wait, i'll try this: 1st phase: cars from the north AND the south are allowed to go straight 2nd phase: same for east-west instead of north-south 3rd phase: cars from the north and south are allowed to turn left 4th phase: same as 3 except east-west instead of north-south. and of course everyone is always allowed to turn right. pretty sure that this setup will increase traffic flow but i'm willing to be proven wrong.
Also if you have right turn only lanes then the adjacent direction can turn right while the other traffic is still going. I tend to do 4 cycles like that and leave 1 for pedestrians only. Traffic is not a thing any more. Tl:dr: timed traffic lights and micromanaging which lanes go where can have some extremely beneficial results.
After 3,756.5 hours of playing this game I’m glad someone is finally saying it. I ONLY use roundabout intersections at 1/2 asymmetrical roads or 1/1 roads in suburban neighborhoods. I believe in grids. Grids work. High density cities work avoiding using too many highways is the best bet for the vanilla gameplay start small build out organically and focus on walkability and bikes I avoid placing Stroads all together if possible. I was wondering if everyone is so afraid of Biffa 😂 that they have to play just like him.
You are absolutely correct, Yumbl. I had to switch out a lot of roundabouts for a 4-way lighted intersections because I've found roundabouts to be inefficient.
@@YUMBL Correct. Only on the biggest roads. No matter what I tried I could not get my roundabouts to flow in heavy-traffic conditions. I finally gave up, removed them, then added a 4-way timed-light...and voila!
This is what I’ve always thought. Every single bad intersection I’ve ever had was very easily solvable by using timed traffic lights: no need for the removal of buildings and it always seems to work much better than roundabouts! The most traffic-heavy areas of my city all have custom set ups of traffic lights that conform to the needs of the specific intersections (like longer green lights on the main road, for example). And my traffic flow rarely ever dips below 85%. The city is at ~340k pop.!
😂 YES!!! Thank you for showing all your work and handling the oft-used arguments. I get European city builders complaining that I use too many intersections and that I should use roundabouts instead of traffic lights ALL. THE. TIME. I love this test too because you used what I would call the _least_ efficient traffic light setup (one direction at a time + nonconflicting right) and it _still_ blew up a moderately efficient roundabout. Thank you 😁 and of you really want to make some heads explode, show them a CFI or even a quadrant intersection 😜
@@YUMBL oh I was laughing my head off just like you! 😂 Besides the CFI and the quadrant, it would be fun to see the roundabout signalized. I think a signalized roundabout would perform MUCH better because the problem created with saturated traffic density like you have here is that only one entire direction can flow at a time, rendering multilane roundabouts pretty much useless, because three directions always have to stop anyway, and they don’t get a very long window of continuous flow. Therefore signalizing the roundabout would drastically improve flow, as one direction would actually get some momentum going...just like the timed traffic light. This all reveals the _real_ reasons for roundabouts-it’s not all about continuous flow, because obviously with high enough traffic density there is no continuous flow. If you want continuous flow for high traffic density, as you pointed out, an interchange is the way to go.
Someone poi ted out in a comment that roundabouts are bad where flow is too little (overkill) or too much (it locks up) but is great everywhere in between. I would tend to agree, space allowing. But the “space allowing” part can’t be understated.
Awesome video! This generated a ton of discussing and reading the comments was enjoyable. It was odd to me that most traffic wanted to go straight; I don’t understand the game’s rng and why it would prefer intercity routes to be fully across the map
tbh I think this is not so different from real life. Roads are built along important routes, meaning traffic will want to go straight (stay "en route") most of the time when hitting an intersection or interchange. As infrastructure continues to develop and more destinations spring up, the existing road may be sufficient to act as a route between these new places, so you get additional right or left turning traffic from this. But if that left or right turning traffic becomes too much to handle, you can create a bypass road along this route, splitting these two important routes onto separate roads so they don't intersect anymore. But that just means traffic will want to go straight again. This is all because of a basic property of geometry. Let's consider the location of an interchange and call it A. Then let's pick two destinations so that to get between them via A you need to turn left or right. These are B and C. Going from B to C via A can _never_ be the shortest possible route from B to C. It _may_ be the shortest route _currently available_, but it may also not be. On the other hand, if you're going straight across an intersection, this theoretical "idealness" of your route is not impacted. Other intersections, or even bends in the road, will likely do so, but the issue there is not with the fact that you've used the intersection. TL;DR: turning has more potential to make a route longer than it needs to be than going straight, so it's likely that hypothetical turning traffic will be able to find a better route, removing them from the intersection entirely.
I've used a couple roundabouts to replace lights, but in almost every case I've had to remove them and upgrade to something better. If a 4/2 asymmetrical intersection with timed lights won't keep up, chances are the roundabout won't either. I've upgraded a lot of my major intersections to simplified CFIs, and although they take quite a bit of setup with lane arrows etc, they do move a lot more cars. Partly that's due to just having more lanes available, and partly due to being a 2-phase traffic light.
Where I live, we have a roundabout that is managed by traffic light, I think the reason for it is because there is a tram track that is going straight through the roundabout and to inusre safety they've added traffic light.
I have similar experiences. I've followed suggestions such as lowering the roundabout speed "to let more cars in" but all that seems to do is reduce throughput. I've also made it bigger, added slip lane right turns, etc. but stuff like that just makes it take up more room and eventually approaching the size and complexity of a proper interchange. Meanwhile the timed intersections move a lot of traffic in a small amount of space. Honorable mention goes to raised or lowered roundabout functioning as an arterial exit, but that's still medium duty in my opinion. I think roundabouts can offer utility in suburban settings, like a low density neighborhood transitioning to a strip mall area. Otherwise I think the big benefit of roundabouts is that they're probably the best option when Traffic Manager isn't available. The vanilla lights are absolute trash and, in my opinion, worse than completely uncontrolled intersections. Due to lack of lane control, many common heavy intersection configurations aren't viable in vanilla C:S. Personally, I set the traffic light minimum time very low, usually one second but up to four, and use the flow control slider to control traffic. This way I don't need to be concerned about dead periods where nothing is moving when traffic is asymmetrical, which is probably usually the case. The ideal configuration is the one with the fewest light cycles since you lose throughput during light changes. As this video suggests, very long cycles typically moves the most traffic but the roads need to be configured in a way where the cars can queue. That is, it's not going to work well when there are intersections right next to major junctions like this. In those scenarios, the flow meter needs to be set more to the right for more frequent light changes. There are more options to handle pedestrian traffic with a timed intersection. Even under "auto" settings they tend to get in the way of cars less than when crossing the roundabout. They can be given their own light cycle, which is fun to watch. It's like having your own Shibuya crossings. Pedestrian overpasses or tunnels are options in either case, though.
Great video. This is something I suspected for a long time, too. Using timed lights vs roundabouts, in any configuration, really, shows that timed lights are always or almost always superior for high density traffic. I hope to see more in-depth and more scientific videos about intersections :) Maybe some mod to actually measure traffic flow?
Great experiment! My two remarks only due to my experience in real life as a driver in several european cities - Roundabouts work better when they have a number of lines equal to the max number of lines in the roads getting there, plus one. So in this experiment i would have tried also a 5-lines one way road for the circle. Maybe it's worth a try. - Roundabouts work MUCH BETTER when they are at intersection of roads with different density. When you have (such in this experiment) two high-density roads traffic lights are better, while when one of the roads has a lower traffic flow the higher density one takes advandages of the lower. This does not happen with traffic lights. Of course these remarks have to cope with the CS traffic AI engine, which may be (very) different from real life.
You've convinced me that roundabouts don't work as well as traffic lights for high density (in cities skylines), all though I'm still going to try to make it work with this interchange testing map. Roundabouts are still my choice for lower density intersections, especially when I have more then 4 streets intersecting at once.
I tend to agree that in this particular instance that a roundabout doesn’t hold up well. However I don’t think a roundabout would be built in this scenario with heavy traffic going in all directions. The roundabout works well when you have a singular dominant flow of traffic that you want to prioritise without holding it up with (even short) light phases
I ran into this problem a while back, so I made a really compact full clover for collectors (the biggest roads I tend to use outside of highways). If you set up traffic manager correctly it flows almost completely freely for most traffic conditions and takes up about the same space as the roundabouts I tend to make. I'd be curious to see what a magic roundabout would look like here, but that would be even bigger.
I'm a dedicated Biffa fan, so I LOVE roundabouts. But this was a fascinating video, and a very compelling demonstration. I think you might get even better results by altering the timing of the lights and playing with some of the advanced options ("more waiting than driving", etc.).
Agree 100%. I hardly ever use roundabouts anymore. I only use them as an aesthetic choice when I know the traffic isn't going to be too bad. I use tm:pe simulation accuracy at very high and the dynamic AI lane selection at 70 and the timed lights are far more efficient. Medium traffic on one pair starts to choke the traffic on other street pairs and heavy traffic just kills the whole thing, but a well set up traffic light keeps everything under control. Just have to tweak the light to find the right timings sometimes.
This was extremely interesting! I never understood the fixation with them and have never seen them effectively used in heavy density. Even in real world they are a pain to navigate as you run into the proverbial "who's on first?" routine.
one thing that always gets me about multi-lane roundabouts is that if you have to turn left on them, you have to cross 2(+) lanes to get in to your lane, which can be close to impossible sometimes. so that can easily cause massive backups, with the traffic lights you just wait for your turn and empty the entire lane all at once. so as nice as turbo roundabouts are, i'd never really go for one with more than 2 lanes, if you need more, use multi-lane traffic lights like yumbl did, or just make it a highway interchange
yumbl: conclusively roundabouts are not the best option for high density roads in cities skylines commenters: I CAN'T BELIEVE YOU HAVE DISPARAGED ROUNDABOUTS, THEY WORK WELL IN LOWER DENSITY CONFIGURATIONS, THIS TEST DOESN'T ADDRESS MY PARTICULAR USE CASE would be dope if people actually watched the whole video before feeling the need to defend their beloved roundabouts
@10:07 something isn't right there. The cars on the roundabout stop to give way to quite a few cars entering the round about and they shouldn't do. This has a knock on effect blocking other exits. Maybe it is the AI level?
@@thebestspork This plus as seen in some of the footage with the timed traffic lights, some of the vehicles jump the lights and attempt to cross traffic before it clears. Simulation accuracy needs to be high or very high if we want to be as realistic as possible when comparing junctions.
@@YUMBL So it appears it isn't the AI setting that does this, the Simulation accuracy seems to control how well the ai responds to the yields. With it set to very high, they will stop on yields as needed 95% of the time. That doesn't solve the traffic flow though, the timed light is still better even with the yields working
This please. Especially if there is some sort of automated way to generate intersection statistics, like average speed, or cars per second, average waiting time, or something. It also would be interesting to see a (super)turbo roundabout tested.
This is why in Europe most roundabouts are on single maximum two lane roads. The main benefit of reduced collisions is also negated when more lanes are added. 4/8 lane roads are not very common and would be grid separated anyways, there are reasons why the US has different systems in place that Europe. Stroads and lack of alternatives to the car (sometimes caused by planing deficits/ huge suburban sprawl) are way bigger problems and while the roundabout is a great invention and useful for smaller roads (when implemented correctly) it is not the tool to replace all traffic lights, which is also the reason why we still have them in Europe as well ;D
So satisfying watching the timed traffic lights and seeing all the lanes being used. I've always preferred them to roundabouts in the game since they take up no extra space.
That's pretty close to scientific proof, very well done. You could slightly boost it by telling straight lanes to ignore the very right one, leaving it for right turn only. Then modify lights to right turn always green or "allow right turn in Red" in TMPE Options. Single-Node- Sliplane However, I still love watching traffic at roundabouts, not stopping at lights. For eyecandy I'd still opt for the roundabouts. High appreciation for your kind way of presenting, thanks
_Biffa will remember that_ Yeah I've reached the same conclusion. I still think they have good uses though but they're by far not a catch all solution. Edit: also thanks for the test map, I was curious how you did your testing, I'll definitely be getting this.
As with every type of road junction they are useful in the right situations. Once you reach a certain density of traffic they do create traffic backups, so a lot of very busy roundabouts here in the UK have had traffic lights installed on them to help keep the traffic flow even. One of the main advantages of them IRL is the safety aspect, which is obviously not something that needs to be considered for the simulated traffic in C:S.
FINALLY!! Someone who doesnt throw friggin doughnuts at every traffic issue whether it makes sense or not (and in many it doesnt). One main excuse is safety...but this is a game...plus, you cant have fast moving, high volume traffic 3-4 lanes wide "controlling itself" to yield, merge, shift lanes in circle, get out, etc properly or efficiently or there would be a pile up every 5 minutes. Seriously, people are stupid and dont pay attention; they crash regularly on the straight highway trying to change lanes and more often at on\off ramps, bringing traffic to a hault for miles...yet you think they could handle a roundabout like this? Lol, thats hilarious. Yeah they work in cases, but so does many other things. To me its a theme thing, not a best function thing...but everybody for some reason doing CS videos started using them everywhere, maybe the lazy way out? I cringe even hearing the word as ive seen many ppl on here build them religiously, got to the point i stopped watching builds and especially traffic fixes because i already knew what was coming. Thank you for giving me hope again!! Lol... Anyway love ur vids dude, you do nice work
Interesting argument. With traffic flow, I tend to do a DDI or stacked roundabout. Though when I do make roundabouts, I normally don't do a 90-degree input. Usually brace the roundabout with the inputs at the 90-degrees, but then add lanes to those inputs at about 45-degrees from them. It's a little bigger, due to needing 9 extra roads to reach their destination, but it seems to work. Though I do have spots on a map where that didn't work.
As a Texan who travels this big state it is hard to find round abouts so I am a little bias about signaled intersections. However, Texas has had it's many shares of unique hybrids that are part roundabout, part signaled, and part overpass. It's really interesting how TXDOT really builds their roads. Love the videos thank you for them and keep making them!
Sorry, disagree with this video entirely, you can't make a custom intersection (Which worked very well), and compare it to a basic roundabout. The thing about roundabouts is, the busier they are, the larger they have to be. If the roundabout was bigger, had proper exits and entrances and slip roads, roundabout always wins. I had a nightmare city once, with 3 main intersections on the main road. I changed 2 of those to roundabouts (pretty big, proper slip lanes) and my traffic was cured almost instantly. Always love your vids, but I just don't happen to agree with this one.
@@YUMBL to be honest, I don’t see what is flippant about it. I happen to disagree also, since roundabouts are pretty much a solution on multiple occasions. It does need sliplanes, vehicle AI upped and good speeds on entering and on the roundabout itself. Setting a nicely managed timed light with separate lanes versus a regular roundabout is not an equal footing. Also actual turbo roundabouts are a different beast entirely.
@@YUMBL not to be pedantic but he wasn’t being disrespectful. One thing I did notice on the intersection is that people are actually waiting a long time. Although the roundabout has one lane on two sides stretching out, it would be interesting to see what the actual throughput is on both. I’d reckon it is not all that different, given the fact that the actual backup doesn’t seem to keep expanding.
In my current city I have replaced most of my roundabouts along the arterials with timed trafiic lights since the roundabouts always seemed to cause more backups. So I agree with your point. However, where I still have roundabouts I make sure that the roads connecting to the ring come in at an angle (not 90 degrees). That seems to greatly improve the flow and it would be interesting to see a new comparison where both the traffic lights and the roundabout are fully optimized.
On mainland Europe, the most common kind of roundabout is a single lane roundabout, possibly with sliplanes, and often three-way rather than four-way in the industrial / commercial / office areas that are often found between large roads and cities. There they work nicely. For anything heavier, you will find interchanges, where there is space, or intersections.
In Argentina we don't turn left on avenues or highways. It's not a thing! You have to turn 3 rights and it's totally fine. Well, we do have designated left turns but they are very circumstantial.
So you're saying a roundabout doesn't work for a junction it wasn't designed for, big shocker. By making this one junction the only connection between highways it's essentially a system interchange. A roundabout is not a complete system interchange, it cannot cope with all that traffic. It can however be part of an interchange if you grade seperate the through movements and use a roundabout for left & right turns only. This video is an unfair experiment because you are trying to make a roundabout do something it simply cannot do. The function of a roundabout isn't for dealing with a large volume of traffic. The function of a roundabout is to increase safety over a normal junction with traffic lights.
Might not be a big shocker for you or I, but seems to be news to quite a lot of people. The setup is quite artificial, as all experiments are, but it is entirely possible to set up worse conditions by accident, and this is a good demonstration of the limits of roundabouts. The whole point of the video is that it highlights what roundabouts cannot do. The challenge is not insulting Biffa at the same time, which is I think why it's tone is so scientific.
At this point it's really just logic - above a certain traffic density, you run into issues with traffic in the roundabout having to stop when a vehicle decides to enter the roundabout, which completely seizes everything up. I've had situations where roundabouts have completely gridlocked on me, and putting in either a well-timed light or a small interchange was the solution.
I just banned cars in the city, and residents get somewhere exclusively by public transport. There are almost no traffic jams, only on the end sometimes, but if you build the final ones correctly, there will be no traffic jams. Public transport top!
Bro I'm just shocked, I never even thought of using traffic lights since lots of people say that they are bad in the game. I've always wondered why there are mods for traffic lights since they are bad, you really changed my mind.
@@YUMBL I remember that biffa always says in his fixing cities series that they are bad and he always removes them. He only uses them when is the last option. Also in his vanilla 2021 city he never uses them aside from the main road he build in the middle because he doesn't have traffic manager. If he had it he would just give priority to the main road and make everyone else yield.
Hello. European traffic engineer here. Why do you have roundabout exit setting so "unequal"? You are leaving into 3 lane road but only have 2 lines exiting the roundabout. Also for such a high traffic scenario, you would choose "turbo roundabout" (don't know the exact translation) where entering lines form new lines on the roundabout (no right of way issues) and exiting lines end at the point of exit (again no right of way issue). This seems to me to be a highly optimized light-controlled intersection against a very basic variant of a roundabout, in which the roundabout will certainly lose (See Matthew Wong's comment for further analysis).
Please feel free to show me if that type of setup works. It seems impossible to have three lanes exiting safely as traffic would have to cross over each other. Also, the light was awful. It would be much more efficient if it had lefts going at the same time to shorten the cycles. Strange to me that a traffic engineer didn’t notice that.
After trying out RABs throughout my city, and YES I configured them properly with the right tool, I figured out regular intersections configured properly were much much better than RABs!
Your findings have been reproduced by scientists. In France roundabouts are everywhere, in Germany planners are fighting for the crossing with lights: so studies were made that do prove that under heavy load lights are better. Roundabouts can more easily adapt to dynamically varying loads and are better at low loads. Personally I totally love roundabouts. In southern France they are at all entrances to villages and serve as an unobtrusive speed damper. My frustration level is much lower when I'm in a continuous slow flow rather than intermittent stops. In recent years my - old - home region has been plastered with roundabouts and I barely recognize the roads anymore but driving is so much more fun / less annoying that before.
Agreed on all points! Roundabouts are excellent in many spots, and take up a lot of space, and slow traffic (many times in a good way), and break down with enough traffic.
I have built many, many, many cities since C:S was released. I've used traffic lights and I've used roundabouts. There was a series of cities where I overused roundabouts (it just so happens to coincide when I started to watch Biffa's channel). Then I found Lee Hawkins and I've basically abandoned, mostly, the use of roundabouts and have gone with the many connections theory that helps to spread out traffic. It's amazing how well that approach works. You'd think an intersection, even a four-way, every 12 units would cause backups. But it actually doesn't. What causes backups is if I make that a priority road using yield signs. It's unreal (and yes, I use TM:PE) It seems to me that roundabouts could come in handy in specific conditions where you want to slow down traffic a bit. Maybe the transition from one neighborhood to another. I know in Arizona, in the Sedona area, they have multiple roundabouts (though they don't actually call them roundabouts) on one of the major roads. it helps to slow down the traffic. I've read through some of the comments and I would love to see a counter video from Biffa. I love both of your channels. You both have unique approaches to the game and I'd like to think I've adapted my own playing style to take into account what you guys do. As a result, I'm a better player and my cities are better than ever. Throw in ideas from Lee Hawkins and I've got some awesome cities (not to mention CPP, as well). This was very informative. Nice job Yumbl. I think you need to be invited to the next season of 5 Builders, 1 City.
@@YUMBL It doesn't help much that one of the traffic tips offered during a game load (if you are not using the Loading Screen Mod) is to create a roundabout when you have heavy traffic. That could very well be where players get the idea to "overuse" roundabouts.
Love this example of how roundabouts aren't meant to be used on very high capacity/throughput roads. Roundabouts funcion most optimally in areas where you want traffic calming and an "equal priority" with a large and smaller road.
Well I've lived in Dubai for a good while of my life,.. and their traffic design has always been: -local roads use roundabouts -collector roads uses intersections -'highways' are always over head passes. And I have highways in quotation marks because most of their roads are 100+ km/h and are considered a highway.. that's why u see some really complicated highway systems in pictures of it xD But supporting your hypothesis, and also the way I've been integrating it within my cities, intersections provide better flow than roundabouts for high density traffic.
Hi I watched some of your roundabout videos they are really interesting I live some where that is really crowded place and roundabouts are every where So much traffic no road management there is no collector roads and residential and commercial is a nightmare how they managed to spared it Just watching your videos gives me so much ideas you know Simulation is a really great way to apply things before making a thing
Nice video, but I'm afraid that without a mod that counts how many vehicles have passed node with a given amount of time results will be widely disputed. With that flow setup I'd say that the difference is the same that we have in the current. With roundabouts we have direct current - traffic will be more less stable. With the traffic interchange you will have alternating current situation. The tail will be raising and falling.
The roundabout tails were trending longer and longer with time. As per my hypothesis though, are you suggesting that roundabouts ARE the best option on high density roads in cities skylines?
@@YUMBL No, you cannot say that without auditing the numbers. I'm just pointing out both could have different repercusion to network system. For example intersection could be better when near buildings that suddenly generate huge influx of vehicles. Roundabouds could be better in places where there are neither of these. But this should be tested in different environment.
What could be done is let the intersections run, select the last car in line, and see how long it takes them to cross the intersection. I see the success of a junction as how long (short) it keeps people waiting.
Gotta appreciate the effort to actually test this ! But I would like to add that idk for the us, but in France 50 m diameter for a roundabout is quite small. It’s what most light traffic roundabouts would be like. Huge roundabout r usually more than 100 m in diameter (sometimes up to 300 m). And for traffic lights 15 - 25 cities Skylines time units is quite long (and would be in comparison a long time for a traffic light in France). Still appreciate that you actually took the effort to test this.
Roundabouts are a good intersection for medium traffic or asymmetric traffic. Too little traffic and they dont really offer anything over stop signs, and they break down with too much traffic because of human nature mostly. However they do work good in merging a medium density or high speed road with smaller roads, as they give joining traffic a bigger opportunity to get in, and make left turns almost trivial. Roundabouts are the best overpass free uncontrolled intersections, however at higher or highway density, traffic lights and bridges show their might.
I wonder what both would be like. Timed lights on a roundabout. I can't test it myself but I really would like to see the results. Very interesting video, man. Thank you.
One of the biggest misconceptions with roundabouts is that they're better for traffic at _any_ density. In fact, roundabouts are best for the vast majority of situations, but only in the gap between "almost no traffic" and "way too much traffic". If there is only one vehicle interacting with an intersection at a time, 4-way yield is most efficient, since vehicles can just keep driving through without stopping or even slowing down. If there is a massive amount of traffic, the cars trying to enter the roundabout take up more space than the ones already moving, and can often slow down the cars already in the roundabout. That, or they have to wait for a large enough gap to enter. In a well-managed timed traffic light, intersection time is only "wasted" for a short period of time while one phase gets a yellow light, until the next phase is at full speed. The longer a particular phase is, the more efficient the intersection is, as long as there is 100% traffic flow through the intersection during any given phase. I'm kind of surprised you didn't test intersections using the other common phase patterns. The most common pattern I've seen involves opposing lefts getting the green, along with the complementary right turns, followed by opposing straights with complimentary rights, then alternating with the perpendicular directions of traffic. This can optionally be added on to with an effective yield for left turns during the associated straights phase (though this is often not allowed if it would be overly unsafe for that intersection, as is the case with double left turn lanes). This particular pattern is better when it can allow more simultaneous paths of traffic through the intersection. In your example, you had one left, two straight, one right lane getting the green, along with a single complimentary right turn lane starting from the entry point cw from the side getting the green. That is a total of 5 lanes of simultaneous traffic plus 2 yields. Instead, you could be getting 6 lanes during the straights phase (two straight in each direction, plus safe right turns), plus 4 yields (both associated lefts, and the remaining rights), and 4 lanes during the lefts phase (opposing lefts and complimentary rights), with 2 yields (the remaining rights). If all lanes are getting equal use and the phases are equal lengths, it would be the same in either case, but there are many cases that benefit one over the other. Either way, great video!
Thank you! The light is nearly default and easily set up. I wanted to offer a baseline of throughput for the light that anyone can replicate with ease. An optimized light (cycles, turn lanes, etc) DECIMATES a roundabout at high traffic volume.
A problem with both Traffic Manager and the vanilla lights is you can't tell them "green but yield on lefts". You might be able to fudge it with the advanced Traffic Manager conditionals I've never seen anyone use, but the core logic isn't there. As a result, round robin signaling tends to dominate.
Thank you all for the interest in this video! The hypothesis presented is supported by real world data as well.
Those who would like to prove the traffic engineering community wrong now have the control environment to show it! I appreciate your comments, but I really look forward to all of your thoughtful presentations :)
I'm curious about your traffic light setups. You set them up to be "only one cardinal at a time" but I wonder what would happen if you split up the 'straight through' traffic and the 'make a turn' traffic. so leftright for a while, updown for a while and then right/left/right/left and left/right/left/right (if you know what I mean).
I see that type of light configuration a lot in my local city, where it allows for seemingly more throughput as a lot more traffic tends to want to just go straight and there's less traffic volume making turns. So it's set up so that the straight through phases are prioritized and last longer.
It would be interesting seeing a video about different traffic light phase setups, depending on the traffic volumes. (Hell, I suppose there's even an algorithm you could run over it if you knew the makeup of the traffic)
The light can be much more optimal. For sure
@@YUMBL I agree with your conclusions. That said - something to think about. In the UK, a high traffic, high road count, high lane count roundabout like that would not be implemented like that. First there will be traffic lights. Secondly, lanes will always tend towards the outside - so you get into the correct lane for your exit and it works it's way outward so you are in one of the two outside lanes when you need to exit. That's how they get their large throughput.
Thank you! I just thought CS players deserve to know as well.
@@YUMBL Yes then it works even better when you set them up manually. ua-cam.com/video/6mHPgjhPCE0/v-deo.html
Hello. Traffic engineer here. The magical (potentially frustrating) thing about intersections is that there is a lot of hidden complexity. While it may seem a simple case of two roads worth of traffic intersecting, this is incorrect. The efficiency of traffic flow through the intersection depends on many hidden variables that require a lot of thought both in real life and in game.
In this case, the traffic lights are vastly optimal compared to a roundabout for probably multiple reasons, the most pressing as far as I can tell being the ultimate destination of cars passing through that intersection. For some reason, perhaps an unexpected result of the setup, it is evident from the traffic light time lapses in this video that the vast majority of cars are passing straight through the intersection as opposed to left or right. This kind of intersection greatly favours the traffic light. From a mathematical point of view, traffic lights benefit from very high flow from individual streams one at a time whereas roundabouts service multiple streams simultaneously at a lesser flow. Keeping this in mind, it makes sense that a traffic light would work better here since almost all the traffic has to cross the path of another stream. Roundabouts are much more suited to balanced directional traffic where the ratio between left, right and straight turning is closer (In actuality a perfect roundabout would have every car go to the right as then there would be zero conflict but that would defeat the entire point of having an intersection).
This isn't a perfect analysis, indeed such a thing is impossible without extensive computer simulation, but I just wanted to highlight that I certainly think there are situations where a roundabout may come closer to or even trump a traffic light in a high density traffic scenario. Although you are correct in that people are very "passionate" about roundabouts when they are certainly not the solution to every traffic scenario as some people seem to think.
Very balanced response! Thank you. I have yet to see a spot where a big roundabout beats a light in a high density situation though. They just seem to break down earlier consistently. I havent found a source that confirms that either. The light seems to maintain flow due to its versatility when traffic starts stacking in a way that roundabouts cannot.
Within the roundabouts threshold it thrives. Space allowing you to build it in the first place. Above that and its backup city. Then countries seem to add lights to the roundabout.
i definitely see your point...but unless a city is designed with no road hierarchy, most of the traffic IS and SHOULD be traveling straight.
@@YUMBL We do have Roundabouts in Australia where the side roads to the roundabout have traffic lights to allow the main roads to have a better chance of clearing the peak hour traffic. Then the main road stop and allow the side roads to clear. The main through road to the roundabout might have 2 or 3 lanes, while the side or local road has 1 lane. These lights are only activated during peak hour traffic times. It more like a hold back to avoid a frustrated motorist on the side road waiting 10 minutes to try to cross the main road peak hour traffic from trying to barrel through causing a accident (crash). Though as the traffic increases, they change these to full signalised intersections.
instead of ‘dealing’ with traffic, maybe reducing car trips would have a bigger impact on throughput than either a light or a roundabout-
we should de-incentivise car travel instead of paving over cites with asphalt to cater to them-
a generation of ‘urbanism’ that panders to motorists has gutted American cities, leaving us with free parking and stroads. It’s terrifying that terms like ‘walkability’ need to exist, what a deep hole we’ve dug for ourselves.
Now this I HAVE to watch!!! Edit: Interesting video. Question: did you turn on the TM:PE Traffic AI at all as watching the roundabout with all the "not really giving way" that kept happening I'm not so sure it was on then?
🤣🤣🤣
#SaveTheRoundAbout
I'm with you, @biffa... I know your way of setting up roundabouts, and I agree with it, but @yumbl makes a good point as wel, had the same experience... both have a use and place :)
@Biffa Plays Indie Games They all had yields, yes. By shift+ctl clicking with the yield its sets the whole thing up. I did it in the video.
@@YUMBL No I saw that, I mean in the TM:PE settings menu you can turn on the Advanced Vehicle AI. With this the game can cope better with a lot of things, particularly these alien builds we love so much, called roundabouts and the yield signs added with TM:PE. Without it the game seems to work better with traffic lights, which are a part of the game like stop signs. But with yield signs the game tends to need the Advanced Vehicle AI to help them get how they should work. I normally go for around the 70% mark :-)
I've done a research paper for university on roundabouts as a civil engineering student and my conclusion was that roundabouts are more effective in areas that have stop signs (or lower traffic volumes) rather than traffic signals (much higher traffic volumes). Arterial roads wouldn't benefit much from roundabouts as the volume of traffic is immense. Collectors and local roads have a much better benefit with roundabouts as the traffic isn't as demanding. While this video is a great example of how effective traffic lights can be, it wasn't optimized to the fullest extent as it appeared the left turning traffic was far fewer than through traffic. Maybe setting up a protected left only for a minimum of 5 seconds and then through traffic only for your times would improve the efficiency of that intersection even more.
All entirely true. I wanted the light to be easy to set up as most of the community swears by roundabouts. A good light will decimate the best roundabout.
Now a lighted roundabout…
@@YUMBL my research paper didn't include lighted roundabouts lol!
Yea. Once you add a light most of the charm and appeal of the modern roundabout disappears. The reasons people like it and such. Still probably safer than a regular intersection, but large. Efficient, but at what cost?
@@jacobgathman289 We do have Roundabouts in Australia where the side roads to the roundabout have traffic lights to allow the main roads to have a better chance of clearing the peak hour traffic. Then the main road stop and allow the side roads to clear. The main through road to the roundabout might have 2 or 3 lanes, while the side or local road has 1 lane. These lights are only activated during peak hour traffic times. It more like a hold back to avoid a frustrated motorist on the side road waiting 10 minutes to try to cross the main road peak hour traffic from trying to barrel through causing a accident (crash). Though as the traffic increases, they change these to full signalised intersections.
Can you provide said study? Urbanist im formation here 🙋♂️
I feel the biggest problem run into with traffic lights, is players let the game keep the cycles far to short to REALLY give them a chance to work as desired. The areas approaching these intersections need to be well planned, otherwise you're going to have to cause some disruptions to established areas to fix them later.
And then those roundabouts end up like this: ua-cam.com/video/N0HoqjxfvJ4/v-deo.html
IRl long cycles are quite frustraing, especially if you are waiting for a turn with short window. And, frankly speaking, if you need to squeeze percents by fine-tuning traffic lights, you likely have bigger problems.
25 seconds is short compared to many actual lights
@@permeakra But, we aren't talking IRL. People don't give themselves the space for expandability within many areas, especially at the beginning. So, they're afraid of expanding a road to lose businesses etc... and losing population, afraid that it won't rebound. This video is a great example of road planning, lane mathematics and management. I have to agree with him, in that Roundabouts are overrated. They're fine for collectors and secondary. But arterial and highway either need far too big of a round about with limited input lanes.. or high volume lights. There will never be a perfect solution to any of them. Frankly, anything above 60% is pretty good.
@@717dash_cam 1-lane roundabounds are fine, 2-lane sometimes work - but you need to make them really big. Never disagreed with that. Point is, at some point traffic problems are not solvable by optimizing locally. The game represents that part of RL quite fairly =).
I found this very interesting. It really comes down to how much time one wants to spend evaluating the traffic entering the intersection. In a live game, if there were let's say a large industrial complex feeding the south arterial one would have to evaluate and modify the timing on the lights accordingly (so that not all of them are 15 and 25) and occasionally revisit the location to monitor that the traffic flow hasn't changed and thrown the previous settings into chaos. This is both entertaining and educational.
Integration with real time would be interesting...
Finally someone who doesn’t put a roundabout everywhere where they have a traffic problem. As someone who also enjoys optimizing traffic signals in CS, one of my favorite scenarios is timing traffic signals on one-way couplets to create the “green wave” for the platoons, works great, and I haven’t seen anyone demonstrate it yet.
Thank you! One day i’ll master the green wave. Just tinkering til then ;)
Finally somebody said it. Never understood the love of them in skylines, given so many of their real world advantages don't really matter that much (safety, and no need for power or maintenance of lights. Efficiency in low-medium traffic is still good though). We don't use uncontrolled roundabouts in high traffic areas even in the UK. Most of our large busy exchanges are roundabouts with lights controlling them, not least for the reasons you noticed. If you have lots of traffic flow in either NS or EW routes they will tend to 'lock', giving you very unbalanced flow. Turning left is extremely slow if there are no gaps in the traffic. Left turning traffic conflicts with everything, even left turning traffic from ahead (traffic lights can let opposite left turns through). In high traffic situations you need some system for letting people turn left, otherwise left turning traffic tails back and starts to mess up other junctions.
Where roundabouts really shine is wherever you might use a multi way stop, as it achieves the same thing but avoids people stopping when there is nobody obstructing them. If you have one route that is used far more often than any other through the junction then you don't need to worry about balancing controls. That's great right up till it gets saturated. Roundabouts are a great default junction, because they have fantastic behaviour the majority of the time with very little effort. That doesn't mean they are the best performing junctions.
Its much better than a four way stop, no doubt. Collectors can work too, but not on big roads.
If you make them properly, they're better than any intersection
Absolutely untrue 🤣
@@xenn4985 I mean tbf, America could really do with building their cities not centered around cars so much.
@@xenn4985 the times I've visited, everything about your cities is mostly about cars and driving, the amount of space you dedicate to psrking lots is astounding to me. The city i come from in the uk is around 250k people and is only 40km big, its just one of the things i noticed, hell even london isn't built around cars it has insane level of transport links. (then again uk has tiny houses compared to us and all are built of brick generally we don't do wooden prefabs or anything often) its not a dig.
Very interesting. I've tried using both in C:S. Initially, in my city, I had the entrance to the city a huge roundabout with traditional TM:PE settings for a roundabout. It had nonstop backups. I tried the same roundabout but with traffic lights at each end, timed them together and it worked okay, though at times the backups were worse than without lights. I then set up a four-way timed traffic light and it worked amazing. I do use timed traffic lights a lot in my city, probably more than I should.
I also don't get the point of having 100% perfect traffic flow. I find backups in traffic cool to watch. They represent reality, and sometimes it challenges you to making amends while also keeping it real. Backups happen.
Thanks for the video!
Thanks for watching :)
One time I was playing C:S and I was like "You know, wow, I could really quite easily recreate my entire city here in the game."
And I did...and the traffic started backing up to the point it broke medical services, couldn't transport the dead, couldn't leave the city, couldn't enter the city.
The way to fix it was by adding an additional lane in and out of the city on one of the highway connections. Instantly cleared it up all the traffic!
I guess that's the problem when you focus all your industry in one part of the city and rely on highway connections to drive workers in with no available public transportation and a horrendous grid system.
People who seek perfect traffic flow are the kind of players who meticulously curate their cities like a bonzai tree. For me at least, I like to make the fictional world as great as possible for the fictional citizens. One element of that is good transit. 90% is the baseline but so far it dies at 60-70k for me.
I find that roundabouts work best for medium traffic density, and they can sometimes be useful for low traffic situations with three roads coming from odd angles. But, the absolute best way to avoid traffic back-ups is to diffuse traffic with multiple route options, and just use simple intersections. Also, pay attention to road hierarchy. Using roundabouts as a default intersection is, in my view, a bad idea. It takes up space, and simply organizing your road system will solve most problems.
This is true!
👍🏻 _Multiple direct routes diffuse traffic_
@@LeeHawkinsPhoto MMLT!
The best BEST way to diffuse traffic is to ban cars 😏 can't be traffic if there is no traffic.
I'm a roundabout addict in Cities Skylines, I've actually never used a traffic light before. You convinced me to give it a try, thanks for the tip on the timing settings!
Roundabouts have their place but are most certainly not the miracle they are portrayed to be at times. I use them but only at very specific intersection scenarios.
Bingo!
Maybe simulation and reality is not identical?
*in city skylines*
in which situations would placing a roundabout be beneficial?
Lower flow collector roads, space allowing. Roundabouts are excellent.
Here in the UK we know about roundabouts, your 3 lane roundabout before converting to lights was all set up wrong, traffic was changing lanes when they shouldn't making joining traffic give way. You need to use NODE lines to make them stay in the correct lane depending on where they are going.
e.g. cars on the south side heading west should be on the INNER lane until they get to the north part, where they would switch to the middle lane. I saw cars on the left lane (which should be going west) actually turn off and head north. Cars in the middle lane can either go EAST or North, if they go north they SHOULD stay in the middle lane and exit on the left or middle lane on the north exit, but they cross over to the outside lane at the east junction forcing the cars coming in on the east (and heading north) to give way.
Hope this makes sense, hard to explain really. google something like -- "UK 3 lane roundabout rules" but reverse it for your side of the road since we drive on the left.
Dutch Civil Engineer here. We do love our roundabouts.. but only where it is applicable. High density crossings with a lot of traffic from multiple directions will be signalized. They have a much higher throughput than roundabouts (if you time the lights correctly), at the cost of safety and often higher lifetime costs. Roundabouts have fewer (50%) accidents, and far fewer (75%) fatalities/serious injuries compared to regular crossings due to less difference in speed between vehicles/bikes/pedestrians and angles of entering the crossing.
I think roundabouts work best for traffic that unevenly comes from one direction and splits into a few side streets (example: one of your main entrances to an industrial area splits into a few side streets and if you use a light it tends to cause backups coming in, but if you use yield signs it also causes backups on the side streets) or on streets that get sporadic traffic (example: a few streets down from lighted intersections). In most cases more roads going to more spread out places in your city seem to clear traffic faster. Instead of only one way to get in and out of your busy area, do at least three going to completely different areas of the city.
I recreated this with the following changes:
- Enable Advanced Vehicle AI: ON
- Dynamic Lane Selection: 100%
- Simulation Accuracy: Very High
- All cases simulation run for 10 minutes:
Case 1: Default timed traffic light
- Traffic Flow: 54-59%
Case 2: 3-25 second timed traffic light
- Traffic Flow: 49-54%
Case 3: 3 lane roundabout:
- Traffic Flow: 43-47%
Case 4: 4 lane roundabout:
- Traffic Flow: 54-58%
Case 5: 3 lane highway roundabout:
- Traffic Flow: 66-69%
Conclusion: In City: Skylines, 4 lane roundabouts and default timed traffic lights produce similar traffic flows. While using a highway produces the best results, it's the least realistic. (centripetal force would be pretty intense)
Note: The issue with roundabout traffic not giving way is solved by turning the simulation accuracy up.
Cool experiment! The percentage is less helpful than seeing the cars imo, but counting vehicles would he ideal. I wish we had a counter
@@YUMBL Toll Booth = counter
Actually? How? I’ve never used them 🤣
@@YUMBL One of their stats when you select them is "cars charged last week" or similar. It's not perfect, but it's good enough to see if there's enough difference to actually bother. Make sure to put them on the outgoing traffic only, so it's not affected by any tailback from the intersection under test. For the typical 3-lane highway, the large one-way booth (8-kiosk) can usually handle the full load. Using traffic manager to force the traffic to split up at the booth is helpful sometimes, as is turning on automated tool-booths (higher speed through the booth).
This is some excellent data. I'll have to try out this map myself to see if I can make roundabouts work.
Two things I'd like to see; using node editor to embiggen entrances, smoothing out the curves to increase vehicle speed / reduce sharp turns, and setting up traffic lights on each roundabout entrance. Yeah, really. That's a pretty common setup in the UK as it prevents the roundabout backing up, though I wouldn't know how to set that up in TM:PE. Roundabouts with traffic lights are the go-to service interchange here.
Cromulent suggestions, sir.
Do it!!!
@@YUMBL okay fine jeez
also I love your single point partial cloverleaf, it works so well
Damn we have a ton those traffic light roundabouts here in India and they work unexpectedly well in CS
Buy some squares and connect it all the way back at the interchange. Then use lane connectors near the intersection so theyve already picked their lanes.
Finally someone has the courage to say what I've been thinking for ages now.
We love our roundabouts in CS. I just thought someone should acknowledge the limitations :)
The stoplight could actually be timed even better. You could set the light to trigger a shorter window for both ways to turn left, then both directions to go straight at the same time so you can clear N-S and E-W as the same time. Also if you add slip lanes to the traffic light, it would probably be the best of both worlds, and the most efficient.
Simultaneous protected lefts would be great. In fairness, the roundabout could be better optimized too. The public's recommendation to have two exit lanes here hurt efficiency because for whatever reason, you can see the cims are, even when turning right, entering the center lane and inhibiting the through-traffic. I agree though that for this configuration of heavy through-traffic the traffic volumes are reaching the limits of what a roundabout can do, and not offering any of its advantages.
I've actually used a few configurations for arterials that simply could not handle roundabouts - as you so aptly demonstrated, roundabouts can fail HARD in high traffic situations.
1) Mini-interchange, using overpasses and ramps. Think of a system interchange shrunk down tiny. The tinychanges can have their own problems, though, especially if there are any conflicts.
2) Timed traffic lights and slip lanes. These can be VERY effective, even more so than your test light.
3) Overpass bypasses. I measure the traffic flowing from different directions; if everyone, say, is trying to turn left and jamming the intersection, I'll put an elevated left turn in and signalize the ground level intersection. This is a specialty trick, and requires the Vanilla Overpass Project assets, but it can be AMAZINGLY effective if you have unequal traffic at a major intersection.
And at about 14:40 there's that dentist office waiting room feeling again.
But on a serious note: I really really wish some of these traffic management mods would be made for Transport Fever 2. Because the traffic lights in that game only function to build heavy backups. And no matter what you do, no matter how many lanes a road has, only one is ever used.
I just discovered this channel, high quality stuff. Keep going.
Thanks a lot :)
Brilliant content. Especially how you established the test conditions. That was great as it allows for making actual comparisons.
Thank you! I hope to see others attempting this :)
This video blew up pretty quickly for a Skylines game. Nice work. 🤘
Wish traffic manager was part of the base game
I've noticed this, too. A good lighted intersection is great
Love the experiment, but I think a lot of this is dependent on the type of traffic and the sizes of the roads. As you say this works for high throughput areas. If you are going for massive 7 or 8 lane roads that is highway grade arterial roads. Roundabouts will probably be fine for roads with a third of the traffic and no more than 4 to 5 lanes.
I have seen those 12 lane roads on the workshop and figure that you could replace all of the highways on a map with those, and drop having any interchanges.
BTW, any way to change the default numbers on the Timed Traffic lights. When setting them up it takes ages to fill in the numbers. Even with the copy function it is a pain.
Thank you! Idk if you can change the default numbers
Great experiment, well done video!
Thank you :)
For my building style (which is more on the American cost-saving side) I only use roundabouts where there is only a moderate amount of traffic (which they are best for IMO) I have plenty of space I know I won’t need, there is little or easily redirectable pedestrian traffic, and if there is industrial traffic that will make me have to change the dimensions of the roundabout.
I always think to my self if a roundabout is really necessary when a traffic light or some signage will get the job done just fine so I only use roundabouts when I believe they are perfect for the situation
I’m not against roundabouts I just don’t think they are the best traffic solutions to ever exist (at least within cities skylines)
PS: great video it really shows how roundabouts in the game don’t work great with really heavy traffic
The king of intersections at it again haha. I will say from my own observations when driving here in the UK, the larger roundabouts tend to be traffic light controlled anyway. So perhaps the reasoning is more to do with the relative safety of roundabouts compared to 4 way stops rather than pure flow
i've subscribed to that map, and i'm gonna use it to test some stuff. for example, i'll try a different setup for the traffic lights. instead of letting cars from one direction go while cars from the other 3 directions have to wait, i'll try this:
1st phase: cars from the north AND the south are allowed to go straight
2nd phase: same for east-west instead of north-south
3rd phase: cars from the north and south are allowed to turn left
4th phase: same as 3 except east-west instead of north-south.
and of course everyone is always allowed to turn right.
pretty sure that this setup will increase traffic flow but i'm willing to be proven wrong.
Do it! Test all the things, share all the results!!!
@@YUMBL i have a lot of things i want to test.
@@mrxmry3264 maybe setup screen recording and share the results? Obviously doesn't have to be a full video, just some clips.
yeah i was wondering too why cars were not allowed to turn right on the lights full time^^
Also if you have right turn only lanes then the adjacent direction can turn right while the other traffic is still going. I tend to do 4 cycles like that and leave 1 for pedestrians only. Traffic is not a thing any more.
Tl:dr: timed traffic lights and micromanaging which lanes go where can have some extremely beneficial results.
Woo Hoo like number 1.8K! An interesting experiment. Now to see what Biffa has to say about it. Keep up the great work!
After 3,756.5 hours of playing this game I’m glad someone is finally saying it. I ONLY use roundabout intersections at 1/2 asymmetrical roads or 1/1 roads in suburban neighborhoods. I believe in grids. Grids work. High density cities work avoiding using too many highways is the best bet for the vanilla gameplay start small build out organically and focus on walkability and bikes I avoid placing Stroads all together if possible. I was wondering if everyone is so afraid of Biffa 😂 that they have to play just like him.
You are absolutely correct, Yumbl. I had to switch out a lot of roundabouts for a 4-way lighted intersections because I've found roundabouts to be inefficient.
Just on the biggest roads, but yes.
@@YUMBL Correct. Only on the biggest roads. No matter what I tried I could not get my roundabouts to flow in heavy-traffic conditions. I finally gave up, removed them, then added a 4-way timed-light...and voila!
This is what I’ve always thought. Every single bad intersection I’ve ever had was very easily solvable by using timed traffic lights: no need for the removal of buildings and it always seems to work much better than roundabouts!
The most traffic-heavy areas of my city all have custom set ups of traffic lights that conform to the needs of the specific intersections (like longer green lights on the main road, for example). And my traffic flow rarely ever dips below 85%. The city is at ~340k pop.!
😂 YES!!! Thank you for showing all your work and handling the oft-used arguments. I get European city builders complaining that I use too many intersections and that I should use roundabouts instead of traffic lights ALL. THE. TIME.
I love this test too because you used what I would call the _least_ efficient traffic light setup (one direction at a time + nonconflicting right) and it _still_ blew up a moderately efficient roundabout.
Thank you 😁 and of you really want to make some heads explode, show them a CFI or even a quadrant intersection 😜
Thanks Lee! Love what you do. See the last 10 seconds for roundabout decimation 😉
@@YUMBL oh I was laughing my head off just like you! 😂
Besides the CFI and the quadrant, it would be fun to see the roundabout signalized. I think a signalized roundabout would perform MUCH better because the problem created with saturated traffic density like you have here is that only one entire direction can flow at a time, rendering multilane roundabouts pretty much useless, because three directions always have to stop anyway, and they don’t get a very long window of continuous flow. Therefore signalizing the roundabout would drastically improve flow, as one direction would actually get some momentum going...just like the timed traffic light.
This all reveals the _real_ reasons for roundabouts-it’s not all about continuous flow, because obviously with high enough traffic density there is no continuous flow. If you want continuous flow for high traffic density, as you pointed out, an interchange is the way to go.
Someone poi ted out in a comment that roundabouts are bad where flow is too little (overkill) or too much (it locks up) but is great everywhere in between. I would tend to agree, space allowing. But the “space allowing” part can’t be understated.
@@YUMBL amen! They don’t retrofit these into dense urban areas all that often...not even in Europe.
Awesome video! This generated a ton of discussing and reading the comments was enjoyable. It was odd to me that most traffic wanted to go straight; I don’t understand the game’s rng and why it would prefer intercity routes to be fully across the map
tbh I think this is not so different from real life. Roads are built along important routes, meaning traffic will want to go straight (stay "en route") most of the time when hitting an intersection or interchange. As infrastructure continues to develop and more destinations spring up, the existing road may be sufficient to act as a route between these new places, so you get additional right or left turning traffic from this. But if that left or right turning traffic becomes too much to handle, you can create a bypass road along this route, splitting these two important routes onto separate roads so they don't intersect anymore. But that just means traffic will want to go straight again.
This is all because of a basic property of geometry. Let's consider the location of an interchange and call it A. Then let's pick two destinations so that to get between them via A you need to turn left or right. These are B and C. Going from B to C via A can _never_ be the shortest possible route from B to C. It _may_ be the shortest route _currently available_, but it may also not be. On the other hand, if you're going straight across an intersection, this theoretical "idealness" of your route is not impacted. Other intersections, or even bends in the road, will likely do so, but the issue there is not with the fact that you've used the intersection.
TL;DR: turning has more potential to make a route longer than it needs to be than going straight, so it's likely that hypothetical turning traffic will be able to find a better route, removing them from the intersection entirely.
You can't have a lane doing two things. It needs to be two lanes straight, one lane off.
I've used a couple roundabouts to replace lights, but in almost every case I've had to remove them and upgrade to something better. If a 4/2 asymmetrical intersection with timed lights won't keep up, chances are the roundabout won't either. I've upgraded a lot of my major intersections to simplified CFIs, and although they take quite a bit of setup with lane arrows etc, they do move a lot more cars. Partly that's due to just having more lanes available, and partly due to being a 2-phase traffic light.
Where I live, we have a roundabout that is managed by traffic light, I think the reason for it is because there is a tram track that is going straight through the roundabout and to inusre safety they've added traffic light.
Makes sense!
I have similar experiences. I've followed suggestions such as lowering the roundabout speed "to let more cars in" but all that seems to do is reduce throughput. I've also made it bigger, added slip lane right turns, etc. but stuff like that just makes it take up more room and eventually approaching the size and complexity of a proper interchange. Meanwhile the timed intersections move a lot of traffic in a small amount of space.
Honorable mention goes to raised or lowered roundabout functioning as an arterial exit, but that's still medium duty in my opinion. I think roundabouts can offer utility in suburban settings, like a low density neighborhood transitioning to a strip mall area. Otherwise I think the big benefit of roundabouts is that they're probably the best option when Traffic Manager isn't available. The vanilla lights are absolute trash and, in my opinion, worse than completely uncontrolled intersections. Due to lack of lane control, many common heavy intersection configurations aren't viable in vanilla C:S.
Personally, I set the traffic light minimum time very low, usually one second but up to four, and use the flow control slider to control traffic. This way I don't need to be concerned about dead periods where nothing is moving when traffic is asymmetrical, which is probably usually the case. The ideal configuration is the one with the fewest light cycles since you lose throughput during light changes. As this video suggests, very long cycles typically moves the most traffic but the roads need to be configured in a way where the cars can queue. That is, it's not going to work well when there are intersections right next to major junctions like this. In those scenarios, the flow meter needs to be set more to the right for more frequent light changes.
There are more options to handle pedestrian traffic with a timed intersection. Even under "auto" settings they tend to get in the way of cars less than when crossing the roundabout. They can be given their own light cycle, which is fun to watch. It's like having your own Shibuya crossings. Pedestrian overpasses or tunnels are options in either case, though.
A very reasonable conclusion :)
Very interesting, any ideas that give us pause for thought and consideration are of value in this cim game.
Agreed!
Great video. This is something I suspected for a long time, too. Using timed lights vs roundabouts, in any configuration, really, shows that timed lights are always or almost always superior for high density traffic. I hope to see more in-depth and more scientific videos about intersections :) Maybe some mod to actually measure traffic flow?
Great experiment!
My two remarks only due to my experience in real life as a driver in several european cities
- Roundabouts work better when they have a number of lines equal to the max number of lines in the roads getting there, plus one. So in this experiment i would have tried also a 5-lines one way road for the circle. Maybe it's worth a try.
- Roundabouts work MUCH BETTER when they are at intersection of roads with different density. When you have (such in this experiment) two high-density roads traffic lights are better, while when one of the roads has a lower traffic flow the higher density one takes advandages of the lower. This does not happen with traffic lights.
Of course these remarks have to cope with the CS traffic AI engine, which may be (very) different from real life.
You've convinced me that roundabouts don't work as well as traffic lights for high density (in cities skylines), all though I'm still going to try to make it work with this interchange testing map.
Roundabouts are still my choice for lower density intersections, especially when I have more then 4 streets intersecting at once.
Lower density roads DESERVE a roundabout, space allowing. Thanks for watching :)
Love your analysis
Thanks a lot :)
I tend to agree that in this particular instance that a roundabout doesn’t hold up well. However I don’t think a roundabout would be built in this scenario with heavy traffic going in all directions. The roundabout works well when you have a singular dominant flow of traffic that you want to prioritise without holding it up with (even short) light phases
I ran into this problem a while back, so I made a really compact full clover for collectors (the biggest roads I tend to use outside of highways). If you set up traffic manager correctly it flows almost completely freely for most traffic conditions and takes up about the same space as the roundabouts I tend to make. I'd be curious to see what a magic roundabout would look like here, but that would be even bigger.
I'm a dedicated Biffa fan, so I LOVE roundabouts. But this was a fascinating video, and a very compelling demonstration. I think you might get even better results by altering the timing of the lights and playing with some of the advanced options ("more waiting than driving", etc.).
The light was suboptimal, yes :)
Agree 100%. I hardly ever use roundabouts anymore. I only use them as an aesthetic choice when I know the traffic isn't going to be too bad. I use tm:pe simulation accuracy at very high and the dynamic AI lane selection at 70 and the timed lights are far more efficient. Medium traffic on one pair starts to choke the traffic on other street pairs and heavy traffic just kills the whole thing, but a well set up traffic light keeps everything under control. Just have to tweak the light to find the right timings sometimes.
This was extremely interesting! I never understood the fixation with them and have never seen them effectively used in heavy density. Even in real world they are a pain to navigate as you run into the proverbial "who's on first?" routine.
one thing that always gets me about multi-lane roundabouts is that if you have to turn left on them, you have to cross 2(+) lanes to get in to your lane, which can be close to impossible sometimes. so that can easily cause massive backups, with the traffic lights you just wait for your turn and empty the entire lane all at once. so as nice as turbo roundabouts are, i'd never really go for one with more than 2 lanes, if you need more, use multi-lane traffic lights like yumbl did, or just make it a highway interchange
The outer lane should always be the merging lane and the default lane
yumbl: conclusively roundabouts are not the best option for high density roads in cities skylines
commenters: I CAN'T BELIEVE YOU HAVE DISPARAGED ROUNDABOUTS, THEY WORK WELL IN LOWER DENSITY CONFIGURATIONS, THIS TEST DOESN'T ADDRESS MY PARTICULAR USE CASE
would be dope if people actually watched the whole video before feeling the need to defend their beloved roundabouts
This is so fun 😂
Thank you for doing this.
@10:07 something isn't right there. The cars on the roundabout stop to give way to quite a few cars entering the round about and they shouldn't do. This has a knock on effect blocking other exits. Maybe it is the AI level?
Show me the solution!
@@YUMBL 2:40 turn up simulation accuracy in the TMPE settings :) Otherwise they just won't yield properly.
@@thebestspork This plus as seen in some of the footage with the timed traffic lights, some of the vehicles jump the lights and attempt to cross traffic before it clears. Simulation accuracy needs to be high or very high if we want to be as realistic as possible when comparing junctions.
SHOW me.
@@YUMBL So it appears it isn't the AI setting that does this, the Simulation accuracy seems to control how well the ai responds to the yields. With it set to very high, they will stop on yields as needed 95% of the time. That doesn't solve the traffic flow though, the timed light is still better even with the yields working
Love the chill music.
Yeah! Down with roundabouts! Stack interchanges everywhere!
Here, have a “mini-stack”!
In before you blow right up! This man's videos are exceptional, genuinely informative. Keep on keeping on my good man 🤗
Much appreciated :)
I'd like to see the comparison between a grade separated interchange and the lighted intersection to compare their throughput this way.
Excellent idea! I bet it gives lesser interchanges a run for their money
This please. Especially if there is some sort of automated way to generate intersection statistics, like average speed, or cars per second, average waiting time, or something. It also would be interesting to see a (super)turbo roundabout tested.
I would love some sort of flow meter. Believe me, i’ve asked around.
This is why in Europe most roundabouts are on single maximum two lane roads. The main benefit of reduced collisions is also negated when more lanes are added. 4/8 lane roads are not very common and would be grid separated anyways, there are reasons why the US has different systems in place that Europe. Stroads and lack of alternatives to the car (sometimes caused by planing deficits/ huge suburban sprawl) are way bigger problems and while the roundabout is a great invention and useful for smaller roads (when implemented correctly) it is not the tool to replace all traffic lights, which is also the reason why we still have them in Europe as well ;D
Traffic management to me, is the most fun AND most frustrating aspect of the game 😆
It absolutely makes the game :)
So satisfying watching the timed traffic lights and seeing all the lanes being used. I've always preferred them to roundabouts in the game since they take up no extra space.
That's pretty close to scientific proof, very well done.
You could slightly boost it by telling straight lanes to ignore the very right one, leaving it for right turn only. Then modify lights to right turn always green or "allow right turn in Red" in TMPE Options. Single-Node- Sliplane
However, I still love watching traffic at roundabouts, not stopping at lights. For eyecandy I'd still opt for the roundabouts.
High appreciation for your kind way of presenting, thanks
Thank you! I think both look great :)
Yup found this in a game called Motorways. Roundabouts are mostly good for big intersections but for small ones a traffic light is just what you need
_Biffa will remember that_
Yeah I've reached the same conclusion. I still think they have good uses though but they're by far not a catch all solution.
Edit: also thanks for the test map, I was curious how you did your testing, I'll definitely be getting this.
As with every type of road junction they are useful in the right situations. Once you reach a certain density of traffic they do create traffic backups, so a lot of very busy roundabouts here in the UK have had traffic lights installed on them to help keep the traffic flow even.
One of the main advantages of them IRL is the safety aspect, which is obviously not something that needs to be considered for the simulated traffic in C:S.
All correct :)
FINALLY!! Someone who doesnt throw friggin doughnuts at every traffic issue whether it makes sense or not (and in many it doesnt).
One main excuse is safety...but this is a game...plus, you cant have fast moving, high volume traffic 3-4 lanes wide "controlling itself" to yield, merge, shift lanes in circle, get out, etc properly or efficiently or there would be a pile up every 5 minutes. Seriously, people are stupid and dont pay attention; they crash regularly on the straight highway trying to change lanes and more often at on\off ramps, bringing traffic to a hault for miles...yet you think they could handle a roundabout like this? Lol, thats hilarious.
Yeah they work in cases, but so does many other things. To me its a theme thing, not a best function thing...but everybody for some reason doing CS videos started using them everywhere, maybe the lazy way out? I cringe even hearing the word as ive seen many ppl on here build them religiously, got to the point i stopped watching builds and especially traffic fixes because i already knew what was coming. Thank you for giving me hope again!! Lol...
Anyway love ur vids dude, you do nice work
Thank you :)
Interesting argument. With traffic flow, I tend to do a DDI or stacked roundabout. Though when I do make roundabouts, I normally don't do a 90-degree input. Usually brace the roundabout with the inputs at the 90-degrees, but then add lanes to those inputs at about 45-degrees from them. It's a little bigger, due to needing 9 extra roads to reach their destination, but it seems to work. Though I do have spots on a map where that didn't work.
Notification Squad, let's GO!
As a Texan who travels this big state it is hard to find round abouts so I am a little bias about signaled intersections. However, Texas has had it's many shares of unique hybrids that are part roundabout, part signaled, and part overpass. It's really interesting how TXDOT really builds their roads. Love the videos thank you for them and keep making them!
Wow!
That actually changed my mind about roundabout.
I used to think that roundabout saves everything.
Now, I will plan better!! THX YUMBL
Thanks for watching :)
Sorry, disagree with this video entirely, you can't make a custom intersection (Which worked very well), and compare it to a basic roundabout. The thing about roundabouts is, the busier they are, the larger they have to be. If the roundabout was bigger, had proper exits and entrances and slip roads, roundabout always wins. I had a nightmare city once, with 3 main intersections on the main road. I changed 2 of those to roundabouts (pretty big, proper slip lanes) and my traffic was cured almost instantly. Always love your vids, but I just don't happen to agree with this one.
Was this a basic roundabout? 4 lanes, fully managed? Can I count on you to create an experiment to show me, or is this a flippant comment?
@@YUMBL to be honest, I don’t see what is flippant about it. I happen to disagree also, since roundabouts are pretty much a solution on multiple occasions. It does need sliplanes, vehicle AI upped and good speeds on entering and on the roundabout itself. Setting a nicely managed timed light with separate lanes versus a regular roundabout is not an equal footing.
Also actual turbo roundabouts are a different beast entirely.
Its only a flippant comment if one is unwilling to back it up
@@YUMBL not to be pedantic but he wasn’t being disrespectful.
One thing I did notice on the intersection is that people are actually waiting a long time. Although the roundabout has one lane on two sides stretching out, it would be interesting to see what the actual throughput is on both. I’d reckon it is not all that different, given the fact that the actual backup doesn’t seem to keep expanding.
No one was being disrespectful. I dont really know what you mean.
In my current city I have replaced most of my roundabouts along the arterials with timed trafiic lights since the roundabouts always seemed to cause more backups. So I agree with your point. However, where I still have roundabouts I make sure that the roads connecting to the ring come in at an angle (not 90 degrees). That seems to greatly improve the flow and it would be interesting to see a new comparison where both the traffic lights and the roundabout are fully optimized.
*Europe has left the chat*
On mainland Europe, the most common kind of roundabout is a single lane roundabout, possibly with sliplanes, and often three-way rather than four-way in the industrial / commercial / office areas that are often found between large roads and cities. There they work nicely. For anything heavier, you will find interchanges, where there is space, or intersections.
As an englishman I quintessentially disagree
If custom demands, I understands.
In Argentina we don't turn left on avenues or highways. It's not a thing! You have to turn 3 rights and it's totally fine. Well, we do have designated left turns but they are very circumstantial.
So you're saying a roundabout doesn't work for a junction it wasn't designed for, big shocker.
By making this one junction the only connection between highways it's essentially a system interchange.
A roundabout is not a complete system interchange, it cannot cope with all that traffic. It can however be part of an interchange if you grade seperate the through movements and use a roundabout for left & right turns only.
This video is an unfair experiment because you are trying to make a roundabout do something it simply cannot do.
The function of a roundabout isn't for dealing with a large volume of traffic. The function of a roundabout is to increase safety over a normal junction with traffic lights.
The traffic light didnt seem to mind ;)
Might not be a big shocker for you or I, but seems to be news to quite a lot of people. The setup is quite artificial, as all experiments are, but it is entirely possible to set up worse conditions by accident, and this is a good demonstration of the limits of roundabouts. The whole point of the video is that it highlights what roundabouts cannot do.
The challenge is not insulting Biffa at the same time, which is I think why it's tone is so scientific.
Came here to the comment section to see the "Biffa goes REEEEEEE" in his British way, and I was not disappointed. Looking forward to his response XD
At this point it's really just logic - above a certain traffic density, you run into issues with traffic in the roundabout having to stop when a vehicle decides to enter the roundabout, which completely seizes everything up. I've had situations where roundabouts have completely gridlocked on me, and putting in either a well-timed light or a small interchange was the solution.
Correct! Exactly. Not everyone likes that answer though.
I just banned cars in the city, and residents get somewhere exclusively by public transport. There are almost no traffic jams, only on the end sometimes, but if you build the final ones correctly, there will be no traffic jams. Public transport top!
Popped in from Biffa, thanks this is quite informative.
The traffic light mafia got to Yumbl!
Let the great Yumbl/Biffa war begin! This is the entertainment I seek.
Bro I'm just shocked, I never even thought of using traffic lights since lots of people say that they are bad in the game. I've always wondered why there are mods for traffic lights since they are bad, you really changed my mind.
I’ve never heard anyone say theyre bad. People just tend to rely on roundabouts and never learn how to set up lights.
@@YUMBL I remember that biffa always says in his fixing cities series that they are bad and he always removes them. He only uses them when is the last option. Also in his vanilla 2021 city he never uses them aside from the main road he build in the middle because he doesn't have traffic manager. If he had it he would just give priority to the main road and make everyone else yield.
Oh, the vanilla traffic lights are terrible. That much is true
Hello. European traffic engineer here. Why do you have roundabout exit setting so "unequal"? You are leaving into 3 lane road but only have 2 lines exiting the roundabout. Also for such a high traffic scenario, you would choose "turbo roundabout" (don't know the exact translation) where entering lines form new lines on the roundabout (no right of way issues) and exiting lines end at the point of exit (again no right of way issue).
This seems to me to be a highly optimized light-controlled intersection against a very basic variant of a roundabout, in which the roundabout will certainly lose (See Matthew Wong's comment for further analysis).
Please feel free to show me if that type of setup works. It seems impossible to have three lanes exiting safely as traffic would have to cross over each other.
Also, the light was awful. It would be much more efficient if it had lefts going at the same time to shorten the cycles. Strange to me that a traffic engineer didn’t notice that.
After trying out RABs throughout my city, and YES I configured them properly with the right tool, I figured out regular intersections configured properly were much much better than RABs!
Your findings have been reproduced by scientists. In France roundabouts are everywhere, in Germany planners are fighting for the crossing with lights: so studies were made that do prove that under heavy load lights are better. Roundabouts can more easily adapt to dynamically varying loads and are better at low loads.
Personally I totally love roundabouts. In southern France they are at all entrances to villages and serve as an unobtrusive speed damper. My frustration level is much lower when I'm in a continuous slow flow rather than intermittent stops. In recent years my - old - home region has been plastered with roundabouts and I barely recognize the roads anymore but driving is so much more fun / less annoying that before.
Agreed on all points! Roundabouts are excellent in many spots, and take up a lot of space, and slow traffic (many times in a good way), and break down with enough traffic.
I have built many, many, many cities since C:S was released. I've used traffic lights and I've used roundabouts. There was a series of cities where I overused roundabouts (it just so happens to coincide when I started to watch Biffa's channel). Then I found Lee Hawkins and I've basically abandoned, mostly, the use of roundabouts and have gone with the many connections theory that helps to spread out traffic. It's amazing how well that approach works. You'd think an intersection, even a four-way, every 12 units would cause backups. But it actually doesn't. What causes backups is if I make that a priority road using yield signs. It's unreal (and yes, I use TM:PE)
It seems to me that roundabouts could come in handy in specific conditions where you want to slow down traffic a bit. Maybe the transition from one neighborhood to another. I know in Arizona, in the Sedona area, they have multiple roundabouts (though they don't actually call them roundabouts) on one of the major roads. it helps to slow down the traffic.
I've read through some of the comments and I would love to see a counter video from Biffa. I love both of your channels. You both have unique approaches to the game and I'd like to think I've adapted my own playing style to take into account what you guys do. As a result, I'm a better player and my cities are better than ever. Throw in ideas from Lee Hawkins and I've got some awesome cities (not to mention CPP, as well).
This was very informative. Nice job Yumbl. I think you need to be invited to the next season of 5 Builders, 1 City.
Thank you very much! I overused roundabouts for a long time too. Theyre a quick and easy solution to a point.
@@YUMBL It doesn't help much that one of the traffic tips offered during a game load (if you are not using the Loading Screen Mod) is to create a roundabout when you have heavy traffic. That could very well be where players get the idea to "overuse" roundabouts.
Love this example of how roundabouts aren't meant to be used on very high capacity/throughput roads. Roundabouts funcion most optimally in areas where you want traffic calming and an "equal priority" with a large and smaller road.
Precisely :)
Well I've lived in Dubai for a good while of my life,.. and their traffic design has always been:
-local roads use roundabouts
-collector roads uses intersections
-'highways' are always over head passes.
And I have highways in quotation marks because most of their roads are 100+ km/h and are considered a highway.. that's why u see some really complicated highway systems in pictures of it xD
But supporting your hypothesis, and also the way I've been integrating it within my cities, intersections provide better flow than roundabouts for high density traffic.
Must admit, I had no idea how to set up,a timed traffic light on an individual basis so just the shortcut has helped massively!
Oh, its so good. You may need to play with timing, but its a life saver.
Hi
I watched some of your roundabout videos they are really interesting
I live some where that is really crowded place and roundabouts are every where
So much traffic no road management
there is no collector roads
and residential and commercial is a nightmare how they managed to spared it
Just watching your videos gives me so much ideas you know
Simulation is a really great way to apply things before making a thing
Thank you very much :)
Nice video, but I'm afraid that without a mod that counts how many vehicles have passed node with a given amount of time results will be widely disputed.
With that flow setup I'd say that the difference is the same that we have in the current. With roundabouts we have direct current - traffic will be more less stable. With the traffic interchange you will have alternating current situation. The tail will be raising and falling.
The roundabout tails were trending longer and longer with time. As per my hypothesis though, are you suggesting that roundabouts ARE the best option on high density roads in cities skylines?
@@YUMBL No, you cannot say that without auditing the numbers. I'm just pointing out both could have different repercusion to network system. For example intersection could be better when near buildings that suddenly generate huge influx of vehicles. Roundabouds could be better in places where there are neither of these. But this should be tested in different environment.
If you have a good way to count the cars i’m all ears.
@@YUMBL There is some old video where somebody managed to count this v=yITr127KZtQ sadly one mod link is not working anymore :/
What could be done is let the intersections run, select the last car in line, and see how long it takes them to cross the intersection. I see the success of a junction as how long (short) it keeps people waiting.
Gotta appreciate the effort to actually test this ! But I would like to add that idk for the us, but in France 50 m diameter for a roundabout is quite small. It’s what most light traffic roundabouts would be like. Huge roundabout r usually more than 100 m in diameter (sometimes up to 300 m). And for traffic lights 15 - 25 cities Skylines time units is quite long (and would be in comparison a long time for a traffic light in France).
Still appreciate that you actually took the effort to test this.
It was a 56 meter RADIUS. Not diameter
@@YUMBL Oops my bad. Misheard it
Roundabouts are a good intersection for medium traffic or asymmetric traffic.
Too little traffic and they dont really offer anything over stop signs, and they break down with too much traffic because of human nature mostly.
However they do work good in merging a medium density or high speed road with smaller roads, as they give joining traffic a bigger opportunity to get in, and make left turns almost trivial.
Roundabouts are the best overpass free uncontrolled intersections, however at higher or highway density, traffic lights and bridges show their might.
Hear hear!
Very enlightening. I'm going to give this a try. (But the hidden gem is the "N" you placed at North to help negotiate the direction of the map!)
Always leaving hidden gems ;)
I wonder what both would be like. Timed lights on a roundabout. I can't test it myself but I really would like to see the results. Very interesting video, man. Thank you.
You would end up with the same result as the stoplight, but it would take longer to clear, making it a waste of space and time.
I can already feel Biffa's anger. Help me set up the emergency tea hose! Before you ask, Yorkshire. A spiffing old brit told me it was the best.
One of the biggest misconceptions with roundabouts is that they're better for traffic at _any_ density. In fact, roundabouts are best for the vast majority of situations, but only in the gap between "almost no traffic" and "way too much traffic". If there is only one vehicle interacting with an intersection at a time, 4-way yield is most efficient, since vehicles can just keep driving through without stopping or even slowing down. If there is a massive amount of traffic, the cars trying to enter the roundabout take up more space than the ones already moving, and can often slow down the cars already in the roundabout. That, or they have to wait for a large enough gap to enter.
In a well-managed timed traffic light, intersection time is only "wasted" for a short period of time while one phase gets a yellow light, until the next phase is at full speed. The longer a particular phase is, the more efficient the intersection is, as long as there is 100% traffic flow through the intersection during any given phase.
I'm kind of surprised you didn't test intersections using the other common phase patterns. The most common pattern I've seen involves opposing lefts getting the green, along with the complementary right turns, followed by opposing straights with complimentary rights, then alternating with the perpendicular directions of traffic. This can optionally be added on to with an effective yield for left turns during the associated straights phase (though this is often not allowed if it would be overly unsafe for that intersection, as is the case with double left turn lanes). This particular pattern is better when it can allow more simultaneous paths of traffic through the intersection. In your example, you had one left, two straight, one right lane getting the green, along with a single complimentary right turn lane starting from the entry point cw from the side getting the green. That is a total of 5 lanes of simultaneous traffic plus 2 yields. Instead, you could be getting 6 lanes during the straights phase (two straight in each direction, plus safe right turns), plus 4 yields (both associated lefts, and the remaining rights), and 4 lanes during the lefts phase (opposing lefts and complimentary rights), with 2 yields (the remaining rights).
If all lanes are getting equal use and the phases are equal lengths, it would be the same in either case, but there are many cases that benefit one over the other.
Either way, great video!
Thank you! The light is nearly default and easily set up. I wanted to offer a baseline of throughput for the light that anyone can replicate with ease. An optimized light (cycles, turn lanes, etc) DECIMATES a roundabout at high traffic volume.
A problem with both Traffic Manager and the vanilla lights is you can't tell them "green but yield on lefts". You might be able to fudge it with the advanced Traffic Manager conditionals I've never seen anyone use, but the core logic isn't there. As a result, round robin signaling tends to dominate.