Cities: Skylines - Good Traffic Guide

Updated: June 8, 2018

This splendid city building simulation is no stranger to Dedoimedo. I've talked about the game at length, covering both the original release and the combined After Dark and Snowfall expansions, and recently also covered the relatively new Mass Transit DLC. But that's not all. We have also talked about traffic management. A lot.

Like most urban simulators, the game places heavy focus on the road infrastructure - let's face it, a city cannot function without transportation, and everything else is a derivative of the tarmac grid, even if you do not really use grids in your games, ha ha. I've shed some personal advice on how to handle smooth flowing traffic against organic city growth, and the use of underground tunnels to achieve extra throughput and better aesthetics in your cities. Now, with Mass Transit offering a whole new range of additional transport technologies, I wanted to compile a complete guide on making your traffic perfect. Let us.

Teaser

Tip 1: The perfect road shape

Most of your game traffic will happen on roads - everything else is there for fun and cosmetic purposes. The big haul will happen on streets and highways, with cars, buses and trucks doing the bulk of the work. To wit, you need to make sure that your infrastructure can handle the volume of traffic, as well as cope with the pathfinding algorithms in the game.

Let's start with the latter concept. The game uses shortest-path routes rather than quickest path. Modern, real-time navigations systems are trying to become better and better at prediction congestions, so that people can divert to other roads and get to their destination faster, even if it means a longer route. Cities: Skylines does a simpler set of calculations, and this means you will have to be one doing all the thinking. The one redeeming factor is that cars will generally prefer highways to streets, regardless of the distance or time, so you have some leeway there.

The other element touches on the physical presence of your citizens within the city limits. You don't actually have to connect all the districts to achieve population and demand boosts, or affect traffic, for that matter. So even if you do feel like having a neighborhood of workers close to a particular (industrial) zone, this does not really mean that people in your city will live based on work proximity. Services and business will behave based on supply & demand, so those should be well-interconnected, but it's not a linear equation. In other words, as long as you can shift produce from industrial zones fast enough - especially outside your city regions - and make sure that your commercial zones are connected to highways, you should be fine. You really don't need to micro-manage your citizens, and you cannot really force people to migrate where you need them. This happens organically, so just focus on building congestion-free roads.

The best way to achieve good traffic throughput is by using roundabouts. Everyone knows this. But then, what if your roundabouts become congested? You build more. There's logic in this madness, and I believe I've discovered the ultimate complex roundabout layout. It's a double two-entry three-exit polygon. Let's elaborate.

You spin me round ... again

With right-side (left-hand drive, LHD) traffic, roundabouts are counterclockwise. This means you exit to the right, but you also enter to the right. So you want your traffic to travel as little as possible from the moment it comes into the roundabout before it joins the streets, and the same way, clear the roundabout as soon as possible on exit from districts toward other parts of the city, or the bigger highway network.

But what if you have streets on "several" sides of the roundabout?

In that case, you want to repeat the entry-exit placement on each side. For the sake of simplicity, let's assume that there are only two sides. If they are directly opposite one another, you have a symmetric shape, and the two zones open a 180-degree angle between them. If this angle is less than that, you have just started building your polygon, and the the angle between two adjacent sides (plus the length of your zones) will determine its shape.

Roundabout concept

Blue lines are streets; red lines are the roundabout itself and the highway entry/exit connections - 1 and 3 are exits, 2 and 4 are entries.

The ultimate shape is probably the hexagon - more than that, you start building a huge loop, if not quite circle, of roundabouts connected to one another via adjacent neighborhoods, on both left and right; less than that, and the zones will be quite small and cramped, with little to no growth potential, and you may also hit the issue of asymmetry.

Hexagon

What if you want traffic to go across?

Aha. So if you have six roundabouts, then you also have six zones. But since your traffic is going in a CCW circle, this means that a car that wants to go from say R1 to R3 needs to cross through Z2 streets as well as R2, forcing traffic through a roundabout without really exiting. This creates traffic pressure, and it becomes even worse for R1 to R4, or any half-circle movement.The solution to this is to branch off every exit (for nearside side of the polygon) three ways:

Hexagon, roundabout connections

And since we have two sides to each roundabout, we build the same thing on the "opposite" side, hence the two entries and three exits. Now, you can make this even more complex. You can interconnect the highway sleeves that go around residential and commercial zones so that your traffic between non-adjacent roundabouts can skip having to enter onto the roundabout just to exit on the next highway ramp and continue the journey to the next roundabout.

Hexagon template

Creating the ultimate city traffic network.

In the end, you will have two ring roads, both supporting highway traffic - one outer, leading traffic away from the zones and toward other districts or cities, and one inner, supporting fast-shuffle of cars and buses between zones, allowing your vehicles not to have to ever go through residential zones they do not need, or drive through a roundabout without connecting to a residential zone.

Hexagon view 1

Hexagon view 2

You wish this was the situation in real life! Imagine never having to actually go into a neighborhood where you don't live or have business. You have only one stop on and off fast highways. And indeed, the proof is in the pudding. In my master prototype city, the very first neighborhood I built is a large hexagon with two rings of highways. The city has since grown to about 105K people, and there's very little congestion. The only pressure is on one of the roundabouts that connects to other districts directly, and this breaks the shape symmetry. Even so, it's quite manageable, and you can always create additional paths onto the internal ring if you need to. Splendid.

Additional roundabout tips

Here are some extra special McDedo nuggets for you:

You want to make your roundabouts big. Even the large one - which is offered by default in the game, with its four road connections at a rather impractical 90-degree between each two - is quite small. You want your roundabouts to be big enough so that your cars have enough time to move between lanes - inside for later turns, outside for nearer right exits. If the road connections are bunched too close apart, you may get a speed slowdown, which could lead to traffic building up.

Mass Transit introduces brand-new four-lane highways. They sound amazing, BUT. If you use them for roundabouts, you will discover that you end up with traffic lights! The three-lane roundabouts have no such problem, and so they are essentially much faster even though they have technically 33% less throughput than the larger siblings.

If you do go large, and you do use my system (hexagon), then city traffic will always go RIGHT. This means that cars will need to go around almost full circle if they want to reverse their driving direction. This is not a problem, but they will be driving past entries and exits of the opposite zone, and we don't want that. So you do want to introduce smaller back loops, which take cars from the rightmost street (however many you may have connected to each zone, usually 2-4) to just before the leftmost one. Or if you will, last and first counting counterclockwise. This way, street traffic remains restricted to its own zone, and it never goes around causing pressure on the ingress and egress lane for the nearby zone.

Large roundabout

Big roundabout, zoomed

Good traffic

Busy connection

Only a little bit of congestion where the hexagon symmetry is broken by an outside connection.

Trains, planes and automobiles

He he. But let's talk about trains. They are critical to your game success, even if you don't think about that right away. They are also rather buggy, BY DESIGN, making it an ever greater challenge. First, there is a limited number of outside connections. SimCity 4 allows you to plow roads anywhere you want, but Cities Skylines only has a small number of roads and rail tracks connecting to the distant cities. With the road traffic, it's not bad, but the trains can easily become congested.

Normally, and up to Mass Transit, train was mostly used to quickly ferry industrial produce from your industrial areas. I mentioned this in my first traffic guide, and we will talk about this some more still here. You now also have people stations and combined train-metro-monorail-bus options, which complicate things. You will be tempted to start running commercial lines too.

Rail hub

You will soon discover that the rail tracks get clogged up easily, and that if you try to solve this by placing additional tracks, as you would with roads, you will not get anywhere. In fact, you will even further complicate the situation, as the pathfinding algorithms go crazy. Once your train traffic drops, your industrial demand will plummet, and your cities will not grow as fast you expect. More about industry in a few minutes.

Time Train Timetable Tips

Repeat this 100 times, fast. Anyway, let's see what you can do to make your trains run well. First, try to maximize outside connections and use them in a balanced way. Take the number of lines and divide by the number of connections. Simple. Second, try to separate cargo from people.

Another important thing is not to create intersections - in real life, you see this a lot, and it's a thing of beauty, multiple tracks merging or branching, with intelligent signals and whatnot to manage it all. But then, in computer games, this is a beast. I never fully mastered the multi-track signaling in OpenTTD, and it remains equally tricky here. Actually more so, because you can do that in OpenTTD, but not so much in Cities: Skylines.

Train intersections

Very dangerous - your trains don't like this.

So don't. Avoid intersections. If you have an option to make simple lines, do it. Branch off only when absolutely necessary. Try to make circular intracity lines, if you must. If you don't want to loop, point to point will work, but then, there's no reason to do that as trains mostly serve for ferrying goods, and if you have metros or monorail, you don't need trains to move people around. And of course, there's no pointing connecting cargo terminals with people stations.

Intersections also must be longer than the train length - this is also true for OpenTTD - otherwise, a train will enter a signal section partially and stop while blocking the path behind it, and other trains won't be able to clear the little intersection, and you will end up in deadlocks. Industry demand goes down, and the cycle of despair begins anew.

Rail management

Your trains will thank you for it.

Simple tracks, lines or loops, with few stations, if any. I say, don't bother with non-freight lines, and for cargo, just connect to the outside world. You should avoid intersections and branching where not needed, and use those trains to haul goods from the industries. The more the merrier, and your demand will grow nicely. I've seen this escalate quite a few times, and it takes just a little bit of pruning to get your train traffic going smoothly.

Industry traffic

This ties nicely into the train topic, which is why we're going to discuss it now. Cities: Skylines is a clever game, but it does have a few dumb simplifiers. One is, there's no relation between physical proximity or connection of your residential areas to industrial areas in order to create workforce. Another one is, you may think that education affects industrial demand. I thought so too until hundreds of hours of extra playing taught me otherwise.

Yes, keeping your citizens smart is good - better jobs, better pay, more taxes, less crime, less pollution, etc. Everyone benefits from education. But then, your citizens will try to educate themselves like mad, and unless you tightly control the budget policies, you will probably end up with 60-70% of your people holding a higher degree. This will happen even if you don't place schools in some of your neighborhoods. Or even the entire city. Your folks will travel to other cities to learn. It's that mental. But it also means you don't need to be paranoid about your education in every district. This goes hand in hand with the overall workforce presence effect. As well as the rather strange parks boost effect, which you can use to easily manipulate the desirability of your zones and get buildings to level up, industry included.

So, education and workforce will almost always be satisfied as long as you provide facilities and housing SOMEWHERE within your city limits. And if you see your industry demand suddenly dropping and businesses going out of business, you may accidentally conclude that this is because you don't have enough people, or they may be over-educated. Nope.

Industry demand will almost exclusively be governed by how quickly you can send goods out. That's all. Add another two or three train lines - keep them clean and fast, remember - and you will see demand spike up, and more people moving into your city. Still, there are some extra things you can do. For best effect, you may also want to use a cargo hub or two near the coastline. If you do, short connections to highways will significantly help. The nearby presence of a train station will even further boost your ability to clear the warehouses, driving demand, and making your city grow.

Industry, roundabout

Train stations

Build them stations, don't be shy.

In the end, as a rule of thumb, you should roughly have one train station per 100 square-lengths of three-lane road - this translates into about 15 cm of screen equity on a 24-inch monitor with 1920x1090px resolution. You should also have very large roundabouts to allow enough time for your trucks to merge and speed up. If you do use harbors, remember to keep the road connections as short as possible. In fact, the best you can do is an off-ramp and on-ramp connecting directly to the prop.

Industry, trains and harbors

Bikes and pedestrians

I still haven't tried the new Green Cities DLC, but the game has always had an eco-friendly angle. It plays in your favor to use the green options, like city policies that encourage healthy lifestyles and alternative modes of transport. But the best you can do to lower the street traffic is to use bike lanes.

Normally, bikes will use footwalks unless you explicitly forbid it. You can also construct roads with dedicated bike lanes, in which case your citizens will use their own paths to move quickly from place to place. This is a very useful option. You can go faster and longer distance than pedestrians, although Skylines people also LOVE to walk. Moreover, bikes lanes can connect districts the way roads cannot - you can connect an outer road to outer road with short stretches of cycling paths, whereas car traffic often must traverse streets and sections of highways before they can reach other zones.

Cycling paths

Foot and bike paths

Then, make your people walk. Create underground or elevated paths, and make sure all your major roads that house commercial and residential zones can connect to one another. This is quite efficient, cheap and saves a lot of road traffic. If you have long six-way city roads stretching between roundabouts, people may need to drive or take a bus to get to houses and business in parallel streets. But if you cut across these roads with foot paths, you allow your citizens to walk a very short distance, leaving the streets cleaner, quieter, and faster for easier delivery and dispatch of goods and services, increasing value and boosting positive feelings among your people. Plus your roundabouts are reserved for traffic that is really essential, mostly zone to zone travel.

I often construct very long stretches of foot paths, and they are always busy, but the beauty is, they never get jammed. There's no such thing. You really can work around a lot of traffic issues by making your people walk. This is not entirely world-realistic, but then, it allows you to keep growing without bringing your road network to a standstill due to somewhat inefficient pathfinding algorithms.

Foot paths

Buses

This will be your third most important mode of transport, after cars, human-powered tools, be they feet or pedals, and rail for industries. Having a nice, decent number of healthy, uncomplicated, circular bus lines guarantees you will keep the people of your city happy, and somewhat minimize traffic jams on the roads. Buses can be used on any which street, including dedicated bus-lane roads. I would advise against this, because cars will not be able to use them, reducing your overall throughput, whereas buses can use any which lane on your normal roads. Make sure you have several bus depots around the town, as it simplifies network distribution.

Metro and monorail

Essentially, these two are the same, except one rounds underground and other above it. The concept is similar to trains, except you can only transport people and there are no intercity connections. Much like trains, you need to keep things simple and tidy, either with simple point-to-point connections and two-stop lines, or with circular lines connection your neighborhoods. Both are good at transferring people between distant zones, and if you obey the rule of single-tracked traffic, you will enjoy a boost to your demand. As a visual style perk, you can connect these two modes of transport to industrial zones, but you will not necessarily benefit from massive flux of people to work and back, mostly because there's no real need for that, and also because the system is governed by supply and demand, and there aren't that many people in the industrial zones.

Monorail

Other modes of traffic

Several DLC introduced various new transportation systems, like trams, bigger airports, blimps, and cable cars, all of which mostly serve an aesthetic function. They sure make the city prettier, livelier, and help shift people around in a more varied fashion. Let's briefly overview the pros and cons of each of these, and what you can do to make your city work more efficiently.

Airports do help bring in tourists, and they are quite useful. For best effect, you should build the international airport, and connect its co-joined metro station to one of your metro lines. I would also suggest placing a large bus central there, so you can have bus lines originate and terminate at the airport. This will help move people in and out of the city more effectively. Other than that, there's no real limit to the airport traffic per se.

Blimps are an interesting phenomenon. They are somewhat slow, and you cannot intersect lines. Since there's no different flight altitude available, you must make sure not to dissect your city. Long diagonal blimp lines will effectively break your city into non-connectible parts. It is best to keep them short and sweet, and to work with a star pattern, using a central set of depots, and then branching off from the hub spoke like. Another difficulty is that each blimp station can only take two lines at the most, and in any given closed circuit path you define, at least one station must also be connected to the depot. Take this into account when you build and place your blimp network.

Blimps

Notice the propaganda on the blimp - and the adjacent taxi stand.

Cable cars are a curiosity - and they work well if you have varying altitude and steep-sloped hills in your city, which you do not wish to terraform. Rather than place meandering serpentine roads, you can do the same trick with cable cars as you would with pedestrian and cycling paths; you can significantly shorten the journey and easily connect road-distant zones. They work well, and they are best done with two simple end stops.

Trams are yet another rail transport system. The added value is that they can offload some of the traffic, but they also add complexity to your network. If you place the tracks only sections, you waste valuable space, and you will be forced to build roads above or below, or go with a slow and inefficient set of signals and crossings. Instead, you should consider integrated tram-and-road layout. In general though, there's no real benefit to trams compared to metros, so it's mostly an aesthetic benefit.

Trams

Again, taxis are there to add color and variety. You can use them any which you want, but do remember that taxi stations do take premium estate with immediate near-road placement, and also introduce a bit of chaos to your zones, making people slightly less happy. In general, they are useful but not critical.

Overall ...

This little guide may sound somewhat complicated, but it isn't. Yes, you need a bit of time to figure out the pattern in what's happening, but once you see it, it's quite all right. A polygon system of roundabouts, lots of bike and foot paths, and trains for your factories will guarantee a steady flow of traffic and constant demand for your blue, green and orange zones. Airports can help with intercity traffic, metro and mono with intracity. The rest offers additional creativity without significantly shifting the balance. But then, it is somewhat similar to what happens in real, modern cities.

Traffic overview

In general, organic growth will play havoc with your planning. You will probably be quite patient and organized in the first few hours, but then, you will relax, your city will expand, and with this, a whole new set of linear problems with set in. You cannot really predict how the traffic will go, but you can be ready.

Connections

Connections, connections, connections!

Nice 1

Nice 2

Nice 3

Conclusion

Cities: Skylines is an awesome game. It's great fun trying to manage the chaos of the traffic network, and see if your ideas can match the madness on the ground. There will never be a perfect city, and the road system will inevitably get messier as you add new areas and build extra housing. Just remember to view traffic in circular patterns if you can, with strong bias to having right turns and then directing it all counterclock wise. In a way, the entire city becomes one giant onion of roundabouts, even if it does not look that way.

I am pleased with my experimentation, and I hope you will also find the results valuable. Polygons work like a blast, even if you build smaller scale and break symmetry here and there. Rail is monumental to industries and eventual growth of your city. It's really hard not to overemphasize this point. It's not education or desirability, it's the volume of export and imports. Rail it up, nice and simple like. Lastly, let your people walk, so your city can sustain additional numbers without buckling. Everything else is icing on this delicious digital cake. I hope you enjoyed this exercise. If you have any questions or suggestions, now is the time to hand them over to me. May your city building be fun.

Cheers.

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