Traffic guide by Perafilozof

This guide explain the traffic problems in Cities: Skylines in small, medium and large cities, and the reasons why traffic jams happen. It gives tips on which type of vehicles create most traffic problems. and how to take lane control and force traffic to use all lanes on the roads and highways. Game has hard limits on the number of vehicles that can be active at the same time which is about 16,000. The Traffic manager mod allows for despawning(teleportation) of vehicles to be turned off showing the real state of the traffic in and around the city.

Guide content and subjects

Traffic... This is the most searched topic about Cities: Skylines. And even after so many years of playing the game, it is still giving headaches to the mayors of virtual cities. I am going to write this out in several parts, as this is a comprehensive subject, but there will be videos attached so you can chose your preferred medium.

The core problem of traffic is made up of several elements:
1. Vehicle numbers and types
2. AI traffic logic, lane usage, path choice
3. RCI zone design
4. Highways - city's regional connection (entrance)
5. Roads network design

Each part of the guide will give you an overview of the problem, some notes about why it is so, and tips & tricks as to how to solve or go around those problems.

Part #1 Vehicles and hidden mechanics

First part is going to be about vehicles, what kinds there are, where they spawn at(start at), how they travel and how they teleport (despawn). Understanding all types of vehicles and the rules behind them will help you build better cities, and manage traffic more easily.

Text or video, pick your media of choice:

The short story:

In order to prevent a disaster, that is triggered by traffic jams and the city's service vehicles inability to reach problematic places in the city, we have to understand these vehicles, where they came from and how did they create that traffic jam. First question that we need to ask is: what types of vehicles where in that traffic jam? Well, the common traffic jam is made up by every type of vehicles: regional vehicles, delivery trucks/vans, cars and city services.


First up I will write about, Regional vehicles. These originate, as their name implies, in the region, outside the map, and they have two types. First type are the ones that are just in transit trough your city and the Second type are trucks and delivery vans who drive the loads of products for industry or finished goods for commercial buildings in your city. Both of these types do not have a home building in your city. They leave your city, and the region, after completing their deliver or if they are of the first type, they just transit through your city. Depending on their objective, you need to provide adequate road and highway network, so that they can finish their objectives quickly, and not create traffic jams in your city.

I advise connecting all your highways to each other, from the spot where they enter your regional, unlocked, map. You should use a highway ramp, dig it down into the ground and give transiting vehicles a single lane, and ramp, to take from one end of the map, directly to the other. You will need to do so for each entrance and connect it to each exit.

Second, I will explain delivery trucks/vans originate from industrial buildings inside your city. They spawn at industry buildings and, depending on their type and cargo, have the objective to deliver products or goods to the next building in the chain. By having separate zones in your city that send out and receive these vehicles, you increase the amount of time and space these vehicles need to finish their routes(jobs, objectives). If you produce more goods/products, than you spend in your city, you create extra traffic with exporters which need to find a way out of the city and into the region. Providing good, direct and fast connectivity to highways or cargo hubs becomes a must.


Third, cars are Cims personal transportation vehicles. You can't eliminate their arrival from the region in their cars, when they are at first moving into your city, but you can reduce their need for cars once they settle inside the city. This can be achieved by zoning workplaces close to residences, by adding pedestrian paths, and numerous public transportation options.


Fourth, city services add up to a large number of vehicles. Garbage disposal, Firefighters, Healthcare, Deathcare and Police to name just the main ones. Huge cities require very high numbers of these vehicles to function. And each type has it's objectives that can be made obsolete if they spend too much time in a traffic jam. A Garbage truck that doesn't pick up garbage on time, and leads to a Cim getting sick, makes for dead weight on a road and forces additional vehicles to be sent to those roads in form of a ambulance or even further down the chain, hearse if the ambulance doesn't get there in time. These domino effects can easily lead to abandoned buildings which leads to gaps in the electricity network which leads into ruin.

The despawning, teleportation mechanic and the in-game vehicle number limitations provide a helpful respite form unending cycles of production, consumption and 24/7 work hours that create endless traffic which knows no ebb and flow, and because of which, it becomes impossible to deal with traffic at small scale, if it isn't designed into the city from the start. Large and huge cities benefit most from these hidden mechanic and limits, as they are working without actually having to obey the same laws that govern small cities, like delivery times, actual physical quantities and having to drive or take a ride to work.

The long story:

With the traffic overlay, which has a traffic flow bar, players can see what is the overall(average) percentage number of the traffic flow in their city. A higher number, for example 75,80,90% is considered a great traffic flow in a city. Besides this, the overlay itself provides the "picture is worth more then a thousand words" effect with the color system of red for high traffic, all the way down to green, low traffic, that provides a quick way of spotting problematic roads.


This is a good visual representation, but it also lulls the player into a false sense of having a good traffic flow with the percentage bar, because of it's average approach. While 99% of your streets and roads might be green, and have close to no traffic, a single part of your city might be experiencing a 99% congestion, and a huge traffic jam. This will still give you a high traffic flow % even if your are moments away from a disaster.

Why a disaster? Well because things in Cities: Skylines tend to fall down like a house of cards, or a domino train. It goes like this: A section of your city is having a huge traffic jam. Garbage pills up as city service vehicles are unable to get through the jammed roads to the building and remove the garbage. A single Cim gets sick. An ambulance is sent out form a near by clinic, but it too is stuck in the same traffic jam, only adding to it. That Cim is so sick, and with no aid, he/she dies.

Now the cemetery / crematorium dispatches a hearse to pick up that dead Cim's body. But it never gets there. The body stinks up the whole building and it is abandoned after a short while. The longer the traffic jam lasts the more buildings become abandoned. And as this local event spreads, and more buildings are abandoned, they stop carrying over electricity. This is the final stage of this disaster as a break in the electricity supply stops every building from functioning and the city becomes a ruin as building after building is abandoned.

Also, Death waves... need I write more?

And so, is that one garbage truck to blame? No, it's not. It's all the other vehicles that made up that traffic jam preventing the garbage truck form doing it's job.

A note here: A city's production, work, buying(spending) cycle in Cities Skylines is not only endless, but it also knows no weekends, holidays, or even night shifts. It does have a day and night cycle but it doesn't slow the city's RCI system long enough to take the heat of the roads for the night. Industrial buildings create goods and products 24/7 and require Cims to work 24/7 and shop 24/7. This means that there is little to no ebb and flow in a city, but a constant unyielding pressure of hyperproduction an expenditure. I am not sure were the developers doing this on purpose to make a sociological/economical/political statement or it was just easier to make the game run like this. In any case the endless cycle is part of the problem as roads cannot clear as fast as more vehicles can spawn.


In order to prevent a disaster, like the one I described above, from happening we have to understand these vehicles and where they came from and how did they create that traffic jam. First question is what types of vehicles where in that traffic jam? The common traffic jam is made up by every type of vehicles: regional vehicles, delivery trucks/vans, cars and city services. And those can be broken down further.

Vehicle types

1. Regional vehicles, these originate, as their name implies, in the region, outside the map, and they have two types. First type are the ones that are just in transit trough your city, they move from one edge of the map to the other through the highways and your city, if your city has a connection to two highways that where not connected to each other at the start of the map. These vehicles are not counted in the Outside connections info view panel(import, export).

I advise connecting all your highways to each other, from the spot where they enter your regional, unlocked, map. You should use a highway ramp, dig it down into the ground and give transiting vehicles a single lane, and ramp, to take from one end of the map, directly to the other. You will need to do so for each entrance and connect it to each exit.


Second type are trucks and delivery vans which drive the loads of products for industry or finished goods for commercial buildings in your city. These vehicles are counted in the Outside connections info view panel(import). Both of these types don't have a home building in your city. They are spawned at: the edge of the map, on a highway, or at a cargo station (train, harbor, airport). They leave the city and the region after completing their deliver or if they are of the first type, they just transit through your city. Tips on how to handle these types of vehicles are below and will be explained further in the next part of this guide.

2. Delivery trucks/vans originate from industrial buildings inside your city, and are not to be confused with delivery trucks and vans coming from the region(entering the city by a highway or cargo station). There are two types of these: city delivery and exporters.

City delivery trucks will start at a farm, ore mine, oil field etc. (specialized industry type 1.) . and transfer raw products to a meat processing plant/mill, smelter, oil refinery etc. ( specialized industry type 2.) Next in this chain are new delivery trucks that spawn at those specialized industry buildings and transfer products to generic industry buildings(the ones that produce goods).


At those buildings(generic industry) delivery vans will spawn and transfer goods to commercial buildings for sale. If any of these buildings, in this production chain, don't have a place inside your city to transfer their load to (raw products, products or goods), they will then spawn as exporters. These look for a route out of your city to the region.

This can be a highway or any cargo station ( train, harbor, airport ). These vehicles are counted in the Outside connections info view panel (export). Tips on how to handle these types of vehicles are below and will be explained further in the next part of this guide.

3. Cars, personal transport of Cims. First time you can see a car is when a new Cim is moving in to your city form the region. Next time you see a Cim using a car it might come to you as a surprise to see them spawning a car in front of them. It's called a "pocket car". For convenience sake Cims have the technology developed by Capsule Corp. right out of Dragon Ball(manga).

This allows them to drive to and from any place they chose to, provided there are roads to drive on. Because you can't micromanage a Cims workplace, it is inevitable, that as your city grows, and the maximum distance a Cim will walk is exceeded, they will start to use Cars, adding them to the traffic on your roads, to get to those far away workplaces or education buildings. Tips on how to handle these types of vehicles are below and will be explained further in the next part of this guide.

4. City services spawn a LOT of vehicles. Garbage disposal, Firefighters, Healthcare, Deathcare and Police to name just the main ones. While there are green overlays placed onto roads when you are choosing where to build a city service building(hub), showing where their vehicles will reach and specific service be available, this isn't a line in the sand. Vehicles will travel farther than shown and try and do their jobs.

A small city has a few of these buildings, and each spawns from 5-20 vehicles. While a large, huge city might have hundreds of these buildings which makes for thousands of city service vehicles. Some of these vehicles do have special rule-sets, and can brake driving rules as they speed towards where they are needed. But, their numbers are many while the road space to fit them all is too small. And once they get stuck in traffic there are no new vehicles that can be spawned and sent to do their job instead of them.


They have to find a way of getting to their objective and if they can't the objective will not be accomplished. This is one of the main reasons why cities fail as a traffic jam "captures", "snares", these important, non interchangeable vehicles. See(read)*. Tips on how to handle these types of vehicles are below and will be explained further in the next part of this guide.

Tips and notes

Before I write tips on how to handle these types of vehicles:
Two additional notes:
The game has a built in system of teleportation for vehicles. Not all, but some types, like delivery vans and trucks. This allows for instantaneous transportation of products and goods between industrial and commercial buildings, called despawning. This teleportation can be turned off with mods. When a delivery van's time runs out it will be despawned from the roads and his cargo teleported to it's destination. You can test this by turning despawning off, waiting for commercial buildings to have a "no goods to sell" sign pop up, and then when you turn on despawning once again those signs are going to disappear in moments.


On top of that there is a hard limit on the number of vehicles that can be spawned in a city map at one time. This number can be viewed using mods, and it is about 16k. Once this limit is reached imports start to teleport to generic or specialized industry buildings as well as goods to commercial buildings(if you are importing goods). Not all of it, but what can't be spawned into vehicles. Cims also use this function to great effect when going to school or work. So while you might make a fantastical public transportation system it won't be used as much as the teleportation system.

Now for the tips, and these are just some of them, more will be in the next parts of this guide:
1. To help regional transiting vehicles pass through your city, without adding to your traffic, make sure to have simple, fast and direct connections between two highways which where not connected to each other before you made your city. Ideally a underground highway before or after the cities entrance.

2. To provide importers, both trucks and delivery vans with direct access to their delivery objectives you need to watch your Outside connections info view panel and be aware what you are importing. If it's goods then you need direct connection from a highway or cargo hub to your commercial buildings. If you are importing products(forestry, agriculture, ore and oil) then you need a direct connection to those buildings which are the objective of the importers, generic industry or specialized industry

3. If you are exporting goods or products you need the same things like above, just in the opposite direction so that exporters can exit your city, and the map, as quickly as possible, and with the shortest travel time.

4. If you are producing goods locally, and making sure to add new generic industry buildings as you add new commercial buildings the you have enough to supply your demand locally. But, to deliver those goods from generic industry to commercial buildings you need to make direct roads possible or create these zones next to each other.

5. Making a city that has all specialized industries(type 1. raw products and type 2. manufactured products ) as well as generic industry (making goods) will reduce the level of traffic coming in from the region. But, it will increase the amount of inner city traffic. Once again, careful zone placement of vehicle spawn points next to their objectives will reduce overall traffic and vehicle travel time.

6. Main ways of dealing with Cim's "pocket" cars type of vehicle are public transportation, pedestrian paths and RCI zone layouts that provide work, education and shopping next door to Cim's place of residence.

7. Cities services vehicles require a more micromanagement approach. Not only do you have to
plan out specific unzoned roads for easy and fast spawning and travel of these vehicles but you also need to take the specific service overlay and building influence distance with a large grain of salt. As the green effect of a building over roads isn't an exact view of a building's, and it's vehicles, area of effect.

These buildings also allow for a large amount of micromanagement with their budget as lowering or raising it will decrease or increase the number of vehicles they spawn. You don't always need the maximum number of vehicles on the roads, and the buildings them self's will reflect this dynamically as they spawn or despawn vehicles deepening on the need of that service.

But when you have large traffic jams, and you see in them large numbers of service vehicles just siting there unable to move, it is somethings better to simply reduce their vehicle count, wait for your other actions to reduce the traffic jam further and then let the remaining service vehicles do their jobs. Add more vehicles as the need arises so you roads aren't filled with extra vehicles which make the problems worse instead of better.

8. When moving from a few thousand Cims city to 20k,30k-50k+ Cims city you are faced with the hardest traffic as you can easily reach the games limitation of 16k vehicles while having minimal amount of roads and highways to put all those vehicles on. The volume of traffic on a low amount of roads and highways is what makes those midsize cities grind to a halt in one large traffic jam.

To avoid this build loads of excess roads, double up on one way two lane roads, have multiple connections between each city zone and enough distance to create enough road space to fit all the spawning traffic. This will give you just enough breathing room to push past 50k Cims to 100,200k after which the roads and highways become free of traffic jams as there isn't any longer enough of vehicles to jam them up.

9. More in part #2.

Thank you for reading or watching, I hope I was clear and to the point, and that this will help you in making great cities. Best of luck, Peter

Part #2 AI traffic logic, lane usage, path choice

This second part is going to be about AI traffic logic, lane usage and path choice and the rules behind them will help you build better cities, and manage traffic more easily.

Text or video, pick your media of choice:

The short story of Lane Usage

The short story is this:
The main problem we all have are the traffic jams created when the vehicles in our cities fill up our road capacity to the point that the traffic flow comes to a standstill. And to our amusement, horror or annoyance they do this by filling up only one lane out of two out, or out of three or even out of six lanes. If you want to find out what makes up for such a high traffic volume, read up on the previous part of this guide which is about vehicles.

This single lane pile up is enough to paralyze our road network and wreck our cities because of multiple problems that arise from vehicles not getting to their destination. This makes a lot of players conclude that the traffic AI is incapable of using more then one lane and that anything more then two lane roads are a waste of money and space. However, this is not the case, as I will write down below.

The regular gameplay starts of vehicles on the regional highway entrances on multiple lanes, which shows us that the traffic AI is capable of utilizing all lanes of a road, in this case the highway. All the vehicles coming in from the region have already planed out routs which include roads which they will drive on, lanes on those roads that they will drive on and places where they will change their lane to be able to turn from a multi-lane road to another road. This last part of their plan, the lane from which they will turn into another road is where all our problems come from and where player frustration is created.

What you must understand to be able to solve this lane usage problem with the traffic AI is that his actions are directly influenced by the white arrows, lane direction arrows, on the roads and highways themselves. When playing with no mods you have to use some creative means to change the way these arrows work in order to make paths that the traffic AI will use in it's calculation before it spawns a vehicles that is going to use that path. The only way to change a traffic lane arrow, when not using mods, is with the road that comes after it, more specifically, the lane onto which this arrow leads to. So while lane arrows control traffic you can control the traffic arrows by how you lay down each next consecutive road segment.

If you want to stop a lane from being a forward AND turn lane you have to add new road segments after it to influence the arrows on that part of the road/highway while at the same time adding new road segments to the side of that lane and a sort of a dead end road a bit farther off in the distance from the main road. By using this combination of a dead end road with roads that lead to and from this main road you change the arrows on the end segment of the main road and with that change the whole usage of the lanes.

This is a road design that forces traffic to use all lanes by making sure arrows on the lanes give vehicles only one option for travel to their destination. Each road that leads away from the main road creates road rules(arrows) that in turn force traffic to their one option for travel. Green is for traffic turning to the road in industrial area. Blue is for delivery trucks and city services to the Commercial area. And the Red is for vehicles exiting the city. The yellow circle marks the dead end of the main road(highway) which doesn't have a destination but gives other roads the ability to change it's lane arrows, it's rules.

The long story of Lane usage:

The main problem we all have are the traffic jams created when the vehicles in our cities fill up our road capacity to the point that the traffic flow comes to a standstill. And to our amusement, horror or annoyance they do this by filling up only one lane out of two out, or out of three or even out of six lanes. If you want to find out what makes up for such a high traffic volume, read up on the previous part of this guide which is about vehicles.

This single lane pile up is enough to paralyze our road network and wreck our cities because of multiple problems that arise from vehicles not getting to their destination. Like not enough goods for commercial buildings to sell, not enough products for industry to create goods out of or dead bodies not being picked which leads to the abandonment of residential buildings. All this makes a lot of players conclude that the traffic AI is incapable of using more then one lane and that anything more then two lane roads are a waste of money and space. However, this is not the case.

A note here:
The game has a built in system of teleportation for vehicles. Not all, but some types, like delivery vans and trucks. This allows for instantaneous transportation of products and goods between industrial and commercial buildings, called despawning. This teleportation can be turned off with mods. When a delivery van's timer runs out it will be despawned from the roads and his cargo teleported to it's destination. You can test this by turning despawning off, by using a traffic mod, and waiting for commercial buildings to have a "no goods to sell" sign pop up, and then when you turn despawning on once again those signs are going to disappear in moments. This can lead players to think their traffic solutions are good enough, and they are, but only once vehicles start to despawn to clear up the traffic flow.

The game has a lot of choices when it comes to road types. Along with the highway and highway ramps, there are two, four and six lane roads and two and six lane roads also have one way variants. This amounts to a lot of lanes for traffic to drive on. The regular gameplay starts of vehicles on the regional highway entrances on multiple lanes, which shows us that the traffic AI is capable of utilizing all lanes of a road. All the vehicles coming in from the region have already planed out routs which include roads which they will drive on, lanes on those roads that they will drive on and places where they will change their lane to be able to turn from a multi-lane road to another road. This last part of their plan, the lane from which they will turn into another road is where all our problems come from and where player frustration is created.

What you must understand to be able to solve this lane usage problem with the traffic AI is that his actions are directly influenced by the white arrows, lane direction arrows, on the roads and highways themselves. When playing with no mods you have to use some creative means to change the way these arrows work in order to make paths that the traffic AI will use in it's calculation before it spawns a vehicles that is going to use that path. The only way to change a traffic lane arrow, when not using mods, is with the road that comes after it, more specifically, the lane onto which this arrow leads to. So while lane arrows control traffic you can control the traffic arrows by how you lay down each next consecutive road segment.

Usually when you add a new road to an existing one, the arrows, which where simple forward pointing arrows, will get an additional part which will signal the possibility to not just drive forward on that lane but to turn from it. And it is because of this default behavior the most lane usage problems happen. The traffic AI is all too happy to only use that single lane which give the vehicles it spawns the possibility of not only driving forward but also turning when it needs to from that lane. Other lanes, with only the forward pointing arrow become less favorable lanes as they are limited in their possibilities. This is where you have to step in with some tricks to change these arrows forcing the traffic to follow your designs for it's path.

If you want to stop a lane from being a forward AND turn lane you have to add new road segments after it to influence the arrows on that part of the road/highway while at the same time adding new road segments to the side of that lane and a sort of a dead end road a bit farther off in the distance.


By using this combination of a dead end road with roads that lead to and from this main road you change the arrows on the end segment of the main road and with that change the whole usage of the lane. Because the end arrows give the lane it's usage, and with your direct control of the usage you gain the control over traffic's(vehicle's) lane usage. Vehicles have to obey the arrows on the lanes, it's how the traffic AI spawns them, with preset rules and drive path, and with that you gain full control through lane arrow modification.

Example of this lane usage problem

A typical example of this lane usage problem at a regular highway city entrance/exit. Each vehicle has a, let's call it a drive plan, and it's last stage looks like this: IF equal or closer to a distance of X to the turn leading into another road(an intersection) THEN turn into the lane that has a direct turn into that next road. More on this below, but before that a simple change to making road and highway connections that will unlock the potential of multiple lane usage.

A normal looking intersection made with one way roads(can be a combo of highway, highway ramp and roads) would look like this:

```````````↓ highway ramp
```````````↓
``````````→==============→
``````````→==============→ highway (or other roads)
``````````→==============→
``````````↑↑
``````````↑↑ two lane one way road


And how would vehicles(represented by O ) use the lanes on the highway? Like this:

```````````↓ highway ramp
```````````↓
```````````→OO======================→
```````````→OOOOOOO=OOO=OOO=OOO→ highway (or other roads)
```````````→O=======================→
```````````↑↑
```````````↑↑ two lane one way road

or even worse:

``````````↓ highway ramp
``````````↓
```````````→OOOOOOO=OO=OO=OOOO=OO→
```````````→OOOO=====================→ highway (or other roads)
```````````→OO========================→
``````````↑↑
``````````↑↑ two lane one way road

But with a minimal modification you can get traffic that uses all lanes equally

```````````````````````↓ highway ramp
```````````````````````↓
`````dead `→============================→
`````````````→============================→ highway (or other roads)
`````end```→============================→
`````````````````````````````````````↑↑
```````````````````````````````````` ↑↑ two lane one way road


and the vehicles are going to use the lanes like this:

````````````````````````↓ highway ramp
````````````````````````↓
```````dead `→==O==O==OO==OO==O==O==O==O==→
```````````````→====O==O==O===O==O==O=OO===O==→ highway (or other roads)
````````end``→==========O===O===O===O==OO===→
```````````````````````````````````````↑↑
```````````````````````````````````````↑↑ two lane one way road

Highway lane usage

Now back to a regular highway city entrance/exit, which graphically looks like this(where X stands for the lane change spot):

==X==============→
==X==============→
================↓→
````````````````ramp off ↓


what you can end up with this behavior is this, where O represent vehicles:

OOOOOOOX===================→
OOOOOOOX===================→
=======OOOOOOOOOOOOOOOO↓→
``````````````````````````````````````ramp off ↓

I have no doubt you have seen this on the entrance/exit from your city and it drives you nuts.
This would of course be terrible as vehicles would be using all lanes, and would only go into their turn lane, just before their target intersection, which would end up blocking off all the other lanes while vehicles are waiting to get into the lane from which they can turn. So to prevent this from happening, vehicles X distance is quite a large number. Which now leads to this:

O====X====O=====O==O======O=======O=====O======O===→
===O=X==O===O===O===O===O=====O===O===O===O===O===→
===O=O=O=O=O=OOOOOOOOOOOOOOOOOOOOOOOOOOOO↓→
````````````````````````````````````````````````````````````````````````````````ramp off ↓

It's an improvement for the traffic that doesn't want to turn here as there is a longer patch of a single lane that turning traffic has to pile on leaving the other lanes open for passing vehicles. So this works right? Only if you have this long patch of a single lane uninterrupted by other turn lanes. So what happens if you have several turn lanes close to each other? Like this:

==X===============X==================X==================→
==X===============X==================X==================→
=============↓→==================↓→===================↓→
```````````ramp off ↓```````````````````````ramp off ↓````````````````````````ramp off ↓

Well, this happens:

====X====O==============O===X===OOOOOOOOOOOOOOX===============→
===X==OOOOOOOOOOOOOOOOOXOOOOOOOOOOOOOOOOX================→
OOOOOOOOOOOOOOOOOOO↓→==OOOOOOOOOOOO↓→==OOOOOOOOOOOOO↓→
`````````````````````````````````ramp off ↓```````````````````````ramp off ↓`````````````````````````ramp off ↓

Does this look familiar? It does because we are back to square one. The length of road we had before, for the pile up to happen, is no longer available and the pile up spills over to the other lanes, stopping the traffic flow. The question here is why do we have so many off ramps coming from this highway so close togged and why are they all on the same side? The answer is: There is another highway going in the opposite direction right on top of this one, preventing off ramps going up. Like this:

```↑ ramp off
←↑======================
←====================X==
←====================X==

==X====================→
==X====================→
======================↓→
```````````````````````````ramp off ↓


Your next question here should be: "Why must this be like this?" And that is a great question because it's answer is: "It doesn't have to be like that". You can change this to suit your cities needs, your are not locked in. While highways might look almost like 6 lane two way roads their are not, because they are separate 3 lane one way roads. And as such can be moved to fit your cities needs. Now we can do something that will allow the traffic/vehicle AI to plan out his routs using more lanes.

```````↑ ramp off```````````````````````↑
==←↑====================↑==
==←==================X==↑==
==←↓====================↑==
``````↓````````````````````````````````````↑
``````↓````````````````````````````````````↑
``````↓tunnel or overpass```````````↑``tunnel or overpass
``````↓`going down````````````````````↑```going up
``````↓````````````````````````````````````↑
``````↓````````````````````````````````````↑
===↓=====================↑→==
===↓=X====================→==
===↓=====================↓→==
``````↓````````````````````````ramp off ↓


Once you break out of the previous pattern you will see that you can make a lot of new ways for traffic to get off/on your highways and enter or exit your city. These tunnels or overpasses can go in every direction and from every side of both highways. The only rule you have to follow is to have and exit before and entrance. So that the vehicles that come onto the highway wouldn't get tangled into vehicles trying to get off the highway.

But the most important effect this has on the vehicles traveling on the highway is that they no longer use just one lane to get off the highway. They use two, while the middle lane becomes this travel lane which makes it super easy to move to ether side for the next exit, or move on it after an on ramp to the highway.

You can see this design in use in this video:

Tips and notes

Before I write tips on how to handle these types of vehicles, a note:

Vehicles trying to drive from one location to another will select their route, including the choice of lanes, at the outset of the journey. This route is always the fastest legal route. This calculation assumes that the vehicles will be able to travel at the speed limit of every road segment, i.e. it takes no account of other traffic. This is usually, but not always, the shortest route - vehicles may choose a slightly longer route if it travels down higher speed limit roads.

Vehicles will not change their planned path, or even their planned lanes, if they encounter traffic. Vehicles will only change their journey plan if their route is made impossible by changes made to the road network while they are en route. Because of this behavior, a new route for traffic to bypass an overloaded intersection will only function as intended if, irrespective of traffic, it represents a quicker route. Since entire routes are pre-planned, a newly constructed road may not see immediate use. Source: https://skylines.paradoxwikis.com/Traffic

Now for the tips, and these are just some of them, more will be in the next parts of this guide:
1. Use highway off ramps to direct traffic from a highway to other roads or highways by connecting those points with ramps. As the highway has 3 lanes, you can make 3 highway off ramps from it. Each highway ramp needs to connect to a different road to force traffic that comes to these intersection to chose a specific ramp(single lain) and to continue it's path on it. This way you are forcing the vehicles to pick a lane, from the start of it's journey that is the only lane to it's destination over that part of the road. This prevents the vehicles from interfering with each other and switching lanes on a busy highway blocking each other.


2. Using 6 lane one way avenues is great, but only on parts of the city where you have many intersections that have roads leading away and into that one way avenue. If not, a two way one way road will do just fine.

3. The more one way roads you use, the easier it is to force traffic into specific paths that will take it to it's destination without messing up other vehicles paths.

4. With one way roads and specific lanes from spawn to destination you can make cities that have zones which send vehicles to each other(I to C, R to I etc.) be more far and spread apart. Making exclusive paths with specialized lanes helps speed up traffic, stops lane changes that block paths and provides more options when designing cities.

5. When adding roads or highway ramps from a highway sometimes you won't even see a change in the lane arrows. The arrow will still show only a forward point even with a new road that requires a turn arrow to be added. This is only a visual glitch as you will actually see vehicles make that turn.

6. Always make sure that when you add a ramp ONTO a highway it isn't immediately followed by an OFF ramp. Make OFF ramps before ON ramps, you need very little space after the OFF ramp. But leave a lot of space open after an ON ramp before making an OFF ramp. This prevents vehicles from getting into each others way as they go ON and OFF the highway.


Thank you for reading or watching, I hope I was clear and to the point, and that this will help you in making great cities. Best of luck, Peter

Part #3 RCI zone design

This third part is going to be about RCI and O zone design and how it creates traffic problems, while it can also be the solution of those problems if applied properly.

Text or video, pick your media of choice:

The short story of RCI zoning

I am going to show you all the ways your zoning choices affect the future traffic situation of your city. Planning out the RCI which is short for residential, commercial and industry zones is not something players take seriously enough. I am going to show you several types of RCI zoning and explain how their design directly impacts the traffic flow of your future city.

Now let’s dive into the 3 main ways you can zone RCI in Cities: Skylines and what that means for future traffic flow. As a bonus, the last part of the guide will showcase the most advanced zoning designs and the ones that can prevent most traffic problems.


The first design I am going to show you is what most Cities: Skylines players create, or at least try to, until the traffic nightmare that is produced by this design completely breaks down their city. This is what I call the "Exclusion" RCI design.


What I mean by this is that players create these large areas out of one zone type. They first create a residential zone as this is what you start any city with. Then they make another zone, this one dedicated to commercial zoning and keep it separated and off the residential zone.


And the last nail in the coffin of this design comes with the introduction of another exclusive zone, this one dedicated to industrial all the way on the other side of the city, as far from the residential area as possible and next to the commercial zones.

There are multiple things wrong with this zoning approach and I will explain them as I show you the simple evolution of this design into an actual working and proper RCI design.

Long story on Zoning and traffic

The long story is this:

As you read in the first part of the guide, besides vehicles created by the region in which your city is, all zoned buildings create vehicle traffic as well. These vehicles make up the inner city traffic between different zones and those zones and the region. The first two parts of the guide give good tips on how to deal with the vehicles coming in and getting out of the city, or going from one end of it to the other. This third part will focus on the inner city vehicle traffic while also giving pointers to how different zoning designs influence the outer city traffic.


In basic terms inner city traffic is added to every time a zoned building spawns a vehicle whose destination is another zoned building in the city. And it is subtracted from every time that vehicles gets to it's destination(no mater does it get there by teleportation or not). The main problem here is the fact that the spawn location buildings never stop spawning new vehicles, if they are operating normally. Mostly the Industry has this problem.


They keep adding vehicles to the inner city traffic 24/7/365. But as traffic gets more jammed up, fewer and fewer vehicles get to their destination, get subtracted, before another vehicle is spawned. This creates a constant increase in the number of vehicles on the streets which is its own problem, root cause. Add to this the vehicles route length which makes the problem worse the longer it is.


Besides Industry zones, Residential zones create vehicles, more precisely, Cims themselves do with their pocket cars. If they need to go to a far off place to shop or work they walk out of their zoned building and spawn a vehicle for them to use. Public transportation helps with this but not enough to solve the problem of too many vehicles for the street capacity.


Commercial and Office zoned buildings don't spawn vehicles but they present destinations for them. Commercial zones have delivery vans, workers and shoppers coming in. While office zones have just the workers whose vehicles have them as their destination.


Now that we know all of this we can see which zones need more highway connections, which fewer, which zones have more and which fewer destination in which zones:

1. Industry zones need highway entrance and exit for its trucks that import/export. They need road connection to Commercial zones for its delivery trucks to bring goods for sale. They need a way for workers to get to their jobs in the industry.

2. Commercial zones need a connection to the highway only if goods are imported instead of made locally. They need a road connection to Industry zones for goods deliveries. And they need a road connection to Residential zones to have shoppers and workers coming in.

3. Office zones just need the road connection to Residential zones for workers to come in.

4. Residential zones need a highway connection for Cims to move in our out. They need a road connection to every other zone so they can work or shop in it.

This tells us that R zones create the most destinations and are the most diverse, but they are also the zones that have the most option besides spawning vehicles. They can walk or use public transportation to their destinations. They are also the lowest priority for the engine when it allocates the limited vehicle slots, as they are teleported left and right, while they don't really care if they are late to work.

This is why Office zones never have any problems no matter the traffic conditions. (I am leaving out the problems with services vehicles here as they are not the problem just the symptom of one)

Commercial zones don't have problems with workers, as they will get to work when they get to work(Cims really have it good), only a bit of a problem if shoppers are slow to get to them(not enough buyers problem message), but a very big problem if goods delivery vans are not getting to them to bring goods for sale. This impacts the taxes collected as well as it leads to abandonment.

And finally Industry zones. The biggest problem makers of the zoned buildings. They are all both target destinations and vehicles spawns. Workers getting to them isn't too much of an issue as previously explained. But the import, transfer of products and the export/transfer of goods is the biggest problem here.

Generic industry buildings, the ones that produce goods need their products for manufacturing while they send out goods, in deliver vans to Commercial zones or the region if they are exporting. Specialized Industry zoned buildings follow the same pattern only difference is that the destination are not Commercial zones but Generic industry buildings or the region exit when exporting.

Here is a video that gives some tips on how to zone on roads to give yourself more room for traffic to flow.

Tips and notes

Now that we know the interplay of these zones, when it comes to traffic, we can take a look at some of the basic, most used zoning designs and how they work or fail at working. And after that some more advanced zoning which deal with traffic a lot better.

First off, separating the workforce from their jobs, the R zones from the I zones is a bullet proof way of creating extra unnecessary traffic. To work in factories Cims need to get to them. Placing these workplaces in an industrial area on the far side of the city just creates a long commute for the workers forcing them to use cars and/or public transportation.


The same goes for C zones as they are visited by both workers and shoppers doubling the amount of Cims which travel back and forth from them.

Note:
Cims and their usage of cars and public transportation isn’t your only concern when it comes to vehicles creating additional traffic volume. A large portion of the traffic volume is created by the delivery vans which are spawned at industry buildings and deliver goods to the commercial zones.


In case you don’t have enough local industry, the generic type, which produces goods, these have to be brought in from the region by highway, railway or other means. This creates many vehicles which have long commutes between their spawn point, destination and their despawning point. This is something you can easily avoid by doing two things.

First you zone C and I in such a way that commercial buildings are practically next door to Industrial buildings. And you make sure that you can produce all the goods your C zones use up locally, by zoning enough generic industry buildings to make it.


Note:
The game’s AI is smart enough that it will send out goods produced in an industrial building to nearby commercial buildings which sell it, thereby reducing travel time of the delivery trucks to a fraction of the time they would need if they had to travel from another part of the city or come in from the region.


Now I know you might be worried about ground and sound pollution. But you need to realize
that commercial buildings never have a problem with ground pollution.


It doesn’t register to them as a danger to workers or shoppers. That is why it is completely safe to place C zones right up against I zones and why I think the developers intended for RCI mixing to be a very efficient city design.

By incorporating the C and I zones into your R zones you all but remove two out of three sources of high volume traffic. Sim cars and delivery trucks.

You are left with the large trucks and tankers which deliver products to generic industry buildings which use them to make goods. These products you can make by yourself in specialized industry buildings, which in turn need raw goods created by industry buildings zoned and constructed on resources like forests, fertile land, oil and ore.


The point here is that even those specialized industry buildings are constructed door to door. When you zone specialized industry on a resource you don’t just get raw product producers but also raw product users which create the actual products the generic industry uses. It’s another example of the Developers themselves pointing to us, the players, that certain buildings should be constructed right next to each other so that their production chains would deliver to each other instantly and without long distance transportation.


So, by creating this chain of raw product, product, goods inside your city and reducing delivery travel time to a minimum you also reduce the number of active vehicles on the roads, at any given time, to a minimum. And by having generic industry buildings dispersed across the city and next to commercial and residential buildings you reduce the density of traffic overall which prevents traffic jams from ever occurring.


In essence, you eliminate the cause of bad traffic which is way more productive than spending hours and hours in thinking up traffic road and highway patchwork solutions which never solve anything because the core issue is not addressed.

Now I want to show you the fourth zoning design which isn’t too different from the third one but it has some important, game improving aspects.


The changes to the design are firstly in the fact that not only do you have C zones right next to I zones but also some of those C zones are embedded deep into the R zones. This is a good thing, even if it does create some longer delivery van routes because it gives Cims more options for shopping and gives walkers, Cims who don’t use cars or public transportation, shops which are right next door. You basically switch one delivery truck for dozens of cims personal car rides especially in high density zones.

Second very obvious redesign is the choice of zoning on only one side of the street. You can accomplish this by placing roads one right after the other in a specific chain and separated by 5 zonable squares distance. This will let you choose which road is going to be zoned and which side of it by 4x4 buildings.

Once you choose a side it’s important to keep using the same side on each consecutive road. This instantly reduces the amount of traffic which flows in any street zoned like this and gives you double the road surface for vehicles to travel on, reducing overall traffic volume in the city.

Some might argue that this creates a great number of additional intersections which is bad for traffic flow, but what you have to keep in mind is that intersections are problematic only once they have too many vehicles entering them at the same time. If you have doubled the road surface by using this design you have also reduced the amount of vehicles at the intersections by half.

Extra tips

Another addition are the pedestrian paths going from one street to the next connecting different residential zones and giving Cims access to streets and buildings which would otherwise be outside their walking range.


A bonus here is that these paths spend one or two zoneble squares and further move away the R zones from places where there is ground pollution and also from places where there is sound pollution from the C zones. The sound pollution can be additional buffered by placing Office zones between C and R zones. Just as C zones don’t care about ground or sound pollution, office zones don’t care about noise pollution and don’t emit any, letting Cims enjoy the peace and quiet of their homes.

On top of all of this, setting up pedestrian paths which cut through entire zones allow you to freely disable pedestrian crosswalks on roads. This further reduces vehicle travel time in the streets, again directly impacting your traffic flow. But for this to work you must place pedestrian tunnels or raised paths over the streets. This is totally up to you, as it is just a bonus design, not entirely necessary. This totally made my road spiral idea go from a theoretical concept to a working Spiral City when I created it in my Designing new Cities Let’s play.



If you want another way to reduce cims reliance on vehicles you can make this design in precise ratios of RCI so that you have just enough cims living in a neighborhood to employ all of the in the near by C and I zones so that they have jobs in the walking distance from home and so very little reason to use cars or public transportation.

Note:
Buildings on different levels of their development require or house different numbers of Cims so this ratio is dependent on the level of the buildings inside one neighborhood.
Using the ban heavy traffic district policy is also very useful here as it allows you to prevent trucks carrying products from taking shortcuts through residential areas and forcing them to use the roads, avenues and highway ramps you have designated for heavy traffic which lead them directly to industry buildings which need those product deliveries.


Of course this is not the only way to mix RCI and O zones. You can come up with your own ideas and designs but the underlying mechanics stay the same. By zoning properly and making paths and routes shorter for every type of vehicle and Cim in the game you can manage traffic in such a way that you won’t ever have to deal with traffic jams or a myriad of other problems which show up as a result of them.


Thank you for reading or watching, I hope I was clear and to the point, and that this will help you in making great cities. Best of luck, Peter

Part #4 Highways - city's regional connection (entrance)

It all has to start somewhere, and indeed in this game a lot of the traffic problems start at it's entrance. Even if you have read and used all my advice from the previous three seconds of this guide, you will still see traffic jams on the entranced to your city unless you add more of them.

I am going to show you how to go from bottlenecks like this:

into highways like these:

This which will allow your traffic to move beautifully.

The first example I showed you is the basic setup that a lot of players use in game, which is an already made solution for getting traffic into and out of the city.

The problems with it are it's limited number of turn lanes, highway ramps, the size of it, and the need to place it over and over again to give vehicles multiple entrance points to both sides of the highway.


Now let me show you how to ditch this design for something far more flexible, more easily placed and totally customized.

The "Tree" highway design.

A full video explanation can be found here:

The way you make this "Tree" highway design is by first deleting and then spacing out the two highways.


Then you are able to place off ramps in both directions away from each highway because there is room for them now, compared to the original highway design.


If you need to you can also raise these highways and use ramps down and up to connect the city to them while having intercity roads underneath which won't interfere with the highways.


To make even more use out of this design, you can crate long underground or above ground ramps which will lead the traffic directly to the main parts of the city. Or industry, or commercial, which ever place needs to import products or goods and so remove the need for those vehicles to move around the city. This way they get where they need to go directly.


A very important point here is the way ON and OFF ramps are placed. You NEVER want to follow an ON ramp directly with an OFF ramp. Because the vehicles moving into their turn lanes just before the OFF ramp will run into he vehicle coming onto the highway to that same lane.


You want to always follow an OFF ramp with an ON ramp.


Another way you can design it:


If you can use the mod Traffic Manager Stable Edition in your game than I will recommend to you to use the tips from this video.

This traffic guide explains the problem of vehicle lane switching in Cities: Skylines and gives solutions to make your highways free of traffic jams. It shows how to use a mod called Traffic Manager to fix this problem, with only a single option from it’s toolset, which is powerful enough to fix several problems like lance changing or slowdowns at off ramps. For console players there are other ways of achieving similar results using tips from the video below.

Link to the mod on Steam Workshop : https://steamcommunity.com/sharedfiles/filedetails/?id=1637663252

A compact interchange design

Here I will show you an efficient highway interchange which takes very little space and takes into account every path vehicles might want to take when 4 highways meet at an angle.


The design is straightforward. The aim is to have each highways left and right lane send vehicles to another highways left or right lane while also taking vehicles into it's right and left lanes.

You can see the whole build explained step by step in this video:

This is achieved by first bulldozing the old highways and placing new ones, but with more space in between them for the new ramps and tunnel entrances/exits. The other two highways are built almost identically with the only difference being that these are raised up one level. They will cross the original two highways.


After that is done you place your camera above one highway, and start making ramps to it's right hand neighbor.


You keep doing this for each of the highways, making sure to connect them so that one has an OFF ramp to the right, which becomes an ON ramp for the outer most lane on the next highway.


Next step is to make tunnels from the left side of each highway, the left lane, which now becomes a turn lane into that off ramp tunnel.


This tunnel needs to connect the the highway which runs perpendicular to the highway from which the off ramp started and become an ON ramp to that highways left side.


If you have any trouble connecting to the highway with that on ramp from the tunnel, start by making an OFF ramp from the point onto which you wanted to connect the ON ramp to. Connect the two and change the direction of the last piece.


Now you do the same with the other highway and it's perpendicular one. When you have to intersect two tunnels then you use the second tunnel level on the new tunnel to go beneath the first one and then go back to tunnel level 1 and and dig up to level ground for the on ramp to the next highway.


If you don't have room to make the off ramps at the same spot, that is all right, you can do so a bit back, before the interchange.


You will notice that we are following the same rule as mentioned before in this guide. ON ramps after OFF ramps.

Make sure to connect all of those four underground ramps to each of the highways.


Now if we were just to leave this design at this we would still suffer from the games programming shortcomings and the vehicles forcing the usage of just one lane. This is where the traffic manager mode comes in with the lane customization opinion. The final step is to use the Traffic manager mod to manually connect lanes to each other so vehicles don't use a lane which is for turning as a lane to move forward.


You also have to make sure to prevent lanes from being used to drive forward if that lane is about to be connected to with an ON ramp from another highway.


And after you do all that, you will have perfectly used lanes on a small and compact interchange of 4 highways.


Thank you for reading or watching, I hope I was clear and to the point, and that this will help you in making great cities. Best of luck, Peter

[Work in progress] Part #5 Roads network design

under construction!

[OldBlueBen]

i needed to know that about on and off ramps, cheers.

[CoolantCorrie]

Very detailed, very helpful, thanks! I also build lots of footpaths and cycle lanes, if possible as a network (with elevated walkways and tunnels) and I start it alongside my first roads. I also build shops and jobs so that as many cims as poss are within walking distance - much of this actually taken from advice in your other guides. Thanks!

[Yumi]

Great work ;)

[我是一只笨的狗]

Nice guide thanks for sharing

[Kolchak]

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