You can skip this part and go directly to trains.

If you are reading this, you either have problems with big city trains or you heard of it and want insight on how to preplan your city.

Here's the problem.

In this game, every commute and deliveries are tracked. There is great attention to detail and it is this attention to detail that causes problems. In a big city, using simple rail networks, the trains will clog up quickly. This prevents deliveries of goods and raw materials to various businesses which lead to the death of your city. When it comes to automobile traffic, the game has a modest set of tools for which you can manage. As seen below by my high capacity highway interchange. It's not decoration, its utilitarianism.

Train networks are treated the same way as road traffic. In most simulators before this, the trains are merely an animation. But in Cities Skyline, the train carry goods, and if these goods are not delivered, THE WORLD ENDS....ahem....excuse me. Unfortunately, while train traffic is complex, the tool given to you in-game to manage this is rather simplistic. There are no signals, no policies and no one way routes for trains. This guide offers a few tips and considerations to deal with this mess.

Before we proceed, bear in mind that my solutions are applied to an old city. My first city. The city of novices and mistakes. It looks ugly, but that's not the point of this guide. Let's begin.

At the time of writing, train stations can only support two lanes. It isn't a representation of how real train stations work so we need buffering. Buffering allows trains to queue up without clogging the main line. As you can see from the picture, doing this will cause you a lot of space and may very well PISS YOU OFF. But think of it this way, it allows you to build cool convoluted train tracks. Now aren't you glad you bought this game?


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Now buffering has to be done right. Depending on the amount of traffic a station receives, it has to be quite long. Take a good look at the picture below. See the problem? Train A is trying to head south. But Train B is blocking the way and won't budge until Train C clears the tracks. This cluster F of trains has basically clogged up the main line. No one's going anywhere for a while and train operators are paid by the hour. We certainly cannot allow that.

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If you have limited space, your intersections has to be at least one train's lenght. As you can see now, the train heading south is waiting without obstructing the main line.
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The above solution only works if that particular station does not receive a lot of traffic. For really busy areas, you will need a longer buffer as seen below. Now my freight's can wait as long as they like since they won't be clogging up their main lines.

Now I know what you are thinking, MOAR TRAIN LINES? Yes, it's awesome isn't it? The Metro and Bus lines can only support so many passengers, eventually as your city grows, you will need to incorporate passenger trains into your mass transit network as well as to bring in more tourist. The problem is, you often have a lot of full size trains only carrying 1 passenger. So it helps to isolate passenger lines from freight lines as soon as possible. I try to do it at the city connection itself. The less trains that compete for space, the better.

Tourism are a massive source of income so there will be significant motivation to connect your passenger lines to the international network. From what I can see, a local line connecting two passenger stations will only spawn two trains. The problem arises when you have a large number of tourist trains clogging up the line. You could isolate it completely but this would mean having multiple train stations in your city centre. The trick is to keep the routes simple.

Just remember. Residents do not visit friends in other resident areas. They go to work, school and they go shopping. That's it. So route accordingly.
In this picture you can see a busy train terminal. Without freight trains to compete for space, the trains runs smoothly. However, I have a large population who wants to go shopping. So I need to double my train capacity. This is how I do it. The trains will arrive at the station and go back in the direction it came. The passenger lines are servicing two ends of a very large residential area. Naturally all my mass transit is centred on getting people to the train station. With less reason to drive, your services will work much better. And since I design the train stops to avoid through traffic, there is little chance for complications since the lines on each side is loaded independently. Fewer number of train stations also mean higher utilization rate.

There is particular satisfaction in seeing your mass trasit fully utilized.

At the time of writing, the game does not allow you to edit road connections outside of the city limits.
With my city, I am importing and exporting 35,000 units worth of stuff in equal measure. Disconnecting the city from international traffic is not an option as vast amounts of imports are required to keep the city going. However, the train line outside the city limits cannot cope with the traffic as seen in the picture below. At this point, I really won't mind if they despawn after leaving the city limits. But here's the solution. And yes, it involves MOAR TRAIN TRACKS. Awesome.
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The idea is to isolate your train traffic into their respective categories. Passenger lines, international traffic and local freight traffic. The idea while similar to isolating passenger lines requires a bit more tinkering for it to work. Most of you will get the idea from the picture below.
There are three things I would like to draw your attention to from the above diagram.

1. The international line is connected to the passenger line.
   
2. The City Freight Network is completely ISOLATED from both green and red lines.
   
3. Notice that the freight trains although connected to the passenger lines, have no reason to travel into passenger stations.

Now I would like to draw your attention to the white box in the diagram. What are they? Well look at the picture below. Due to experimental reasons, I've completely disconnected the passenger line from international route but I assure you it will work. As you can see, the international freight is not connected to the local network at all. Imports will be brought in, and the station will spawn their own trucks and ship it to the local station where it will be loaded to the local network for distribution. Brilliant! Inner city freight distributions will spawn a LOT of trains; this will make your train traffic a lot more manageable.
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This works. It works really well. And here is the proof. On the left, the freight truck leaves the international train station and on the right you can see it going into the local train station.
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• When you modify the network to this extent, chances are, there will be a few trains stuck in your train lines unable to get where they are going. You will have to remove the rails under them to force a despawn.
  
• Trains that were already enroute to your city will despawn when they enter. Only new trains will understand this new routing system.
  
• Since I have two habours in the city, I found that instead of going to my local network, some of trucks will use the habour to move my goods within the city. They will route to the local network once I disable the habours. This is interesting since the water ways never get congested.
  
• As you can see from my screenshots, this works perfectly fine without a valid road connection.
  
  
  Here's a chirp to the developers: Allow us to edit roads outside of city limits. Just prevent us from zoning of placing services. The whole map is rendered anyway, so I don't see why the restriction.
  
  Special Thanks to Azzarrel for sparking this idea.

Yes, isolating your city. That means NO ROAD connections between patches of your city. Your city becomes entirely reliant on trains to get around and with simple train circuits, it works really well. Here's an example.

In the picture below, you can see that the industry is running happily without any road access. You will also notice three train stations. There are passengers, international freight and local freight. You will need all three as well as duplicating essential services like bus depots, fire stations and police. This prevents vehicles from clogging up your otherwise already crowded highways.
In this particular example, I started a new city which relies on trains as a priority. I basically setup a starter city and removed everything once I had unlocked all my options and had enough cash. What I found was my local freight network was underutilized. This might be due to the fact that I had an exclusive highway network that connects industry to commerce. As far as industrial deliveries are concerned, I have very few highway and train intersections, so I can afford to dump more traffic into my train network as my city grows. It also allows you more control over the behavior of the train network.

Local freight train transferring materials between local industries.


So why stop at isolating your industrial zones? You can build a whole new city that is only connected by rail.
Two city one map

I believe this picture is self explanatory

You don't have to rely on this exploit for it to work. In this picture below, my freight terminal serves both commerce and the habour. Yes your blue zones will produce exports and require deliveries. The habour will generate a lot of truck traffic. So in this case, trucks that leave the habour is connected to a highway that goes directly to the industrial zone on the other side of the map. It's a long drive, I know.

You may think that this game does not incorporate accidents and disasters. Well it does, for trains anyway. You will notice from the picture below that my freight train has indeed had a bad day. It is something you should keep an eye on. So what happened?
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When you modify the line, all the trains affected actually stops to reconfigure their GPS, because you know....reasons. Cars do the same thing too. They will hapilly stop in the middle of the F highway to play around with their satnav. Because you know, it's not safe to drive while doing other things. But I digress.

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When updating their routes, some train operators uses iTrain-Maps, and like a famous fruit based satnav app, it sometimes direct them to the middle of the sea. For trains however, they get directed to hell. This actually affects traffic on the line and prevents delivery of goods. So my solution is to delete the line and wait for it to despawn, effectively sending it to hell. Good riddance.

This section answers one question. In my most humble of opinions, what is the perfect layout of a city.
Well, this. I believe, this monstrosity is as organized as you can get. It's not very inspiring and I rarely build like. It is also a bit hard with the tile system and locations of natural resources. And this is just an illustration, the porportion of zones really depends on you.

• It allows rapid delivery of raw materials and goods to retail and other industrial businesses.
  
• Residents may visit a great number of things, but as far as I know, they don't have friends, so you don't really have to unify a residence to residence connection.
  
• Offices insulate noise pollution from residential areas.
  
• Your mass transit becomes relatively simple
  
• Makes use of your trains ability to rapidly shuttle large number of residents.
  
• Can't think of anything else.

• You can't expand your commercial zones
  
• It's boring...maybe.
  
• Can't think of anything else.

Some of you may already know this but walkways are not decorations. They are the unsung hero of an efficient mass transit network. You will find residents do walk quite a long way to get to various services. And if like me, you have roads with very few intersections, you will find commuters will not jay walk even in the suburbs. So you need to build overhead crossings for foot traffic.
Well....maybe not like that...kinda violates a few health and safety laws there

Without nearby crossings, you will find overcrowded bus stops or unused metro stations. To make it worst, foot traffic will actually take the bus around your whole city just to get to the other side of the road. So make sure you plan footpaths ahead of time to avoid eye watering demolitions of your upgraded buildings.
Foot traffic can't use the metro on the other side of the street because they won't cross the road. My utilization spiked after moving the metro to the same side of the road.