Updated: August 22, 2018
Several months ago, I wrote my Good Traffic Guide, explaining the virtues of correct urban planning, and how to manage your traffic network flow efficiently. The article focused primarily on the roads and the use of roundabouts, as well as proper trains timetable. But it was also idealistic and expensive.
Since, I've spent a lot of time playing new scenarios in Cities Skylines, and consequently, developed an even deeper understanding for the game's mechanics and pathfinding algorithms. I also decided to experiment, with one main goal: reduce expenditure. I wanted to make sure, infinite money or not, that I had cities with a positive monthly budget, and the higher in the green, the better. Hence, this improved Better Traffic Guide.
Model 1: Train traffic only (external)
I am not the first - nor the last - person to try to nail down the perfect formula. And you must have heard about the trains-only idea. In a nutshell, you do not connect your industries to external roads, and you only use trains to ferry goods. Sounds like a nice concept. Let's explore.
I started by creating my urban area the usual way - long, six-lane roads, roundabouts, the usual deal. Then, when the orange bar spiked up, I began developing my industrial zones separately, without connecting them to either the blue-green residential-commercial zones or the highways leading outside the city.Now, this is not realistic, of course. There's no way that such a setup could exist in the real world. But Cities Skylines does allow that. City demand is global, and so you can have isolated pockets of different zones anywhere you like. It does remind me of Caesar III, which also allowed urban areas to be disconnected, so you could develop only small areas with patrician villas to avoid sudden explosion in unemployment leading to massive shortages in labor force.
You still need all the services to reach the industrial zones, though - again, much like Caesar. This means separate fire and police stations, separate garbage yards and incinerators, and maybe road boost facilities. Once that's ready, you have your rudimentary model in place. The only thing you need are cargo train stations to ferry the produce outside the city limits.
It works well - in the sense that it is cheap, easy to set up, and you will not have any heavy traffic clogging your urban areas. You will have a high overall road throughput (above 90%), the road grid will be green and maybe a little yellow, but nowhere will you have any red chokepoints. Trains will do their job, and you should be fine.
However, your commercial zones will suffer. Without adequate supply of finished goods coming from your industrial zones, they will never reach the highest level of development, resulting in somewhat lower taxes and land price. Effectively, you will be importing goods from other cities via your road network, possibly even the same goods you've just exported via train. It's not a bad compromise, but it's not ideal.
Model 2: Train traffic only (external + internal)
The improved version of the above system is to add a second internal train loop to your city. Essentially, your industries will deliver goods not only outside the city but also inside the city, to other cargo stations that do have a road connection to your green and blue areas. Trains will depart your train stations in the industrial zones, travel a relatively short distance to your inner city cargo hubs, and deliver the goods at these destinations. There, every time a train arrives, a series of dispatch vans will be generated at the cargo station, going into the urban areas, delivering the goods to different business. In a way, this is often how real-world traffic works, as goods are collected at large warehouses and transport hubs, brought in by ship or train or heavy trucks, and then distributed using smaller trucks and vans.
On one hand, this is as genuine as it gets. On the other, there are many shortcomings to this model, despite its realistic concept. Train management in the game remains tricky. New trains are spawned very quickly, and they will depart the station regardless of any so-called signals ahead, meaning you could have anywhere between one and a hundred cargo trains on your tracks.
If your source and destination cargo stations are relatively close to one another, you may very quickly end up in a situation where the tracks are completely jammed. I found out that I had to delete tracks, stations and/or divert trains to manage this. The smart system that controls the train traffic like in real life simply does not exist, and you will need to micro-manage.
You can somewhat combat this by trying to pair source and destination stations on 1:1 basis, but there's no guarantee this will work well, because the industry density is often not equal, and sometimes, trucks need different routes to reach the same station. This means some stations will be favored over others, purely based on the shortest path calculations, and you will still end up in the micro-management mess.
Another workaround is to distribute your internal cargo hubs around the city in a circle (loop) fashion, hence the word hub, right, sort of, yeah, but it is still not a perfect solution. Again, train stations close to the industrial areas will end up flooded with goods, while the remote ones will be somewhat starved, and you will have areas with heavy traffic and congestions, and then those without. This always happens with industrial zones, and it is unavoidable, but it becomes an even bigger problems when your industry does not have a direct connection to the urban areas.
The track jams can also happen on the outside connections. While my previous findings from the GTG still stand, there's room for improvement, mostly around where and how you place your cargo stations. A rule of thumb says you ought not to have more than one cargo station per outside connection, and that you should not mix cargo and passenger traffic. Easier said than done, of course.
Having fewer stations will limit how you shape your industries, and inevitably, you will end up with large queues of trucks waiting to unload their cargo at the few stations, and you will have to plan circular routes for your ingress and egress truck traffic. Not unlike what we had before, only now it happens in isolations from the commercial and residential zones.
The big issue remains: Train stations are single points (of failure) on your traffic map. So if you channel all your traffic there, you essentially force the growth and development of your city around them. The more you have, the more balanced and distributed your network is, but it is also costlier - essentially you have at least two stations per industry line (source and destination stations), which cost a lot, whereas road traffic is basically free. In addition to cost, you also end up with traffic jams, especially on shorter lines, which further constrains your city building decisions.
However, the model works fine - there's some element of distribution and balancing, plus managing clogged lines now and then. That said, I had good and consistent demand, and placing multiple stations around the city allowed for high levels of development, without any limitations. It's also an interesting departure from the classic, predictable scenario building, and it's life-like in how we do that in the real world.
Cities Skylines is a great game. But like any GAME, it has its quirks. While it's a very realistic title overall, it is also a pragmatic one. In other words, your computer does not have enough juice to make every little decision perfect, so the developers are cutting corners. Most notably, train traffic. And pathfinding, which is probably the most complex part of the simulation.
Then again, think of it as a challenge. It would be boring if things were predictable. So you play the game's inefficiencies and shortcomings against itself, and try to come up with an algorithmic solution of your own. I like the fact my mind keeps constantly imagining these other possibilities, and I still have a few new theories to explore. Which means hundreds and hundreds of hours more invested in this fun title. Indeed, that is not all. While I did touch on the wonders of train traffic, there's still more we can do. But that is the topic for the sequel, which will be named, yes, you guess it, the BEST Traffic Guide. So long.