SimCity Strategy Guides
This topic was originally designed to be much longer with examples of different basic road patterns etc, but to be honest I really couldn't find any that really worked with city-sized populations!
The following sections can be found in this article:
Getting the most out of your road network starts with dealing with the connection to the highway. Regardless of the arrangement of the highway exits in your city, you can reduce congestion by increasing the distance between the exit and the first junction. Avoiding 4 way junctions is a good strategy in general, but particularly on the connection to the region. I would also recommend not bringing streetcar avenues right up to the highway connection because it also puts an additional junction close to the busy exit.
Not zoning areas along the main exit route will help reduce congestion. Spread out buildings that generate heavy traffic (i.e. event centers, universities, tourist attractions, high density factories etc). Where possible keep specialization chains together, like storage depots, mines, factories etc. Ensure that roads where delivery vehicles interact with other city traffic is kept to a minimum. If you're relying on commodities trading for income then getting the upgraded trade port to ship goods by sea and rail should be a priority.
Here are a few of examples of road layouts around the highway connection which I have tried in some of my cities. The 'grid' solution on the left is horrible and jams quickly. The other two had a much longer life span before traffic problems began to make them unusable, although the curved road does take up more space!
I am going to suggest something perhaps slightly radical and possibly unacceptible here, which is that the best way to deal with large populations in SimCity is not to have them.
The game does encourage population growth (the first Sim World challenge was a population boom challenge). The City Hall requires 600,000 population to add all modules to win the Big Government Achievement, plus the Jumbo and Mega region Achievements require packing in a lot of Sims in each city unless you use one of the really big regions.
The fundamental problem, however, is that the game simply does not support large cities without extreme measures. A city that has managable traffic, which can provide sufficient services without bankruptcy, has enough space for specialization buildings and the infrastructure that supports them, a successful city that has room for all wealth levels, does NOT have ROOM for high populations!
As populations rise, it puts more pressure on city services, requiring higher level buildings with additional modules. Populations also fluctuate more as they expand, making it much harder to keep worker / shopper demand in balance. It also becomes more difficult to maintain the different wealth levels in balance, as higher wealth populations become more sensitive to city problems such as pollution or crime, which tend to worsen as the population increases. In short, the difficulty curve of the game increases exponentially as the city size increases.
Avenues are 48 meters wide, streets are 24 meters wide. Replacing the middle street with an avenue means both spaces lose 12 meters so they are now too small to fit a high density building which means these houses will never increase density
Specialization is designed to be the solution for the fact that the tax system doesn't work properly (see the Government: Treasury & Budget article). But specialization takes up valuable space; polluting mines and factories make your Sims sick and discourage higher wealth settlement. Casinos are cleaner, but are financially hit and miss, and the extra crime will drive away your rich citizens. The compromises the game requires in order to be successful, be it economically or in creating happiness and wealth, or maxing out a specialization HQ etc, tend to all run contrary to growing cities anything beyond a small town.
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In conclusion one guarenteed way to reduce traffic in cities with high populations is to reduce the population! I'm not suggesting mass sim-icide, but it's almost certain you can accomplish more with less.
Whatever you do I strongly recommend rather than losing your temper with traffic, try accepting that you're creating a small town, not a city and work with the space available!
Avenues are useful for moving around city traffic in larger volumes, but they are expensive and can be awkward to fit in later.
In general it is a great idea if you can decide where you want to put avenues and leave a gap so you can add them later on. Not doing this means either capping the density of nearby zoned buildings, or requiring a significant re-build which can be very expensive and time consuming.
This is explained somewhat more coherently in the Zoning & Density and Roads & Mass Transit: Upgrading & Zone Density articles.
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Ultimately the best layout tends to be one which is best suited to the individual city topography, specialization and there is no substitute for investing heavily in good road infrastructure! That said, it is always useful to have an understanding of the various merits and problems of particular pattern-based layouts when it comes to planning out your city. You may not want to apply them to your whole city, but seeing how they work (and don't work) in small areas can give you a starting point and showing where anticipate weak points and failures are likely to occur.
If money is no object then you can plan out great road network before your city even begins: "Town Highway Speed Build" - TOvlogs
The grid pattern is the cheapest and most efficient design for establishing a city, but it quickly fails as a traffic solution due to the 4-way intersections and poor regional connection, it also lacks a central focus point for high value and high attraction buildings.
One way to improve a grid pattern is the Cobblestone pattern. This is better than the standard grid because it reduces the number of 4-way intersections; you can also adapt an existing grid to this pattern easily. It is relatively cheap, but can be hard to upgrade existing roads.
Grid-type layouts do tend to work well in small local areas. If you can use mass transit to ship in workers effectively, then grids can work for industrial specialization areas where a limited number of service vehicles can travel up and down in an efficient way. Combine with a rail / sea link to keep traffic out of the rest of your city. It also works well for creating local communities within suburban areas as its easy to manage the balance between shops, jobs, homes, schools etc.
An alternative to the basic grid is to use a brick pattern which uses rectangular blocks with every other row offset. It can be a little fussy to build, but it has no wasted space and cuts 4-way intersections down to 3.
The principal weakness of this layout is that it can be complicated to upgrade, in fact if you don't plan for wider roads from the outset you could find you need to rebuild your whole city. It is also not very flexible for fitting in larger buildings. Like the grid it is also not easy to create areas of focus.
Overall, however, it is a useful pattern which can work well for small areas and it definitely lasts longer before traffic headaches set in than the basic grid.
Aside from the fact the game doesn't draw circles well, the positive aspect of reducing the number of intersections is offset by the fact that lots of space is lost.
The basic form of the circular city layout looks like a crosshair. I found that although the center is the obvious place to place high value city-center buildings, in practice the traffic build-up made it more practical to put those on the outside ring.
The crosshair layout can be improved by offsetting the intersections turning 4-way intersections into much less awful 3-way intersections.
Interlocking shapes such as hexagon or octagon patterns reduce the number of intersections, but unlike circular solutions they tend to waste less space whilst keeping traffic flowing as you can see in the example video link below.
One downside is that they can be difficult to actually draw and you can run into density related issues depending on the scale of your individual shapes. The complexity of drawing such a layout does make it more difficult than grids to fit in awkward size buildings and to keep specialization chains together.
It is, however, relatively cheap and a huge improvement on traffic flow verses a grid without the huge loss of space of circular based solutions.