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During research for this project I had a look around the rest of the OGF world at existing settlements and countries. There are many examples of great work by dedicated users. However, there are also many examples of otherwise well-designed projects that are let down by their transport network design and layout - in particular roads.
Others have written good content about this before so I won't repeat everything, but I do feel that I can add to this existing information by focusing specifically on roads.
This has motivated me to write a summary of my recommendations and tips on the subject. I hope that this post can serve as a guide to help people develop networks of roads, streets and highways that reflect a more realistic depiction of the 'real world'.
Who do you think you are??
Before beginning I feel that I should briefly explain my background. In my day job, I work to understand, fix and improve cities. Dealing with transport networks and systems is a large part of my daily work and ongoing projects.
This may or may not make it more likely that you will heed my advice, but just putting it out there for now!
Consider the overarching vision of OGF - 'Verisimilitude' (like real). The recommended way to achieve this is to look at existing 'real world' settlements and study their layouts. There is an excellent guide on this subject which may be found here.
The same principles should be applied to road networks.
In particular, it is vital that your transport networks are in line with the 'model city' that you choose to use as your template. These are the blood vessels, veins and capillaries of cities and towns. Without them, human settlements cannot function. And like real-life circulatory systems, no two are exactly the same.
For example, if you are basing your OGF mapping on Oklahoma City in the United States, it will probably involve lots of 90 degree angles, grids and wide motorways.
On the other hand, if you are using Sydney, Australia as your model city, it will probably involve lots of curved thoroughfares, narrow streets and few free-flowing motorways.
If you mismatch your road network to your city's urban form, it will not make sense.
To avoid the problem, you must determine the style of your road network before you begin drawing anything. Work this out using your model city and add your own unique flairs, consistent with your country and city's lore.
Once you have the broad principles worked out, you can start drawing!
My first tip for doing this is to start mapping from where your settlement was first established. This is likely to be in or near your city centre. Start by drawing out this area in at least some detail (i.e. not just primary and secondary roads).
Again, the form of the road network will depend on the principles that you have hopefully already determined from the previous section. Options include a dense grid of small laneways and streets in the inner suburbs (example), or an immediate transition into suburbia with wide boulevards and meandering residential streets (example).
These first few tasks will give you a taste for what the rest of your city will be like. To borrow from Lenin - "everything is connected to everything else". In other words, what you set down in this initial phase will strongly influence what the rest of the road network looks like.
My second tip is to plan for other transport modes when you lay down your first roads (e.g. railways, tram lines, bike paths). These tend to be at their most dense in urban cores so make sure that you leave enough room!
Expansion and details
Once you have a solid base to work from in your city centre, I would recommend picking a general direction and working outwards from there. Don't try to build towards all compass bearings simultaneously - you will quickly be overwhelmed. The number of considerations to think about over such a large area at once is not conducive to good road network design.
Continue doing this for a while - then you can go back and start working on the other directions from the city centre.
If you are planning a polycentric city (i.e. one with multiple centres/hubs), then it would be useful to repeat the exercise above for each hub. In time, this will create 'hub and spoke' road networks that centre on each one - a realistic depiction of this type of urban form.
If you are planning a city that has grown over time and was founded before the 1910s/1920s, consider that areas built before the widespread use of cars are very different to those designed afterwards. For pre-car areas, streets will be closer together, there will be (or will have been) much more public transport available, and there will be (or will have been) more small shops rather than fewer large shopping centres. In other works, these neighbourhoods will be better for walking, cycling and taking public transport. So make sure that you build these characteristics into the network as either a nod to a past that has since been erased by car-centric planning or as an old street network that still exists.
Intracity connections and rural areas
These two types of areas deserve special attention as they require different thinking to urban contexts.
Don't just draw straight lines between your towns and cities. Think about the physical geography of the country. Place some rivers, creeks, mountain peaks or other features before you start drawing your roads to help you. Again, have a look at some real-life examples of intra-city transport connections in similar topography.
I won't dwell for too long on this topic as this can vary significantly depending on the model country chosen. Just remember that rural areas will not require nearly as high a density of major roads as urban areas. Roads also tend to meet in towns or other settlements, as these will have usually developed at road junctions because of the economic activity that this brings.
I have covered a few of the most common mistakes in the sections above. A few more specific entries are outlined below.
This has been written about before and there are tools available to help. However, this problem is worth repeating here as a reminder to take particular care with roads.
Think about design features like turning radii - the higher the intended speed limit, the longer the curves will need to be. A local residential street does not need huge amounts of room for vehicles to get around a corner at 100km/h. This is far from the only consideration, but just be careful not to build roads at too large or too small a scale.
Too many high-capacity roads
This is probably the most common one that I have seen in OGF and other geofictional cartography.
Basically, no city requires major eight-lane trunk roads every one kilometre or so. The volume of traffic required to meet the demand for this kind infrastructure in such a small area would be astronomical and is not replicated in 'real life' to my knowledge. Unless you are building some kind of planned ghost town like Naypyidaw, cut down on the use of high-capacity major roads in your city. Once again, look at your model city. Use a measuring tool in Google Earth or QGIS to look at the mean distance between a couple of main roads in urban areas and use this as a rule of thumb for that context. No need to over-engineer the network to the point where it looks a little ridiculous.
Non-car-based transport ignored
Regardless of how car-dependent your city is planned, there will always be a need for non-car based transport. This includes public transport, walking and cycling.
The extent and quality of the infrastructure is obviously up to you. However, it cannot be ignored entirely.
I see many cities and countries in OGF that only have roads or, more commonly, build the roads first and then try to squeeze in railways, bus routes and footpaths at some later stage. I would strongly recommend building your most important transport modes at the same time. This has a much better chance of having a network that makes sense by avoiding duplication, creating logical connections and making it look plausible.
Of course, this doesn't mean that your network has to be perfect. In fact, it is probably more realistic to have unfinished highways, train lines that don't connect properly and bike lanes that suddenly end into a six-lane trunk road. What this does mean is that regardless of whether your city is a multi-modal transport heaven like Rotterdam or a monument to the dominance of cars like Los Angeles, you will have to consider things that are not roads at some point. My recommendation would be to do this alongside your road network mapping rather than doing it later or ignoring it entirely. This makes it a more realistic map.
Topographical monotony or inconsistency
I have already touched on this in previous sections. All that I am recommending here is to avoid long stretches of straight lines everywhere directly connecting key features.
Unless your country is based on Kansas, it is extremely unlikely that the topography is totally flat. Think of where there might be some hills, mountain ranges, rivers or other obstacles for your road network to overcome. Add in some bridges, tunnels and curves, at least in some places. Otherwise it just looks like somebody has come along with a ruler and protractor to join everything together like some visual geometric puzzle.
I hope that this has been useful for at least some people. In the future, I might write up a few more of these to help people map better transport networks and build a better OGF world.
If anyone has any specific requests for topics, I'm happy to consider them. Until then, I'm also happy to answer any questions or take any suggestions/comments.
Define the principles of your road network. What is the history of your city? What does your model city look like? What its the key characteristics? Use this to map everything.
Start drawing your roads from where your settlement was founded. This makes it much easier to make the network feel organic and sets the scene for the rest of the city.
Create interesting topography. The extent and type will be up to you, but try not to just connect everything with straight lines everywhere!
Build your public transport, walking and cycling networks at the same time as your road network.
Don't build masses of motorways and other high-capacity roads. Think carefully about how much road capacity your city really needs. Look at your model city to get an idea.