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Openttd is a great logistics simulator, but it's not really a traffic simulator. Traffic by it's nature requires a lot of independent agents deciding how to use a shared resource, and the resulting conflicts, like Braess' paradox[0]. As far as I've seen, the only game that does well at this is Cities Skylines. OpenTTD on the other hand is my favorite part of factorio.

[0]: https://en.wikipedia.org/wiki/Braess%27s_paradox?wprov=sfla1



I've personally found it pretty easy to get around. In particular, just build long stretches of roads without any intersections. Just "s-curve" like a snake, especially around industrial centers (all traffic originates in industry, and don't seem to "return" to industry in Cities Skylines).

Maximize the distance of these singular roads, and build out your road system like a computer-science definition of a tree. Its not very realistic, but it solves more or less all the issues of Cities Skylines. (Or perhaps it is realistic, and matches the behavior of neighborhood planners in the real world).

In contrast, OpenTTD encourages hub/spoke model and recycling of centers. I think its sizes are off but the overall gameplay loop is correct here.

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OpenTTD's "traffic" is pretty dumb, but its infinite. As long as you've got high station ratings, the station will expand and traffic will increase. It doesn't matter what design you have, the traffic increases until you can no longer support it.

So OpenTTD is somewhat self balancing. The stronger a player you are, the more traffic you generate. The weaker a player you are, the less traffic you generate.


> all traffic originates in industry, and don't seem to "return" to industry in Cities Skylines

It absolutely does come back? I've had major traffic headaches from returning trucks. If I don't build rail for trucks, my cities are usually screwed over by that.

> Maximize the distance of these singular roads, and build out your road system like a computer-science definition of a tree. Its not very realistic, but it solves more or less all the issues of Cities Skylines. (Or perhaps it is realistic, and matches the behavior of neighborhood planners in the real world).

Trees create massive chokepoints when traveling within the city, so I don't think its likely to work in a large city (though if you squint, road hierarchy is somewhat tree-like, I suppose, though with more intra-branch connections). I suspect you simply haven't gotten cities big enough to actually have traffic, especially if you think most traffic is trucks. It does take a bit for personal car traffic to be heavy enough to be a problem.

The unique thing about car traffic vs station demand is that the overall speed depends on the quantity of cars on the road, with maximal throughput occurring before a fully occupied road. That's how you get weird effects like Braess paradox.

OpenTTD is much better at simulating public transit systems, Cities Skylines is better at simulating traffic.


> It absolutely does come back? I've had major traffic headaches from returning trucks. If I don't build rail for trucks, my cities are usually screwed over by that.

Don't the trucks go into the Cargo station, and then disappear?

In OpenTTD, if you have a truck -> rail station, the truck drops items off, then have to return to Coal/Forests/whatever to pick up items again.

In Cities: Skylines, the truck hops onto the train, and then vanishes. Its been a while since I've played Skylines, maybe I'm mis-remembering?

> Trees create massive chokepoints when traveling within the city, so I don't think its likely to work in a large city (though if you squint, road hierarchy is somewhat tree-like, I suppose, though with more intra-branch connections). I suspect you simply haven't gotten cities big enough to actually have traffic, especially if you think most traffic is trucks. It does take a bit for personal car traffic to be heavy enough to be a problem.

Or maybe I'm just abusing the behavior of cargo stations too much.

The cargo-station "teleports" traffic somewhere else, and seems to magically erase return traffic. Use / abuse of cargo-stations seems key in making cities grow larger.

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EDIT: Ah, I misremembered. Seems like the return traffic does need to be accounted for. In any case, the industry -> Cargo Train terminal is really all you need to design against. With a proper industry block (or S-road / snake-like road), all industry goes to cargo train, and all of them return to industry, with no intersections potentially wrecking them.


> (though if you squint, road hierarchy is somewhat tree-like, I suppose, though with more intra-branch connections)

Intra-branch connections are your mistake. Don't do that. If you're purely a tree-shape, there's no Braess paradox because each neighborhood (or housing unit) only has _one_ path to the rest of the city.

The minute you have 2, 3, or 4 different paths to reach the same house, is the minute that paradox starts to bite you in the ass. So just avoid it completely with a 100% tree-like branching behavior. One path means you have absolute control and force the little cars to go down the exact paths you want.

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Yes, roads and intersections will saturate. At that point, stop building in that neighborhood and build another branch of your tree.

I don't think I ever found a reason to do a non-tree design in the game, aside from simulating realism. But if you're just designing neighborhoods to minimize traffic and maximize population, a pure tree is the obvious approach.

IIRC, there's no residential-to-residential traffic. Its all residential-to-commercial, and then commercial-to-residential. That's why a pure tree works. Or industry-to-commercial, and then commercial-to-industry.




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