Late edit: It turns out that this has big noise problems because the ramps generate highway-level noise. Converting them to streets helps for noise, but it kills the speed benefit of the tile. Oh well, sorry folks
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All right GAF, I think I've cracked the code and found the ultimate tile system.
I present to you: OctoMesh
(
higher res)
OctoMesh Junior (on the left):
http://steamcommunity.com/sharedfiles/filedetails/?id=413572398
Starter version with one-way streets instead of ramps. Can upgrade those to ramps later.
OctoMesh Gold (on the right):
http://steamcommunity.com/sharedfiles/filedetails/?id=413573112
Version with ramps.
This thing allows travelling at highway speeds horizontally and vertically (green) and on the centre "roundabout" (red) thanks to the ramps. There are connections all over the place for wherever people want to go and it has lots of building space. The gold version has one block which is all ramps - if you want to put something there, just convert one of the ramps back to a one-way street. For really big buildings, you can bulldoze the two-way roads at the centre of the octagon and it doesn't slow things down much. The ones not highlighted on the right are all two-way streets for flexibility, and then the ramps are there as the alternate route for speed.
Well, that's the concept anyway. Now to see how much traffic it can really handle. There's no way this would work in real life due to all the collisions, heh.
Surprisingly, you can arbitrarily rotate the tiles in your pattern and it still works thanks to the rotational symmetry of the road directions and connections. Handy if you have a really tall+narrow or wide+flat building you'd like to place a certain way. You can also fill up the centre octagon with whatever streets you like since it's not the main path for speed. I just left it blank for zoning as the default.
Edit: Added a version with elevated connectors. This should improve speed on the fast lanes and make things a lot easier for random connections using the upper level.
Starter:
http://steamcommunity.com/sharedfiles/filedetails/?id=413591651
Ramps:
http://steamcommunity.com/sharedfiles/filedetails/?id=413591710