180 degree rotational symmetry happens because almost all roads are bidirectional -- if there's a road pointing north, it's also a road pointing south.
90 degree symmetry seems like a consequence of the road system consisting more of straightness and 90 degree turns, with no other specific angle being common.
Rio fits the bill. There's no overarching grid, but if you zoom into any small area, you'll usually find a pattern of rectangular blocks with 90 degree intersections.
As far as I can see, the only viable way out rotational symmetry would be to use concentric 'ring-blocks' either for local areas or for the city as a whole. The rings would cancel themselves out, and the 'spokes' could be places relatively freely.
So... Canberra might have an interesting distribution?
90 degree symmetry seems like a consequence of the road system consisting more of straightness and 90 degree turns, with no other specific angle being common.
https://www.google.com/maps/@-22.9111837,-43.2566471,14z
Rio fits the bill. There's no overarching grid, but if you zoom into any small area, you'll usually find a pattern of rectangular blocks with 90 degree intersections.
As far as I can see, the only viable way out rotational symmetry would be to use concentric 'ring-blocks' either for local areas or for the city as a whole. The rings would cancel themselves out, and the 'spokes' could be places relatively freely.
So... Canberra might have an interesting distribution?
https://www.google.com/maps/place/Canberra+ACT+2601/@-35.288...