Infrastructure seems to have some role to play in the success of cities (a less macro version of guns, germs and steel), and so I wonder if a grid pattern close to an ideal for city streets? After returning to New York and seeing how traffic generally moves, even when the streets are apparently full, I wonder if the combination of multiple paths moving in the same direction with smallish streets and smallish blocks is actually quite efficient where there is no pricing or limited access.
A grid would be somewhat self-balancing (as a street backs up, traffic naturally diverts to parallel streets if there are "block-the-box" rules, have some redundancy (with no absolute bottlenecks, no one point locks up the system or cuts off an area), and deliver some information (although not information rich, a quick glance at a street suggests is somewhat predictive of local and even less local traffic - in part because of the self-balancing aspects).
And this is most interesting as it isn't clear that the road designers were worried about traffic.
