The main difference I see is that most of Europe isn't built on grids. It strikes me they cause as many problems as they solve. Most road networks are essenti

The main difference I see is that most of Europe isn't built on grids. It strikes me they cause as many problems as they solve. Most road networks are essentially hierarchical - you have (more or less) arteries, collectors/feeders, and local roads. Local roads should be for local access, and collectors/feeders consolidate access between arteries and local roads. In the grid, it feels like there is no local road - just arteries (eg Barcelona's diagonals) and .. roads. You can try to downgrade a feeder into a local road using "traffic calming" measures; speed bumps, speed limits, one way systems - but the moment there's any congestion on the intended feeders, people will try to route around it and bring the congestion to the unintended feeders. The whole "superblock" concept appears simply to reintroduce local roads into a system that was built without them - which isn't actually an issue typical of most European cities.