A great case study for his traditional city movement is Tokyo. Most "suburban" areas are like his future 'traditional' city: 1 car width wide streets, walking-centric. All you need is exceptional public transportation - subway, rail. Drop yourself pretty much anywhere in Tokyo suburbs in Google Street View and you can see how a city of many multi-millions lives this way, no grids or arteries required.

The problem with doing this in Manhattan is that you have pretty hard boundaries for where the city should end, forcing development upwards.