The blue and green streets are one-way streets in the direction indicated. The red and orange are two-way streets, with a wrinkle--on the orange roads, the you drive on the left, rather than on the right (with a visual barrier between, to prevent confusing drivers).
The result of this complicated pattern is that every single turn you make on the network is a 'safe' turning movement that does not require crossing traffic, so there is no-need for stop-signs or traffic lights, only terminating turn-pockets onto and off of roads. Consequently, you can go pretty much as fast as you like.
The turning rule is: You never cross traffic. So you can go left from green onto yellow, and from blue onto yellow. The rule ought to have been 'rights onto red, lefts onto yellow'.
Travel in the NW-->SE direction(blue, green paths) is fast direct. But travel in the NE-->SW is a pain (gray path), because every other road you have to take a 'red' street, and wind up going about 50% more distance. I think the lack of streetlights would be worth it, but not sure. The plan would be most suitable for a city where most of the travel is in one direction, such as a mountain valley.
I can't see retrofitting an existing city, but it would make a novel subdivision plat, or the traffic plan for a tabula rasa city like Brasilia or Masdar.
For local streets, connecting these main-streets, you can do pretty much what you want, with some limited exceptions: The turn pockets have to be oriented toward the direction of flow, so as not to generate temptation to 'cross' in front of traffic, on red or yellow streets:
- I don't propose to make this real in the least--it's a bad idea in a multitude of ways. It's a traffic network for SimCity, or for Traffic Simulation software. If you are working with a 'omnipotent' traffic allocator, which knows the whole network (and never gets lost) it just chooses the most direct route for each residential cell and the nearest employment cell.
A system like this would drive most people nuts. They would have to constantly be aware of where they are because if they miss a turn, its much more costly, timewise, to correct it than on a square grid.Most places don't actually HAVE grids, or ones of analogous scale. Grids are more the exception than the rule, actually. Phoenix has one due to it's near-total lack of geography (rivers, mountains, valleys, etc).