What is the optimal grid size?

Someone Did The Math (Practical Engineering: The Optimal Square Grid by me22.ca) and I have summarised that content here - note that their numbers refer to the size of each square including roads, but I will use the sizes between the roads as this is more natural to most.

• The optimal square grid size with standard 2-lane roads is 10x10 which leads to a density of 66.666...%, even though it leaves a 2x2 "dead zone" in the middle. This is also cheapest in terms of road-building.

• The most obvious 8x8 grid is "only" 64% efficient, which may not sound much worse, but requires 50% more road length and is therefore that much more expensive than the previous option.

• For grids bounded by 4-lane roads, the optimal size is 12x12 but density drops to a meagre 50%.

• You can get higher density by using rectangular zones instead of grids - e.g. 8x14 is 70% density and 8x30 is 75% - but there are obvious disadvantages to this, notably in terms of traffic flow.

I use the 'Battery' Method for starting (Google YouTube Battery City Skylines). This provides a 4 x 8 grid, either side of a large one-way system.

Most importantly, turn off Traffic Lights ALWAYS. When Traffic lights went out in London, it was found that there were fewer snarl ups on the roads and traffic moved more smoothly - it's worth remembering that. The reason is that a red light will stop traffic, even when it's not impeded, whereas no traffic light will not.