Cities: Skylines – Optimised 6-Lane-Road Gridded City Layout

This is the most efficient layout that I’ve found for achieving sustainable, scalable, high-population cities.
There is a cap on the number of road cells that you are allowed to place, some x^2 number. Fuck! This is definitely the bottleneck on city magnitude: No roads.. no houses, no buildings; you have to make every placed road cell count.
That means that to make the most of your roads, they need to not overlap their build zone where at all possible – you need to avoid 90 degree angles with roads; to just have lots of straight roads with 4 lanes of housing/commerce/industry on either side. You can’t get away with long streets of only 2-lane roads, as the traffic builds up and grinds your city to a complete halt with even short streets. To deal with this, and to make your road cells as efficient as possible, they need to be the two-way 6-lane roads. One-way roads could have a role to play. It also helps for your city to be as large as possible, as it spreads the now-capped traffic among a larger area.
So those are the basis for your city grid. To use them well, you need to use them to lay repeating optimised pre-designed cells – a layout that optimally considers for the long reach needed to achieve coverage of services. I think I’ve found an extremely efficient layout for these units. All I might really need to do is tinker with service building placement slightly for maximum optimisation. This layout on the whole is definitely a winner though.
A great perk of this highly efficient, dense grid is that designing efficient transport is simplified and extremely easy to scale.
I’m using metro for ALL of my transport, to keep the commuters off of the roads (not in their cars), and to keep the infrastructure off of ground level to free up space. The stations are evenly spread for efficient, even coverage, and then they are chained together at the edges of the map for easy switching. The least efficient journey around my city using this system is √2 of the distance, which is still MUCH faster than walking/cars/buses. The maximum amount of walking a citizen needs to do to get from any one place in the city to any other using metro stops is extremely low. My transport expenses are actually exceeded by the ticket income, and the metro trains are almost always packed full. EXTREMELY efficient.