I've been messing around with mods, and I find myself having a lot of fun with this game again. Here are a few shots from a concept city I had in mind.
The concept: Pack over 700,000 sims into the city, have no mass transit, and keep traffic manageable.
Result: Pretty easy with a few choice mods. One way roads, and highways really help out in this regard. I can add all sorts of outlets for traffic so that the main roads don't get too congested. The regional roads mod helps out a ton too, since I can utilize the space outside of the city box for my road network, and leave more space inside the box for actual buildings.
Here is a bottom section of the city. The basic "neighborhood unit" is one giant one way street loop. It goes from the top of the pic to the bottom. the community college eats up the students, and the workers have lots of space to go to the factories. I've highlighted the tunnel where the road loops around and goes all the way back so that the sims can go home. You can also see the additional elevated highway that I have looping all around the city. It adds yet another path for sims to drive, which eases congestion.
This is the top section, so you can see the residential buildings that the sims came from. You can see each loop feeding back into itself. There are also onramps and offramps that connect each loop to each other seamlessly. Since ramps don't have traffic lights, traffic flows very smoothly between them.
Here is the bottom part of the city again where you can see more of the regional roads that I've put in that adds inlets and outlets from the main regional road. No longer am I bottlenecked by that tiny ass city entrance. I can add more entrances wherever I like.
For funsies, I also added casinos and landmarks to a section of the freeway, which adds even more cars. My layout can handle it with no problem, whereas in vanilla SimCity, this would probably kill your roads.
Everyone gets to work and school on time and then back home. During nighttime, the roads are clear since everyone made it back home very quickly.
That was a nice ride, Maxis. Decades of fun with the Sims and SimCity but you are going to achieve an extraordinary exploit of destroying both of your cash cows within 18 months. Bravo