I can get my cities to around 450,000 people before traffic becomes too much, unmanagable.
But how do I get to 450,000 in the first place? Hi ways every where, on and off ramps every where, unrealistic and ugly, but once I hit 500k even that solution dies under the weight of traffic.
It would be good if say installing the Space Elevator trippled the amount of goods lorries and commercial vehicles can carry, whilst say setting 75% of office workers and 25% of industry workers into "work from home" types. Not an elegant solution, but would allow me to push on through the 500k max I now have.