Sim City 5 is what the Sim City team calls a "complete simulation". This means that every single sim (and supplies, garbage, etc) in a city is simulated. Sims run around, do errands, go to school, and go to work. Their goal is to earn money and exchange it for happiness.

The move to complete simulation also changed the core mechanic of Sim City. While land use management still plays an important role, designing an efficient transportation system is the most important aspect of designing a successful city. In the simplest terms, sims need to travel to be happy and your city needs happy sims to grow.

I was immediately sucked in. 10 hours would go by before I realized that I had skipped meals and the sun had gone down. Sometimes I would try to pull myself away to go pee and end up half standing, half sitting in front of my computer for 45 minutes tweaking "just one more thing."

I built a few cities. Each one I managed to grow larger than the previous. 100k citizens, 200k, 500k. But each time I built a new city I would hit the same wall. Citizens would complain of health problems and spend most of their days stuck in traffic. Some sims wouldn't get home from work until 6am the next day! This meant they couldn't bring home the happiness they had purchased and my city wouldn't grow.

So I went to the global leaderboards to see how the top players had solved this problem. What I discovered was truly disheartening. The top players were all hitting the same wall I was hitting, though they had managed to squeeze a couple 100k more sims into their cities first.

At this point the problem became obvious to me: the core mechanic of the game is designing an efficient transportation system, but the tools to build an efficient transportation system did not exist. There are very few alternatives to building more road capacity. What options do exist (street cars, busses, ferries) only raise population cap rather than eliminating the transportation bottleneck.

And then I realized that Sim City 5 isn't broken. It copies the American approach to transportation systems, which is broken. Simple tools like bike lanes, narrow lane widths for cars, and pedestrian zones can have big positive impacts on transportation efficiency and public health. Both Sim City and American urban planning almost completely overlook these tried and true solutions.