Can anybody explain (or provide some resources that might do so) how the SimCity games, particularly Classic and 2000, calculate the interactions between different zones, and the influence of transportation infrastructure? I have an idea in mind, but much of it is closely modeled on the approach used in Sierra sims like Caesar and Pharaoh. Instead of sending entities along the roads a background scan would be performed at particular intervals that would operate in a similar manner. Another aspect involves a zone influence layer wherein each developed zone would contribute gradating and cumulative values to its surrounding tiles. These then need to be somehow pumped through the roads and other transit to influence the rest of the city. This is where the Sierra part comes in at the moment What I have in mind would likely be more dynamic than SimCity, but it would be a great help to understand how Maxis did things.

AFAIK SimCity's internals mostly run on cellular automata / anti-objects.

A good way to find out what effects different zones/structures/networks have would be to read the SimCity 4 walkthrough written by "thy451" -- people have basically reverse engineered the game's rules in that document through countless experiments =D

Well, for starters, the source for SimCity Clasic is openly available:
here.

Thanks, these are some very tasty resources and should provide me with some good hints as to how to proceed.

Anti-objects are a particularly fascinating subject. I'd actually been considering ways of using such an approach, but didn't have a word for it.

Remember that you aren't "simulating a city"... you are simulating information and relationships. Determine what information and what relationships and how those interconnect and you will be well on your way to simulating what it is that you want to represent in your game.