The professional simulators are prohibitively expensive for individuals to play around with, sadly. I had the chance to try VISSIM recently, and the UI was overwhelming -- the general public would never casually learn to use something that intricate. I'm trying to strike a balance between the heavy-duty simulation packages and existing city sim games -- something with a good approximation of a real city by default, and something that's very easy for anybody to pick up.

Agreed - I used VISSIM for some work in a university transportation research lab, and it was very interesting after learning how to use it - but both expensive and very intricate to learn. It even supports other types of transportation, like rail networks. It would be great to have a simplified version or some kind of middle ground to help people understand these complex systems.

Agreed, I was mainly answering the point about tools city planners use to model traffic ahead of time.

I've worked with transport and traffic modellers for years now and still don't understand the software packages very well.