Its too bad there is only one lane of traffic in the simulators. There are interesting insights to be had when simulating multiple lanes and adding "incentive" lanes. One of the first Java applets was a multi-lane simulator which showed the impact of people getting on to a 4 lane freeway, merging all the way across to the HOV lane on the left, then merging all the way across again to get off. Versus having the HOV lane on the right, vs having no HOV lanes.

The fun stuff is that queuing theory applies to all sorts of things like packets and getting seats on an airline. Lots of fun to play with.