Paul Torrens, a geographer at the University of Arkansas, posted some visuals of a geosimulation he's put together modeling urban crowd behavior in response to a car fire/explosion. His site's been swamped with hits since the thing was mentioned on a few blogs and the word spread. Take a look at the video, which is limited but suggests some interesting possibilities for computer sims for urban warfare. He's got some other groovy sims on the site, too, worth looking at.

You can find the crowd simulator at http://www.geosimulation.org/crowds/