Oasys has developed the worlds most advance crowd simulator, MassMotion. It is able to simulate, analyse and visualise how people will move through a spaces. This is definitely a helpful tool for architects and city planners as it would help foresee any problems such as bottle necks and high traffic areas that would hinder the smooth flow of people through spaces. I also find the high quality 3d rendered visualisation to be quite a good addition, as this would allow persons that may not necessarily know what they are looking at to get a visual sense of the information. Follow the link to the source for more information.