
Left: a 2011 crowd dynamics depiction showing a large auditorium cleared calmly through a small exist. In other scenerios, according to American NSF researcher Paul Torrens, “from an initial start point of rest, agents begin to evacuate a large auditorium quickly by running as fast as possible to safety through a narrow exit. Wedge-like bottlenecks soon form at the mouth of the exit corridor and congestion begins to ripple back through the crowd, impeding further clearing. Similar dynamics are often observed during rush hour commutes on highways.” [5] Right: Andreas Schadschneider's 2010 video (Ѻ)from above opposite flow dynamics studies.

Left: a 2011 crowd dynamics depiction showing a large auditorium cleared calmly through a small exist. In other scenerios, according to American NSF researcher Paul Torrens, “from an initial start point of rest, agents begin to evacuate a large auditorium quickly by running as fast as possible to safety through a narrow exit. Wedge-like bottlenecks soon form at the mouth of the exit corridor and congestion begins to ripple back through the crowd, impeding further clearing. Similar dynamics are often observed during rush hour commutes on highways.” [5] Right: Andreas Schadschneider's 2010 video (Ѻ)from above opposite flow dynamics studies.

In human physics, crowd dynamics is the study of "crowd behaviors" in particular abnormal crowd behavior such as people's reactions and movement patterns in emergencies, such as fire, or in heightened festivity situations such as when critical density levels (four people per square meter) are reached; often times, theories involved computation models in which people are modeled as particles (human particles) or fluids (human fluids) and crowds are studied in masse.

History
In 1895, Gustave le Bon, in his The Crowd, outlined some early physics-like ideas on how people in crowds are in a special magnetized like state.

The science of crowd dynamics seems to have been around since at least the 1950s.

The fluid mechanics or gas system models of crowd dynamics was first introduced in 1971 by Australian mechanical engineer Roy Henderson.

In 1995, Dirk Helbing, in his Quantitative Sociodynamics, outlines a social force model, according to which the motion of pedestrians can be ascribed to a combination of a driving force, that reflects the person’s internal motivation to move in a given direction at a certain speed, and repulsive forces describing the effects of interactions with other pedestrians and boundaries such as walls or obstacles in streets.

Scottish mathematician Keith Still, who did his 2000 PhD dissertation on “Crowd Dynamics”, is sometimes slated as the world's leading expert on crowd dynamics. [1]

Recent models by S. Hoogendoorn (2004), W.J. Yu (2005), and B. Steffen (2008), have used Newtonian force models. [3]

In 2010, German physicist Andreas Schadschneider was working on a project to develop an "evacuation assistant", still of video (V) from above study, shown (above), aimed to make the evacuation of large buildings safer; using pedestrian dynamics theories borrow ideas from physics to model people as particles. [4] Schadschneider recorded various interaction scenarios of people from above as opposite flows interject in close-paced hallways and as people leave stadiums. [2]

References
1. Still, G. Keith. (2000). “Crowd Dynamics” (abstract), PhD dissertation, University of Warwick, Department of Mathematics.
2. Edwards, Lin. (2010). “Crowd Dynamics in the Spotlight after Duisburg Disaster” (two videos), Phys.org, Jul 29.
3. Moussaid, Mehdi. (2011). “The Collective Dynamics of Human Crowd Motion: Where Physics Meets Cognitive Science” (summary), PhD thesis, University of Toulouse, Jan 14.
4. Staff. (2010). “I’m a Football Fan … Get me Out of Here” (abs), Physics World, Jul 1.
5. Torrens, Paul M. (2011). “A Crowded World”, National Science Foundation.