> As explained in the video, above a certain crowd density, people physically lose the ability to control their movement in the mass of bodies and involuntarily

> As explained in the video, above a certain crowd density, people physically lose the ability to control their movement in the mass of bodies and involuntarily behave more like molecules in a fluid and less like individual actors. The people at the interface of that phase change have the choice to move backwards, but still press forwards even though it puts them into physical contact with other people. They can be partially excused for not knowing of the situation ahead of them, but they're still (usually, except in cases of fire/etc) making a free choice to physically touch and press themselves into and against other people. I am talking about people at the interface, not in the middle of it. If everybody in the crowd refused to voluntarily press somebody else, then no forces would be transmitted through the crowd. But pressing other people, particularly to jostle your way past them, is the nature of crowd psychology. For this reason people should avoid crowds entirely. Being in such a high density crowd is usually a choice.