  Analogies between the dynamics of pedestrian crowds and granular media have
long been hinted at.They seem all the more promising as the crowd is (very)
dense, in which case the mechanical constraints prohibiting overlapsmight
prevail over the decisional component of pedestrian dynamics. These analogies
and their origins are probed in two distinct settings, (i) a flow through a
narrow bottleneck and (ii) crossing of a static assembly by an intruder.
Several quantitative similarities have been reported for the former setting and
are discussed here, while setting (ii) reveals discrepancies in the response
pattern, which areascribed to the pedestrians' ability to perceive, anticipate
and self-propel.
