CA Approach to Collective Phenomena in Pedestrian Dynamics - Cellular Automata - page 240

(e.g. following people walking some distance ahead) into a local interaction (with
the “trace”). This allows for a much more e cient simulation on a computer.
Many interesting collective effects and self-organization phenomena have
been observed in pedestrian dynamics (for a review, see [2,3,17]):
Jamming : At large densities various kinds of jamming phenomena occur,
e.g. when many people try to leave a large room at the same time. This clogging
effect is typical for a bottleneck situation where the flow is limited by a door
or narrowing and is important for practical applications, especially evacuation
simulations. Other types of jamming occur in the case of counterflow where two
groups of pedestrians mutually block each other.
Lane formation : In counterflow, i.e. two groups of people moving in oppo-
site directions, a kind of spontaneous symmetry breaking occurs (see Sec. 3.1).
The motion of the pedestrians can self-organize in such a way that (dynamically
varying) lanes are formed where people move in just one direction [4]. In this
way, strong interactions with oncoming pedestrians are reduced and a higher
walking speed is possible.
Fig. 1. Illustration of lane formation in counterflow in a narrow corridor.
Oscillations : In counterflow at bottlenecks, e.g. doors, one can observe os-
cillatory changes of the direction of motion (see Fig. 2). Once a pedestrian is
able to pass the bottleneck it becomes easier for others to follow in the same
direction until somebody is able to pass the bottleneck in the opposite direction.
Fig. 2. Illustration of flow oscillations at a door with counterflow.