Besides the obvious practical relevance, pedestrian and crowd
dynamics provide fascinating examples for collective phenomena
and complex behaviour. Thus it is not surprising that a variety
of physics-based approaches have successfully been applied in
recent years.

In the talk four main aspects will be addressed:

1. Surprisingly, the empirical situation is far from clear. There is
   still no consensus about some of the most fundamental properties of
   pedestrian dynamics. This is reflected in very different legal
   regulations even within different parts of Germany.

2. The general belief about the events during an emergency situation
   is entirely wrong! Individuals behave very differently from
   what is usually reported in mass media. Notions like "panic" have
   not played any role in almost all known catastrophic events.

3. An overview of modelling approaches is given. Pedestrian crowds can
   either be viewed as exotic fluids, particles which interact via (social)
   forces violating Newton's laws or stochastic systems. We focus on a
   cellular automata approach proposed by us which by now has become the
   standard simulation tool.

4. Finally, as an application, the development of a so-called
   "evacuation assistent" for the Espritarena Düsseldorf is described.
   It uses fast online simulations based on a cellular automaton model
   which allow to react quickly to a specific emergency situation and
   support local authorities in their decision making.