increases only for large friction parameters $\mu>\frac{1}{2}$.

The behaviour is different in the high density regime $\rho=0.3$ (fig. \[plot\_1b\]). One finds a weak increase of the evacuation time in the disordered and cooperative regime for high $\mu$ values ($\mu > 0.6$). Even if the particles are not packed close together in front of the door, they form a cue and hinder each other. Increasing $\mu$ leads to a sharp increase of the evacuation time in the ordered regime which first becomes larger than that in the cooperative regime and finally exceeds even that in the disordered regime. In fact it diverges for $\mu\longrightarrow 1$. This behaviour can be understood from the microscopic configurations occuring. A short time after the start of the evacuation nearly all particles of the system are forming a big jam in front of the door. In this large density region many conflicts occur and for large values of $\mu$ the outflow is strongly surpressed. Here the pressure between the pedestrians becomes so strong that any motion is almost impossible. Such a behaviour has been observed in panic situations and also in simulations using the social-force model [@panic]. It will be discussed in more detail in Sec. 