these two regimes an [*cooperative regime*]{} [^2] exists where the combination of interactions with the static and the dynamic floor fields minimizes the evacuation time. Fig. \[phases\] shows a schematical phase diagram in the space of the couplings $k_S$ and $k_D$.

![Schematic phase diagram.[]{data-label="phases"}](\DIR/fig3.eps){width="0.85\columnwidth"}

Here we want to focus on the influence of the friction parameter $\mu$ on the evacuation times in the three main regimes. As we will see the influence of $\mu$ is strongest in the ordered regime. This will lead to a new interpretation of this regime.

We consider a grid of size $63\times 63$ sites with a small exit of one cell in the middle of one wall. The particles are initially distributed randomly and try to leave the room. The only information they get is through the floor fields. The strength of the static floor field at a site $(i,j)$ is inversely proportional to the distance of $(i,j)$ from the exit measured using the metric described in [@aki0]. Fig. \[snap\] shows a typical stage of the dynamics for an initial particle density of $\rho=0.3$, i.e. 1116 particles. A typical half-circle jamming configuration in front of the door develops.

![Typical middle stage of the dynamics of 