a column (i.e. a non-traversable obstacle) is placed in front of the exit. The authors of [@HePED; @panic], who studied the same situation and found surprising results, called for complementary data from experiments or other models to confirm their findings. We therefore study the scenarios of [@HePED; @panic] in the following.

Fig. \[plot\_15\] shows a mid time stage of evacuations for a column placed central in front of the exit. The size of the column is $3\times 3$ cells. It is placed within a distance of one cell from the door.

![Mid time configuration of an evacuation of a room with one door at the middle of the top wall with an additional column of size $3\times 3$ cells placed in front of it. The width of the door is one cell.[]{data-label="plot_15"}](\DIR/fig25.ps){width="0.5\columnwidth"}

We compare with situations where this column has been shifted (to the left or right) parallel to the exit by one or two lattice sites. Our focus is on the ordered regime where friction effects are strongest. The static floor fields $S$ used in the simulations have been calculated using a Manhattan metric (for details see [@aki]). Fig. \[plot\_16\] shows the averaged evacuation times as a function of 