  We study the dynamics of pedestrian evacuations through a narrow doorway by
means of controlled experiments. The influence of the pedestrians' behaviours
is investigated by prescribing a selfish attitude to a fraction c\_s of the
participants, while the others behave politely. Thanks to an original setup
enabling the re-injection of egressed participants into the room, the analysis
is conducted in a (macroscopically) quasi-stationary regime. We find that, as
c\_s is increased, the flow rate J rises, interpolating between published
values for egresses in normal conditions and measurements for competitive
evacuations. The dependence of several flow properties on the pedestrian
density $\rho$ at the door, independently of c\_s , suggests that
macroscopically the behavioural aspects could be subsumed under the density, at
least in our specific settings with limited crowd pressure. In particular,
under these conditions, J grows monotonically with $\rho$ up to "close-packing"
($\rho$ $\approx$ 9 pers/m${}^2$). The flow is then characterised
microscopically. Among other quantities, the time lapses between successive
escapes, the pedestrians' waiting times in front of the door, and their angles
of incidence are analysed statistically. In a nutshell, our main results show
that the flow is orderly for polite crowds, with narrowly distributed time
lapses between egresses, while for larger c\_s the flow gets disorderly and
vanishing time lapses emerge. For all c\_s , we find an alternation between
short and long time lapses, which we ascribe to a generalised zipper effect.
The average waiting time in the exit zone increases with its occupancy. The
disorder in the flow and the pressure felt by participants are also assessed.
