  For safety reasons, it is important that the design of buildings and public
facilities comply with the guidelines compiled in building codes.The latter are
often premised on the concept of exit capacity, \emph{i.e.}, the mean
pedestrian flow rate through a bottleneck (at congestion). Here, we argue that
one should duly take into account the evacuation time fluctuations when
devising these guidelines. This is particularly true when the narrowing
isabrupt and the crowd may behave competitively. We suggest a simple way to
assess the extent of (part of) these fluctuations on the basis of the
statistics of time gaps between successive escapes through the
consideredbottleneck, which in practice could be garnered by analysing
recordings of future real evacuations or, perhaps, realistic drills (in the
limits of what is ethically possible). We briefly present a test of the
proposed strategy using a cellular automaton model and confirm its validity
under some conditions, but alsodisclose some of its limitations. In particular,
it may severely underestimate fluctuations in the presence of strong
correlations in the pedestrians' behaviours(while still performing better than
only the mean capacity).
