2nd Edition

Station Layout 13
Fig. 2.4.
Congestion at the foot of an ascending escalator.
Where the choice of route or exits and entrances exist it is important to
determine the proportion of pedestrians likely to use each and allocate
capacity in proportion accordingly.
The points in a station particularly vulnerable to a rapid increase in
congestion are the platforms, foot of stairs and escalators and ticket halls.
If a service is scheduled to run at two minute intervals in the peak, a
sensible guideline would be to assume that after five minutes delay of any
train some staff intervention would be triggered to control overcrowding.
This translates into a design target of passenger density somewhere between
one quarter and one sixth of that at which complete congestion occurs. In
practice it has been established that movement through restricted spaces
ceases once the density gets to between four and five passengers per square
metre. When passageways are almost empty, average walking speed can be
as high as 80 metres per minute but even medium ‘bunching-up’ to a density
of about two people per square metre dramatically more than halves the
walking speed. In tabular form, the flow of pedestrians through walkways
during differing degrees of crowding, can be as shown in Fig. 2.5.