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Chapter 4 Process design 107
is to reduce variability in its processes, which may itself require strategic decisions such as
limiting the degree of customization of products or services, or imposing stricter limits
on how products or services can be delivered to customers, and so on. It also demonstrates
an important point concerned with the day-to-day management of process – the only way to
absolutely guarantee a hundred per cent utilization of resources is to accept an infinite
amount of work-in-progress and/or waiting time.
Short case
Heathrow delays caused by
capacity utilization 6
It may be the busiest international airport in the world,
but it is unlikely to win any prizes for being the most
loved. Long delays, overcrowding and a shortage of
capacity has meant that Heathrow is often a cause of
frustration to harassed passengers. Yet to the airlines it
is an attractive hub. Its size and location give it powerful
‘network effects’. This means that it can match incoming
passengers with outgoing flights to hundreds of different
cities. Actually it is its attractiveness to the airlines that
is one of its main problems. Heathrow’s runways are in
such demand that they are almost always operating at,
or close to, their maximum capacity. In fact, its runways
operate at 99% of capacity. This compares with about
70% at most other large airports. This means that the
slightest variability (bad weather or an unscheduled
landing such as a plane having to turn back with engine
trouble) causes delays, which in turn cause more delays.
(See Figure 4.10 for the theoretical explanation of this
effect.) The result is that a third of all flights at Heathrow
are delayed by at least 15 minutes. This is poor when
compared with other large European airports such as
Amsterdam and Frankfurt, which have 21% and 24% of
flights delayed respectively.
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Simulation models
Simulation in design
Designing processes often involves making decisions in advance of the final process being
created, and so the designer is often not totally sure of the consequences of his or her decisions.
To increase their own confidence in their design decision, however, they will probably try
to simulate how the process might work in practice. In some ways simulation is one of
the most fundamental approaches to decision-making. Children play games and ‘pretend’
so as to extend their experience of novel situations; likewise, managers can gain insights
and explore possibilities through the formalized ‘pretending’ involved in using simulation
models. These simulation models can take many forms. In designing the various processes
within a football stadium, the architect could devise a computer-based ‘model’ which would
simulate the movement of people through the stadium’s various processes according to the
probability distribution which describes their random arrival and movement. This could
then be used to predict where the layout might become overcrowded or where extra space
might be reduced.