Failure of CPM and PERT in Construction Management
There have been various presentations of networks for various uses, and the construction industry has tried out the CPM
variations with unsatisfactory results mainly due to their incompatibility
to the essence of the construction process.
Failure of the majority of construction
contractors to fully use CPM or PERT or both, and adopt it as a basic
construction management technique, exposes that there is some fundamental
failure in the CPM / PERT
network technique. This unwillingness flies in the face
of a great deal of publicity promoting the use of CPM/PERT approach to
construction scheduling. If some contractors have to provide a CPM/PERT network
in the bid at the request of the client, they usually employ an outside
consultant to do it, pass his fee on to the client as part of the bid, and
continue to manage their project with more appropriate manner.
Only a few people have considered whether or
not the CPM / PERT
model is of good fit to the construction process and of
sufficient fit to be used to increase the efficiency of the people working in
the construction processes.
It is suggested that the basic critical path
network technique is neither a true model nor the best approximate model of the
The concept of CPM and PERT was created in the
military/industrial environment where United States National Security put a low
weighing on cost control and efficient use of resources. The specific project
being planned and controlled was of greater importance than efficient use of
individual resources. In Construction, the normal project is not of national importance,
and each subcontractor is very interested in the efficient use of his resources
on all projects he is working on. This creates a different situation and
environment from that of the origins of CPM and PERT. Put simply, for those who
control the construction resources, minimum consumption of resources on a normal
construction project is more desirable than minimum calendar duration for the
whole project. At the very least, minimizing cost is to be considered as much an
objective as minimizing overall durations.
Just as human bodies usually reject medically transplanted
organ from other non-related humans, there should be little wonder that the
construction industry has, to a large extent, rejected the transplant of CPM and
PERT into its body.
The CPM/PERT concepts, while useful in other
industries, are comparatively foreign to the construction process which has
heuristically evolved over centuries to satisfy the needs of the situation of
construction. It follows that a scheduling concept for construction drawn from
that heuristic analysis to the processes of construction can be more realistic
and thus more useful concept of scheduling for the construction process.
The above is quoted from a published paper by
However, Q Scheduling
- which originated specifically
for scheduling construction projects - does consider both cost control through efficient
use of resources as well as time control in a unique manner derived from the
Line of Balance Technique.
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