Continuing with our series on Project
Management, let’s take a look at how we can significantly reduce the time
required to complete a project and then begin looking at an alternative project
management method.
As we’ve seen in CPM, task durations are
inflated to protect against Murphy. What
if we could significantly reduce these imbedded safety buffers and still
provide the protection that we need? In
our example from Figure 1, suppose we were able to reduce the estimated
duration by 50 % and still protect against Murphy. In other words, if we could complete the
tasks in 5 days instead of 10 days, wouldn’t this be a quantum leap in project
completion time reduction?
Figure 3 depicts the 50% reduction in
durations of each project. We have just
reduced the time to complete these three projects from 30 days to 15 days, but
can we do this and safely guard against the uncertainty introduced by
Murphy? The answer is yes we can!
Figure 3
Earlier we demonstrated how by simply
eliminating bad multi-tasking, significant gains can be made in project
completion rates, but we still have to address the impact of the Student
Syndrome and Parkinson’s Law. We know that
both of these behaviors work to lengthen the time required to complete
projects. Remember how excess safety is
imbedded into traditional project management plans? Resources estimate task times and add in
their own protection against disruptions caused primarily by Murphy. Knowing that this safety exists, resources
then delay starting work on their tasks until the due date is close. Even if the resources don’t delay the task
starts and finish early, these early finishes are not reported or passed on to
the next resource. So how does CCPM deal
with these two behaviors?
While CPM relies on individual task durations
as well as scheduled start and completion dates, CCPM does not. The focus is no longer on finishing
individual tasks on time, but rather starting and completing these tasks as
soon as possible and this is a major difference. So how does this work? Like CPM, CCPM still gathers estimates on
individual tasks and identifies its own version of the Critical Path. Unlike CPM, CCPM considers competing
resources (i.e. the same resource has to work on different tasks) and makes
them a part of the critical path. Let’s
look at an example of how CPM and CCPM identifies the critical path.
CPM defines the critical path as the longest
path of dependent tasks within a project.
That is, tasks are dependent when the completion of one tasks isn’t
possible until completion of a preceding task.
The critical path is important because any delay on the critical path
will delay the project correspondingly.
Figure 4 is an example of a series of tasks which must be completed in a
project with the critical path highlighted in grey. Traditional project
management determines the critical path by looking at the task dependencies
within the project. Task A2 can only be
initiated after A1 is completed. Task B3
can only be performed after completion of B1 and B2. Task D1 can only be
performed after completion of A2, B3 and C2.
Using CPPM the critical path would have been identified as C1-C2-D1 and
the project completion estimate would have been 29 days (i.e. 8d+12d+9d).
Figure 4
In addition to task dependencies there are
also resource dependencies that CPM fails to recognize. What if, in our example, tasks A2 and B3 are
performed by the same resource? Is the
critical path different? In Figure 5 we
see the new critical path that includes a provision for resource dependencies
and as you can see the new critical path is A1-A2-B3-D1 or 5d+10d+10d+9d equals
34 days. So the minimum time to complete
this project is now 34 days. In our
opinion, this failure to consider resource dependencies is one of the key
reasons why project completion rates are so terrible. The simple implication of incorrectly
identifying the critical path, which we will now refer to as critical chain is that the project team
will never be able to complete their project on time without heroic efforts,
adding additional resources, overtime or a combination of all three. The practical implication of incorrectly
identifying the real critical chain is that the focus will be on the wrong
tasks.
Figure 5
In
my next posting we’ll look at a better way to track a project’s status and how
we can better observe all of the projects in our system.
Bob
Sproull
No comments:
Post a Comment