The Critical Path Method (CPM) - Construction Project Scheduling and Control - page 63

4. If all paths in a network must go through one particular activity, this activity
must be critical (e.g., activities A and G in example 4.1).
5. Some people like to define critical path as the path with zero float. This defi-
nition is correct only if no imposed finish date is used in the backward-pass
calculations (again, this point is discussed later). However, our definition—the
longest path in a network, from start to finish—is more appropriate because
it is always true. We can also say that the critical path is the path with
least float. 6
Tip Box 4.8
Near-critical activities may be as important as critical activities.
Driving and Nondriving Relationships: Activity E in example 4.1 has two pre-
decessors: B and C. We observe that the relationship coming from activity B is the one
that controls the start of activity E. The relationship coming from activity C has no
bearing on the starting of activity E. In this case, we call the relationship from activity B
to activity E a driving relationship . Conversely, we call the relationship from activity C
to activity E a nondriving relationship . Similarly with activity G, the relationship from
activity D is driving, while the relationships from activities E and F are nondriving.
Tip Box 4.9
Contractors: Don't accept unrealistic durations demanded by owners. Don't over-
promise; otherwise, you will underdeliver!
Definitions
Activity, or task: A basic unit of work as part of the total project that is easily
measured and controlled. It is time- and resource-consuming.
Backward pass: The process of navigating through a network from end to start
and calculating the late dates for each activity. The late dates, along with the early
dates, determine the critical activities, the critical path, and the amount of float
that each activity has.
6 Think algebraically; TF =−8islessthanTF= 0.