Critical Path Method CPM

Critical Path Method - CPM


The Critical Path Method is a step-by-step project management technique for scheduling the activities within a project. This technique is used to estimate the time necessary to complete each activity of the project. The sequence of the scheduled activities that takes the longest time to complete is known as the critical path. The activities making up the critical path are known as critical activities, and rest Of the activities are known as non-critical activities. Defining feature of the critical activities is that there is no buffer (also called as slack or float) available on these activities. Even a small delay in the critical activities reflects directly as delay in the project schedule; hence, it is important to monitor these activities closely. As all the activities of the project need to be completed before the project is considered to be complete, the critical path dictates the project's duration.

From the aforementioned steps, you get the network diagram, which shows:

  • The list of activities to be performed in the whole project
  • The inter-relationship between different sets of activities in the project
  • The time spent to complete the individual activities
  • End points of each of the activities and the whole project

The activities and their duration are modelled in the form of a network. Networks are drawn using Activity-On-Node (AON) method. This method contains the two major components, which are:

  • Activities: They are represented as 'Nodes'. These are actions which consume resources (i.e. time, money, energy, etc.). In Figure A, B, C, D, E, F are called activities.
  • Arrows: They depict the dependencies between the activities. Together the nodes and arrows form the network diagram

Some rules of constructing the network diagram are as follows:

  • Every single activity is represented only once in the network.
  • The length of an arrow has no significance.
  • Activities must follow a logical sequence. It means that before an activity can be undertaken, all activities preceding it must be completed.
  • The network should have only one start event and one end event.

The Above example illustrates how to construct a network.

Advantages of the Critical Path Method

  • The advantages of the critical path method are as follows:
  • It is used to determine the duration of completing the project.
  • It segregates the critical path and non-critical path activities.
  • It helps to direct the focus of the project manager on the critical activities, as any delay in these activities can delay the entire project.
  • It also helps the project manager in making decisions as to where the resources should be applied first.
  • It helps the management to take corrective actions, so as to reduce the maximum time consumed for the activities.
  • It identifies the end point of the project.

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