Critical Path Method (CPM) is a lifeline of project management. It is used by business organizations to plan, schedule and monitor a multitasked project. It is one of the network scheduling techniques used by project managers to trace the time line of the interdependent tasks and plan acceleration in case of delay. It also helps them in the analysis of individual activities and design a perfect schedule as per the requirements until the project is completed.
Basically, in an organization multitasked project uses human network to carry out the business plan efficiently. The CPM in fact is an observation and analysis tool of such a network, which shows time, cost and performance of the activities of that project. Based on mathematical algorithm, it can calculate latest time of the ongoing activity in a network and can predict the exact end date of the project.
Any project is easier to monitor if it is divided into work breakdown structures (WBS). That way the total work of the project is distributed evenly into tasks, subtasks or activities. The task is executed when its predecessor completes its work. CPM uses graphical charts to display the status of these activities of the project.
Normally, a task or an activity is denoted in a CPM chart by a circled alphabet along with its duration and connected by arrowed lines to form a network. An arrow indicating the direction of progress is routinely used to represent an activity in the project. The activity shows start and end dates to form a perfect project schedule. A well-designed CPM project chart looks something like this:
To design a CPM project using such a network-scheduling chart, the project needs to be planned carefully. Minimum a project manager needs to design such a network schedule is
- start and end date of the project
- time and budget
- a list of all the tasks/activities
- work resources
- a critical path
When everything is ready, scheduling becomes easier to chart. Simply begin by pointing the start and end date of the project. There are two sets of activities here – (1) important, and (2) subsidiary. The scheduling can be done in steps as mentioned below:
(1) draw the important activities in alphabetical sequence,
(2) label each activity with its start and end date
(3) form a chain of interdependent activities using arrow heads.
(4) The activities which are subsidiary to the project and are not interdependent should be listed in separate chains.
Finally, determine the critical activities amongst all the tasks of the project and draw the critical path using red line for extra focus. An activity is critical if a delay in its start results in the delay of the project and is the longest one to complete. It is the most vital part of the CPM chart scheduling which affects the completion date of the entire project. Hence, it has to be determined in advance before the charting begins.
The CPM diagram given here gives us a fair idea of how a project is planned and scheduled in the network. The chart marks out the tasks, which are part of the project, in alphabetical listing of circles along with their time span. Every task is expected to be completed in that allotted duration.
The activities under A,C,D and F are vital to complete the project on time. Hence, they have to be completed in less time than the tasks marked B and E. That way the route belonging to the tasks A,C,D and F form the critical path of the project. It remains in constant focus all through and has to be updated every now and then whenever there is a change in the activity status of the project.
This way we can design a CPM chart and monitor the network scheduling of a project. The technique is quite useful to analyze the dependencies between the all the activities in the network. Project managers can therefore determine the latest time and completion time using the CPM chart entries. It also helps them complete the project on time.