The Critical Path Method (CPM) is a scheduling tool used to plan and track projects. It allows tasks to be organized based on their sequence and dependencies. The CPM involves drawing a chart that represents each task as a node with arrows showing the dependencies and sequence. It then determines the earliest and latest start/finish times to identify the critical path - the sequence of tasks that must be completed on time or the project will be delayed. The CPM helps optimize schedules, identify risks, and determine the minimum time needed to complete a project.

1. Critical Path Method

2. Critical Path Method
▪ Scheduling and Project Management tool developed in the 1950’s
▪ Allow us to plan all tasks which must be completed in a project
▪ Aids time scheduling and resource planning
▪ They allow progress towards project goals to be tracked

3. Using the Critical Path Method
▪ Some activities cannot be started until previous activities have been completed
▪ Activities in a critical path method need to be completed in sequence
▪ These activities are known as sequential activities
▪ In addition to these, other tasks can be completed at any time
▪ These activities are known as non-dependent or parallel tasks

4. Drawing a CPM Chart: Step 1
• This can be done using a Work Breakdown Structure
• For each task state:
• The earliest start date
•The estimated time it will take

5. Drawing a CPM Chart: Step 2
Establish sequence by looking at:
• Which tasks should take place before this task happens.
• Which tasks should be completed at the same time as this task.
• Which tasks should happen immediately after this task.

6. Drawing a CPM Chart: Step 3
▪ Each circle/node should show a task within the project;
▪ Each circle/node should give start and finish times;
▪ Each circle/node should be numbered;
▪ The arrows/arcs should the sequence of the tasks;
▪ A description and duration of the task should be written under the arrows;
▪ Arrows should always run left to right

7. Examples of Critical Path Method

8. Drawing a CPM Chart: Step 4
▪ Determining the four parameters of each task in the network
1.
2.
3.
4.
Earliest start time (ES) - The earliest time an activity can start once the previous dependent
activities are over.
Earliest finish time (EF) - ES + activity duration.
Latest finish time (LF) - The latest time an activity can finish without delaying the project.
Latest start time (LS) - LF - activity duration.
▪ The float time for an activity is the time between the earliest (ES) and the latest (LS)
start time or between the earliest (EF) and latest (LF) finish times.
▪ During the float time, an activity can be delayed without delaying the project finish
date.
▪ The activities in the critical path have an effect on the deadline of the project.
▪ If an activity of this path is delayed, the project will be delayed.

9. Benefits of the Critical Path Method
▪ Visual representation
▪ The project plan can be tested to ensure it is well thought out
▪ It identifies key tasks which could cause delays to the project if not completed
on time
▪ It identifies tasks which could be delayed in order to complete other tasks which
are more time crucial
▪ It identifies the minimum amount of time a project will take to complete
▪ It identifies any project steps which can be completed faster in order to
complete the project on time

10. Disadvantages of Critical Path Method
▪ Can be more difficult to understand than Gantt Charts
▪ The time needed for tasks is not as clear as with Gantt Charts

11. More Information on Critical Path Method
This is a useful video which sums the information given in the slides and
will aid understanding of the critical path method
http://www.youtube.com/watch?v=SF53ZZsP4ik

12. Further Reading
▪ Kelley, J. E. (1963). The critical-path method: Resources planning and
scheduling. Industrial scheduling, 347-365.
▪ Leach, L. P. (1999). Critical chain project management improves
project performance. Project Management Journal, 30, 39-51.
▪ Maylor, Project Management. Chapter 7

13. References
▪ Maylor, H., 2010. Project Management. 4th Ed. Chester: Pearson.
▪ MindTools, 2013. Critical Path Analysis and PERT Charts. [Online] Available at:
http://www.mindtools.com/critpath.html [Accessed on 07/11/13]
▪ Margaret Rouse, 2011. Critical Path Method (CPM). [Online] Available at:
http://whatis.techtarget.com/definition/critical-path-method-CPM [Accessed
on 07/11/13]
▪ Tutorialspoint, 2013. Critical Path Method. [Online] Available at:
http://www.tutorialspoint.com/management_concepts/critical_path_method.h
tm [Accessed on 07/11/13]