The Critical Path Method (CPM) is a project management tool used to schedule tasks and ensure projects are completed on time. It involves identifying all tasks, determining their sequence and duration, and mapping them on a chart to identify the critical path - the sequence of tasks that must be completed on schedule or the project will be delayed. CPM aids in planning, tracking progress, and identifying which tasks are most important to keep the project on schedule. It provides benefits like a visual project plan and ability to determine the minimum time needed to complete a project.

1. Critical Path Method
Project Management

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 therefore need to be completed in
sequence
• These activities are known as sequential activities
• In addition to these activities there are tasks which can be completed
at any time
• These activities are known as non-dependent or parallel tasks

4. Drawing a Critical Path Method Chart
Step 1:
• List all the tasks needed for the project in the plan
• 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 Critical Path Method Chart
Step 2:
• Establish whether the activity is sequential or parallel
• For sequential tasks dependant tasks should be highlighted
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 Critical Path Method Chart
Step 3:
• Draw each task as part of a circle and arrow diagram
• Each circle or node should show a task within the project and give start and finish
times
• The circles are numbered to allow them to be easily identifiable
• The arrows or arcs which run from circle to circle show the activities needed to
complete the tasks
• A description of the task should be written under the arrow, with the duration of
the task written above it.
• Arrows always run left to right

7. Examples of Critical Path Method

8. Drawing a Critical Method Chart
Step 4:
• Identify the critical path
• This is done by determining the four parameters of each task in the network
• 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
The benefits of CPM are:
• 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
The disadvantages of CPM are:
• 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.ht
m [Accessed on 07/11/13]