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]