Critical Path Method

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

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

Drawing a CPM 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

Drawing a CPM 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.

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

• DRAW EACH TASK AS PART OF A CIRCLE AND ARROW DIAGRAM

Examples of Critical Path Method

Drawing a CPM Chart: Step 4

▪ Determining the four parameters of each task in the network 1. Earliest start time (ES) - The earliest time an activity can start once the previous

dependent activities are over.2. Earliest finish time (EF) - ES + activity duration.3. Latest finish time (LF) - The latest time an activity can finish without delaying the project.4. 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.

• IDENTIFY THE CRITICAL PATH

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

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

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

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

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.htm [Accessed on 07/11/13]