What is critical path method?

Critical path definition

What is the critical path method? The Critical Path Method (CPM) is a project management methodology often used by construction project managers to determine the time a project should take from start to completion.

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critical path method refers to a sequence of activities taking the longest overall duration to complete and they determine the project completion time. The tasks along the critical path are critical because delaying any of those tasks results in a delay in the completion of the entire project.

Steps in Critical Path Method

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In critical path method project managers use the steps below to identify the longest path in a network of project tasks that need to be implemented for successful completion of the entire project:

1.   Outline the Project Tasks

Project managers create a list of all possible tasks that are required.

From the outlined tasks, the managers can identify which tasks in a project are the most important and break them down into smaller parts for easy management.

2.   Identify the Tasks Dependencies

Project managers take note of task dependencies and sequences when determining the critical path in the critical path analysis.

Usually, some tasks are dependent on others; hence one can only start specific tasks upon completing other tasks. Therefore,  the managers should identify all task dependencies and schedule them so that no tasks are performed out of order.

3.   Create a Critical Path Network Diagram

In critical path method The project managers draw a critical path network diagram showing which tasks need to be completed and in which sequence.

Mainly, managers create a network diagram showing the sequences of tasks using arrows and boxes or nodes. The arrows point at the subsequent activity. Managers indicate the task ID in the boxes while the task durations are indicated above or below the nodes or along the arrow lines. 

4.   Estimate the Duration Each Task Will Take

in critical path method to determine the time the project will take, managers determine the duration of each activity. Project managers assign timeframes to tasks based on their past experiences.

The durations for the different tasks should be realistic to ensure the entire project will be completed within the estimated timeframe.

5.   Calculate the Critical Path

The longest path in the network is the critical path, and it’s used in determining the duration a project will take from start to completion.

Notably, although the longest path is the critical path, the critical path length is usually based on the overall duration for accomplishing the tasks along that path and not the number of tasks.

To ascertain the critical path and project duration managers use forward pass and backward pass techniques. 

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Early Start and Early Finish

Project managers use the forward pass technique in determining the earliest time a project can start and the earliest date the project can be completed.

To ensure the project is completed at the earliest date possible, there should be no delay in commencing and finishing activities along the critical path.

Late Start and Late Finish

Managers use the backward pass technique to determine the latest time a project can begin and the latest date it can be completed.

Usually, the late start and late finish dates are the same as the project’s early start and early finish dates on the critical path. 

6.   Determine the Project Float

Float, also known as slack, refers to the amount of time a task can be delayed without causing a delay in the finish time of the overall project.

Notably, the activities along the critical path have a float of zero. Delaying any of the activities results in a delay of the entire project. To determine the float for activities along other paths, managers deduct the duration of the next longest path from the duration of the critical path. 

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Uses of Critical Path Method

 The following are uses of the critical path method that make it a crucial project management tool:

  • It enables managers to display project activities systematically based on activity dependencies and duration for better visualization.
  • Breaking down and outlining tasks in a systematic sequence helps project managers appropriately mobilize and allocate resources to complete the projects in time and avoid costly project delays.
  • Using the critical path analysis, managers determine which activities can be delayed without delaying the finish date for the project.
  • Project managers can easily track projects and ensure they are completed on or before the expected time. 
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The critical path method is an indispensable management technique that project managers use in complex projects to create the sequences of tasks necessary to complete a project.

Read our Previous article of PERT analisis.

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