What is Critical Path in Project Schedule

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You must have made a series of simple activity schedules related to a project. Suppose you have a program or plan to move to a new house.

The following are alternative activities planning that you can make:

1 – Contacting the moving house transport service – 1 day.

2 – Determine the day (discussion with family) – 1 day.

3 – Determine the items to be carried and left – 3 days.

4 – Make a checklist of goods – 1 day.

5 – Cleaning the new house before moving – 1 day.

6 – Install a new home air conditioner – 1 day.

7 – Install a new house trellis – 2 days.

8 – Transport heavy goods on moving day – 1 day.

9 – Transport of light goods – 1 day.

10 – Check if there are items left behind – 1 day.

11 – Contact the old homeowner – 1 day.

12 – Tidying up in the new 1 – day house.

13 – Install new home curtains – 1 day.

14 – Clean the new house – 1 day.

15 – Decorating a new house – 1 day.

To make the schedule above, you first have to determine the duration of each activity first.

After that, you can create relationships between activities.

Selection of the critical path can be made by looking at the sequence of activities that form the longest path.

From the schedule that has been made above, the critical path can be determined as follows:

Critical-Path

It can be seen that on the path marked in red, the total duration resulting from a series of activities on that path is greater than the total duration generated by other paths.

Now look again at the schedule in the following table:

CPM-Table-1

By using the Precedence Diagram Method (forward pass and backward pass), the relationships that can be made from the activities in the table can be seen in the image below:

CPM-Path

From the image above, it can be seen that the critical path is marked with a bold black color.

Also read what is the Gantt chart.

What is Critical Path

From the 2 example schedules above, a temporary conclusion can be drawn about the Critical Path, which is the longest path of the schedule which consists of a series of activities from the beginning to the end of the project.

Here are some observations about critical paths:

  • In every schedule, there must be at least one critical path.
  • The critical path can be more than one.
  • Each critical path must be continuous from start to finish of the project.
  • Exception: when a constraint is set, the path may be critical from the start to the constraint activity or from the constraint activity until the end.
  • Some people define the critical path as a path with a total float of zero. This is true as long as there are activities with a total float of zero from start to finish.
  • Some of them define the critical path as the longest path on the schedule (from start to finish). The definition of the critical path is the longest path is more precise in my view because if the project finish date is made backwards (delay), the path with a total zero float will change to a non-critical path. So the critical path in my view is the longest path with the least number of total floats.

Determining Critical Path on Primavera P6

At Primavera P6 there are two options for determining Critical Path, namely based on the number of Total Floats or based on the longest path in the activities network.

Define-Critical-Path-in-Primavera

To determine a critical path, you can access:

Tools >> Schedule (F9) >> Options

Once the critical path has been determined, close the Schedule Options window and click on the Schedule button.

Image Source: Project Scheduling and Control by Saleh Mubarak.

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