Can a project have 3 critical paths?

March 20, 2019 By

Microsoft Project has a great feature that allows you to display a critical path for each independent network of tasks within a project. This comes in handy when you want to display a schedule Contract Completion Date (CCD) milestone.

Some scheduling guidelines require a separate milestone for the CCD. Schedulers in Microsoft Project can define a CCD milestone and constrain it to must finish on a particular date. The problem with this approach to displaying a deadline on the Gantt chart is that you lose your critical path.

Fortunately, Microsoft Project has an option to calculate multiple critical paths that sets the scheduling software to display a critical path for each independent network of tasks within the project.

This article provides a quick tip on how to insert a CCD milestone using the option calculate multiple critical paths in Microsoft Project.

Below in Figure 1 is our demonstration schedule.

Figure 1

This is a schedule that has two paths: one critical and one non-critical. We want to insert a CCD milestone in compliance with scheduling guidelines. In Figure 2 we insert a CCD milestone task.

Figure 2

We continue and place a Must Finish On July 3rd, 2019 constraint on this milestone, which is the CCD of the project.

Figure 3

When we insert this constraint on our CCD milestone, Microsoft Project sets the late finish date for our Project Complete milestone, a task without a successor or constraint, equal to the project finish date or CCD. This generates 3 days total slack on our critical path, and makes it non-critical, Figure 4.

Figure 4

So we lose our critical path when we insert the CCD constrained milestone. What happened?  Again, by default Microsoft Project sets the late finish date for tasks without successors or constraints (i.e. dangling tasks) to the project finish date. The late finish date of the Project Complete milestone becomes the project finish date, which in our demonstration generates 3-days total slack on this completion milestone. And the associated network of tasks becomes non-critical.

To regain our critical path we can set the advanced schedule option in Microsoft Project to Calculate Multiple Critical Paths, Figure 5.

Figure 5

Now when Microsoft Project calculates the schedule we find our critical path, Figure 6.

Figure 6

When we chose to Calculate Multiple Critical Paths, Microsoft Project set the late finish date for our dangling Project Complete milestone to be its early finish date, making it critical.

Summary

It’s important to maintain one continuous critical path through the schedule network. This becomes a challenge when we insert a CCD constrained milestone. What happens is the CCD becomes the late finish date for tasks without successors or constraints, making the associated network of tasks non-critical.

This situation, fortunately, is remedied by setting the advanced schedule option in Microsoft Project to calculate multiple critical paths. This setting sets the late finish date of dangling tasks to be their early finish date, which makes them critical.