A few days ago, I had organised a poll on LinkedIn and asked a simple question: Can project duration potentially be reduced by decreasing the duration of non-critical activity (total float >0)?

While the poll is still open, and the final result may still slightly change, it is already clear that half of the responders believe that reducing an activity that is not on the critical path would never change the duration of the project, and another half don’t think so. Most of the project participants believe that they know how the critical path method works, so why is there no agreement on a simple question then?
By organising this poll, I wanted to demonstrate the fact that project management is not as simple as it is presented in project management trainings, and even in global standards or organisational frameworks (PMBOK, NASA, etc.). The courses and standards always simplify reality to make it easier to understand.
Apart from project management, it is hard to find another area where professionals continue to apply simplified methods to solve complex and complicated problems, and real project management is never simple. To pass a project management exam, what you need to know is not the same as what we need to know to manage projects!
A real-life project is not just a list of activities with ‘Finish-to-Start’ type of dependencies, as is shown in almost all books that explain project management methods (incl. critical path method) and techniques.

It also includes:

  • Start-to-Start, Finish-to-Finish and even Start-to-Finish dependencies;
  • Double dependencies;
  • Resource limits;
  • Hard & Soft constraints;
  • Different resource & activity calendars;
  • Lags & leads;
  • Risks & uncertainties.

Even the critical path method may not work as expected when these aspects are taken into account.

Let’s now go back to the question in the poll and find the correct answer. So far, in comments to the poll, there are no examples offered, that would demonstrate how a non-critical activity could potentially reduce the duration of the project. Let’s review a small project fragment:


The fragment contains two linked (Finish-to-Start) activities with different calendars. The predecessor activity “A” has six days of duration and a 5-days (Mon-Fri) calendar. The successor activity has 2 days of duration and a weekend (Sat-Sun) calendar.

The duration of this fragment is 14 days. The activity “A” is not on the critical path as it has four days of the total float. However, if we could reduce this activity to 5 days, the overall duration will be reduced to 7 days:

This simple example demonstrates that in some cases, project duration could be reduced by decreasing the duration of a non-critical activity.
It is just one of the examples of “hidden opportunity” in our schedules. There are many others. Such opportunities often exist, but they are not obvious. Unfortunately, MS Project and Primavera don’t have built-in critical path metrics that could help project teams to identify project opportunities. I am going to explain such metrics in future posts.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma