#PM Time Management—What makes the Critical Path so Critical?

1. Introduction—Critical Path method’s place in the processes

Once the network diagram connecting the activities has been created in the process 6.2 Sequence Activities, and the processes 6.3 Estimate Activity Resources and 6.4 Estimate Activity Durations have been completed, it is time to go to the final planning process in the Time Management Area, 6.5 Develop Schedule.

The key to finding out the accurate estimate of the entire project is the critical path method. The purpose of this post is not to outline this method, but to discuss a little why it is so critical. Of course the length of the project depends on it, which you would think makes it critical enough.

But if studying the PMBOK® Guide has taught me anything, it is that project management is like an ecology, albeit one with processes rather than organisms. What happens in one process will affect all of the others. Knowing the critical path is crucial to managing other knowledge areas as well. That is what I will discuss today.

2. Critical Path and its effect on other knowledge areas

The critical path is the path of activities that has the longest total duration, which gives the shortest possible time the project could be completed within. This statement seems contradictory to some in our study group at first, but it really isn’t. The important point is that any delay on the critical path WILL delay the end date of the project. A delay on a non-critical path will not delay the project until the delay becomes longer than the activity’s float.

Finding out the critical path is important, but finding out those near-critical paths and non-critical paths are important as well. Near-critical paths are those that are very close in duration to the critical path. If the critical path is compressed, this near-critical path may then become by default the new critical path. Non-critical paths are useful for a project because they contain float, which is described above as the amount of time an activity can be delayed before it affects the overall project schedule. By definition, activities on the critical path have zero float because any delay in those activities will affect the overall project schedule.

Project Management Area What effect does knowing Critical Path have?
1. Integration Management When it comes to integrated change control, a critical question for evaluating the change is the effect that that change will have on the project schedule, which can be seen through its changes on activities on the critical path.
2. Scope Management If the scope is to be changed, then its effect on the other two major constraints, time and cost, must be analyzed. The critical path will show if additional activities to account for the additional scope will delay the project.
3. Time Management If you want to compress the project schedule, then the critical path gives you the options of which activities to crash.
4. Cost Management Crashing is where you add resources to an activity to reduce the time it takes to complete it. Conversely, if you need resources somewhere else in the organization, you can remove resources from an activity and delay its completion as long as that activity is not on the critical path.
5. Quality Management If it is necessary to shorten the schedule, then seeing how quality management may reduce time-consuming rework, etc., may assist if those activities are on the critical path.
6. HR Management Those human resources that are less experienced can be put on activities not on the critical path, with the experienced people being reserved for activities on the critical path.
7. Communications Management If you are asked by management, “Why will the project take so much time”, you can answer the question.
8. Risk Management Activities which are on the critical path have an inherit risk in terms of the overall project schedule. Finding ways to reduce risks which may compress that schedule are vital, and the critical path shows which activities need more attention with regards to risk responses and risk prevention.
9. Procurements Management Knowing that a subcomponent that is contracted out is on the critical path will help you work with the procurements manager to design a contract that will give incentives and/or penalties to make sure the subcomponent is delivered on time.

So knowing the critical path and, by extension, what the non-critical paths of the project are, can be helpful in all knowledge areas related to project management. It isn’t called a critical path for nothing.

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