Two of my published books, “Risk-based Management in the World of Threats and Opportunities: A Project Controls Perspective” and “Plan to Schedule, Schedule to Plan,” described the Critical Path as a network of linked schedule activities that determine and control the entire project’s completion time.
Delay to any activities sitting on the primary critical Path will delay the finish date of the whole project. Any activity sitting on it is vital, even if its duration is only one day or one second. Note, however, that for many years, the introduction of the terms “secondary critical path, tertiary critical path, and up to the nth path” forces one to be clear when using the term. In this write-up, we refer to the Primary Path when discussing criticality unless described explicitly as another.
Identifying activities belonging to the primary critical Path using the Primavera tool has three general settings, i.e.:
- Longest Path.
- Total float equal to or less than zero.
- Path with the lowest Total Float (can be positive, zero, or negative).
- Whatever the contract defines it to be.
The fourth one depends on how the governing contract defines critical. If the agreement says all activities with a Total Float of less than 10 days are critical, then it is. All parties must respect that. The definition of near-critical activities follows the same gist.
What about the third item regarding the Path with the lowest TF and the fourth one described as the “it depends” Critical Path?
We automatically tackle the former each time we discuss items 1 and 2. The latter considers activities as critical depending on how the client perceives the task, i.e., regardless of floats or paths. No question is asked if the client feels it is essential to him. The activity becomes part of the critical priority list. It becomes as important as the others on the primary Path. It becomes part of the contract. This is a criticality based on the client’s perspective.
Critical Path measures schedule flexibility, discernable through each activity’s total float. On any network path, flexibility is the positive difference between early and late dates (PMI, Project Risk Management, 2013). It is the shortest time possible for a project to finish.
Relative Critical Path
“Be careful of relative critical Path. This is the critical Path relative to some select constraint points only.”
“The Path it generates does not represent the overall project’s critical Path. The true Critical Path of the schedule is generated by calculating, without date constraint, or by calculating a network that flows freely.
Multiple projects linked using external dependencies or cross-project links in P6 create constraints when the schedule is opened individually. All the tied project schedules must be open as one schedule to release the restrictions.
The Project Manager must understand his constraints to effectively manage the project. Once he knows, he can plan the best approach to address the associated challenges and costs. He can say what makes good sense and which does not.
Anything that prevents the forward and backward pass calculations makes the resulting critical Path a bunch of broken Paths that only make them questionable.
Unless the exercise is to study a what-if scenario identifying the schedule drivers that push specific dates. A “relative critical path” can end up misleading the whole team.
A constrained activity limits the full appreciation of the overall critical Path. It can mislead planners and schedulers to the wrong Critical Path. It creates a barrier that prevents the normal logical schedule flow. It causes missed opportunities and poor risk management decisions if not appropriately handled (Frago, R., 2015).
Difference between the setting “Longest Path” and “Total Float is equal or Less than Zero.”
One must know that the longest Path and the total float equal or less than zero represent the Critical Path. This knowledge is vital for one to appreciate the difference between them. We have to understand sameness to comprehend differences.
I have encountered many self-proclaimed planning/scheduling experts in the construction industry. The concern is when the discussion revolves around the critical path fundamentals; more than half cannot explain its essence. They need to have that picture-perfect impression of what it really is.
Does this mean that the term critical path is but a salesperson’s word?
How can we trust a project manager, a project specialist, or a scheduling expert who does not know one of the most important aspects of scheduling and good project management?
Concluding Statement
As the scheduling tool is the vehicle to get the project where it wants to be while following the processes required for managing time effectively, the responsible planning and scheduling person must use the tool correctly.
Knowledge of the tool leverages the effective implementation of the processes involved and vice versa. We should not discount any of them. Implementing management processes using tools like Primavera, SAP, PRISM, and the like only means that the toolset is as vital as the knowledge of a project person about his processes.
Pencil pushers and computer jockeys do not know what is happening. Still, they are moved only by transferring listed data into the system. They are not tool experts. They will likely harm the company in time if you have them in your organization.
The project needs personnel who understand why they are doing what they do. Therefore, the Project Control Manager and the Project Manager are responsible for selecting the more knowledgeable person from the ordinaries. They have to choose an excellent one from the mediocre. They should know exactly the questions they asked, not rely on seemingly clever answers that are actually empty discourse.
They are also responsible for educating the rest with the knowledge of the few. Collaboration and knowledge sharing are keys to keeping the project safe using the much-neglected planning and scheduling processes.
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BOOKS AUTHORED BY RUFRAN FRAGO
- Risk-based Management in the World of Threats and Opportunities: A Project Controls Perspective.ISBN 978-0-9947608-0-7.Canada
- Plan to Schedule, Schedule to Plan.ISBN 978-0-9947608-2-1.Canada
- How to Create a Good Quality P50 Risk-based Baseline Schedule.ISBN 978-0-9947608-1-4.Canada
- Schedule Quantitative Risk Analysis (Traditional Method).ISBN 978-0-9947608-3-8.Canada
- RISK, What are you? The Risk Manager’s Poem: Children’s Book for all Professionals.ISBN 978-0-9947608-4-5 (Canada)