When it comes to project planning, implementing rules and guidelines is essential, but it’s just the beginning.
To truly create a dynamic, efficient, and successful plan, it is crucial that other activities influence each activity’s start, and the completion of each activity, in turn, influences subsequent activities.
Failure to establish these connections can result in what is known as dangling activities.
Let’s consider an example to understand this concept better.
Example of Dangling Logic
Suppose we have activity Concourse – Brickwork, which has a SS (Start-to-Start) successor with activity Concourse – Wall Finishes.
However, what if Activity Concourse – Brickwork takes much longer than anticipated? This would lead to the following scenario:
With the relationship mentioned above, it is evident that the finish date of Activity Concourse – Brickwork does not affect the overall project schedule.
Is this acceptable? In real-world projects, almost all finish dates have some influence on other aspects of the project.
Having dangling activities, where the completion of an activity does not affect subsequent tasks, is not a natural or desirable situation.
A project with numerous dangling activities can lead to unrealistic forecasts and make it difficult to calculate accurate time delays.
To address this issue, the Project Management Institute (PMI) and the Department of Defense (DoD) propose a rule for avoiding dangling activities:
Each activity should have at least one FS or SS predecessor and one FS or FF (Finish-to-Finish) successor.
While it may not be possible to eliminate dangling activities completely, it is strongly recommended to minimize their occurrence.
The number of dangling activities in a project should be less than 1% of the total activities.
Returning to the rule, it is evident that the FS and SS relationships significantly influence the start dates of successor activities:
The start of Activity Concourse-Brickwork is influenced by its predecessor Concourse-Wall due to the FS relationship.
The start of Activity Concourse-Brickwork is influenced by its predecessor Concourse-Wall due to the SS relationship.
Likewise, the FS and FF successors are influenced by the finish date of the activity:
The finish of Activity Concourse – Brickwork influences the successor Concourse – Wall Finishes due to the FS relationship.
Furthermore, the finish of Activity Concourse – Brickwork influences the successor Concourse – Wall Finishes due to the FF relationship.
In addition to the importance of avoiding dangling activities, there are two other crucial aspects highlighted by this rule:
- The most effective relationship type in both scenarios is FS. As we delve deeper into project planning, you will discover that it is advisable to prioritize FS relationships whenever possible. By doing so, the risk of creating dangling activities diminishes significantly.
- One of the four relationship types is absent from this rule: SF (Start-to-Finish). On another occasion, we will explore the reasons behind avoiding SF relationships. This relationship type is deemed ineffective for influencing and being influenced by other activities.
Establishing strong dependencies between activities is vital for creating a well-structured and efficient project plan.
By minimizing dangling activities and utilizing FS relationships, project controllers can improve the accuracy of forecasts and ensure realistic time delays, ultimately leading to successful project outcomes.
Also, read about When to use FF or SS in Project Schedules?