March 9, 2013 3 Comments
The critical path represents the longest (in duration) network of tasks between defined start and end points. The critical path is what determines the total duration of the project. Therefore project managers often draw the logical conclusion that if they diligently manage the series of activities on the critical path, they will ensure that the project is delivered on-time. In my experience, the critical path is a great place to start in terms of analyzing and understanding the project schedule, however there are several pitfalls associated with becoming too focused on managing the critical path:
1. Secondary Paths – Within most project schedules there are alternative networks of activities that are almost as long as the critical path. All it takes is a few adjustments to the plans (i.e., new tasks, or changes in activity sequencing), or variances within the actual execution of the plans (i.e., delayed start of a task, or extended duration of a task), to cause one of the alternative activity networks to become the critical path.
2. Where is the Work? – The critical path represents the longest series of networked activities, but it does not necessarily represent the one requiring the most effort (work) to complete. Generally the network of activities that requires more resources and effort to complete has more risk associated with it. It is not prudent for the project manager to ignore project components that require significant resources and effort.
3. Critical Path Changes – As discussed in pitfall #1, the critical path will change throughout the planning and execution of the project. Changes to any one of the three key elements of the project schedule (tasks, durations, and sequencing) will have a potential impact on the critical path. As a result, it is important that the project manager has the ability to identify and track the critical path on an on-going basis throughout the project life cycle.
These pitfalls highlight the fact that the critical path represents an important data point to monitor and manage throughout the project life cycle, but not the single data point to manage when performing schedule management related functions.
Using MS Project to Identify the Critical Path
As the project schedule is created and updated, MS Project will calculate the critical path, and flag the tasks on the critical path (using the “Critical” field to flag the tasks on the critical path). MS Project provides multiple ways to view / track the activities that it has calculated to be on the critical path. Below I describe the ways that I find the most valuable to manage the critical path throughout the project life cycle.
Filters – One of the filters available within MS Project views is “Critical” tasks. Selecting this filter limits the tasks displayed within the view to the tasks on the critical path.
Select “Critical” Tasks filter
Display only the tasks on the critical path. The “Yes” / “No” flag identifying critical path tasks is maintained in the field named “Critical”.
Group – The Group feature on the view menu provides the ability to group the critical and non-critical tasks.
Select Group by “Critical” Tasks
Tasks are grouped based on those identified as critical vs. non-critical.
Network View – The network view provides a Pert Chart depicting the activity sequencing, and has the ability to highlight the critical path activities within the overall network diagram. I find this view a bit cumbersome to use for projects that are of significant size and complexity. Note: The engineers I work with seem to prefer this view.
Critical tasks are highlighted in Yellow within the Network View.
Gantt View – There are a couple ways to modify the Gantt View to highlight tasks on the critical path. Because this is the view that I use the most when creating and updating the project schedule, I find this technique to be very useful. Critical tasks can be highlighted within the Gantt view by adjusting either the text styles or the Gantt Chart format.
Select Critical Tasks, and change the text color, style, size or background to highlight the tasks on the critical path.
Critical tasks are highlighted based upon the text options selected.
The Gantt Chart tool provides the ability to highlight critical tasks on the Gantt Chart (timeline).
Critical tasks are highlighted in Red on the Gantt Chart (timeline).
Using Slack to Identify “Hidden” Paths
The slack field is utilized to identify tasks that are “close” to the critical path. Slack represents the float associated with each individual task – the number of days the task can slip without impacting the end of the project. Slack is captured within MS Project for both the Start Date and the Finish Date, but I find it is only necessary to track Finish Slack for purposes of managing “alternative” network paths within the project schedule.
In this example task #46 is 5 days from the critical path, but this task requires significant duration and effort to complete (and is likely rated as a high risk task). In reality, my coaching for this project manager would be to break task #46 into multiple tasks with more manageable work efforts and durations.
4 Tips to Effectively Manage the Critical Path
Based upon my experience, managing the critical path is not an exact science. The project manager must continuously take a “holistic” view when creating and updating the schedule, and not become too focused on managing the tasks on the critical path. However, the critical path does provide valuable insights into the tasks that are driving the current project end date. MS Project provides tools that make it easier to identify and understand the tasks on the critical path. Below are 4 tips that I leverage to more effectively manage the critical path and improve project delivery outcomes.
1. Tracking throughout the Project Life Cycle – As previously mentioned, the critical path can potentially change every time you update future plans or actual results within the project schedule. Therefore processes and tools should be put into place to track and manage the critical path every time the schedule is updated. I will generally create a Gantt view that highlights the critical path tasks (either within the task list, or the Gantt Chart). This approach provides the ability to at a quick glance understand the impact of schedule updates on the critical path.
2. Assessing the Critical Path – After each schedule update, the project manager should analyze and rationalize whether or not the tasks listed as “critical” in the project schedule are indeed the tasks that will likely drive the end date of key milestones and/or the project end date. Key questions during this process include:
- Are tasks on the critical path tracking on-schedule? Are corrective actions required for critical tasks?
- Are tasks close to the critical path tracking on-schedule? Are corrective actions required for any non-critical tasks?
- Are there other there other tasks that are of concern (due to effort or risk)? Are the appropriate risk mitigation plans in place?
3. Actively Mitigate Risk – As risks are identified during the schedule analysis process, ensure that risks are effectively mitigated within the project schedule. This mitigation process may include adding/updating schedule contingencies, updating estimated durations or work efforts, modifying resources, or changing activity sequencing. The risk mitigation process may impact the critical path. I will often implement risk mitigation actions to purposefully place a high risk task on the critical path and provide a higher level of visibility and scrutiny to the task.
4. Managing to Milestones – The focus of critical path analysis should not necessarily be limited network associated with the beginning to the end of the project. In fact in most of my project schedules, the end of the project (e.g., Project Closeout Complete) is not the most important project milestone (e.g., “Go Live” Complete). Therefore it is important to understand and manage the critical path to specific milestones (instead of, or in addition to the project end date). This can be accomplished by creating and linking multiple project schedules, or by performing manual analysis to identify/update the critical path for interim milestones. In my humble opinion, this is an area that could be supported more effectively within MS Project.
What has been your experience with managing the critical path? What techniques / tools have you utilized to understand and manage key tasks and improve project delivery outcomes?