The critical path is at the heart and center of the Gantt chart and scheduling software. Here we examine ways to display the critical path in Primavera P6 Professional. The critical path is an important concept in scheduling. It tells you how long your project will take. It directs you to the activities to shorten or adjust for schedule optimization efforts, i.e. schedule compression efforts.
There is also more than one way to define a critical activity in Primavera P6. Primavera P6 defines critical activities either by their total float value or by longest path inclusion. Critical activities are displayed in red on the Gantt chart. But you will also want to further distinguish if these red Gantt chart bar activities are critical by total float value or longest path association.
This article demonstrates different ways to display critical path activities in Primavera P6 Professional to provide more insight into your schedule situation.
Critical & Longest Path on Gantt chart
We have in Figure 1 our demonstration project.
This schedule has two float paths: one for experimental motor testing and another for analytical motor modeling. Critical activities are displayed in red and non-critical in green. If, however, your schedule looks similar to Figure 2, where all activities are green you may need to adjust your definition of critical activities.
By default critical activities in P6 are defined by total float value. Activities that have total float values equal to or less than zero are by definition critical. As displayed in the Figure 2 Total Float column all activities have total float greater than zero, so they are all non-critical.
The cause of this schedule situation is a must finish by project deadline. The schedule has a must finish by deadline, Figure 3, of 03-July-2018, but the natural network logic finish date, Figure 2, is 29-June-2018, earlier than the deadline.
The good news is you are ahead of schedule. The problem is every activity is green (non-critical), so we do not know which path to optimize for schedule compression. What then can or should we do?
Our schedule optimization effort problem is solved by adjusting the definition of critical activities. In scheduling options set “define critical activities as” to longest path, Figure 4.
Now when we recalculate the schedule our project, including deadline, has one continuous critical path on the Gantt chart, Figure 5.
This tells us it is important to note the definition of critical activities; it is not enough to simply view the Gantt chart for red activities.
If the “define critical activities as” setting is toggled to total float value (zero or less) we may have critical activities that are not necessarily along the longest path. Activities may also be critical due to a constraint. In Figure 6 a Finish On or Before (FOOB) constraint is assigned to the Motor Model Material Properties activity.
Activities upstream of this constraint are displayed in red on the Gantt chart. The red bars indicate that upstream activities cannot be delayed without missing the constraint date. So on the Gantt chart we can display activities in danger of delaying a constraint date and/or the project end date.
We also, as demonstrated above may display all activities along the longest path. Looking at the Gantt chart it may not be readily apparent whether the red activities are critical from a total float value definition or a longest path definition.
Critical & Longest Path Columns
A good way to distinguish zero total float critical activities from longest path critical activities is to display critical and longest path columns in the activities table, Figure 7.
Regardless, of your critical activity definition P6 lists all activities that are along the longest path. The critical column lists all activities that cannot be delayed without delaying either a constraint date or the end date of the project. Using these columns and the total float value critical activity definition provides the best of both worlds: all zero total float valued activities are listed and displayed on the Gantt chart, and all longest path activities are listed in the activities table.
You now know activities in danger of delaying either a constraint or the project completion date, and you also know which activities to shorten or adjust for compression of the longest path.
Critical & Longest Path Filters
A common request of upper management is a critical activity report displaying only critical activities. This report is easily generated by implementing the critical filter (one of several default filters that comes standard in P6), which supports schedule activity monitoring, Figure 8.
There is also a longest path filter to capture all and only activities along the longest path to support schedule optimization efforts.
The Primavera P6 Gantt chart is a valuable scheduling tool that highlights all critical activities. The question then is are these activities critical by total float value or longest path association? Insight into this question comes from noting the definition of critical activities in scheduling options or from listing critical and longest path columns in the activities table.
So, the combination of the Gantt chart and critical & longest path columns in the activities table provides the critical path insight to truly understand the schedule situation. Filters also support generation of total float value and/or longest path critical activity reports. The schedule log file, additionally, lists all activities that are critical in the schedule.