Driving activities in Longest Path

Recently, the planning team hit the panic button to bespeak the management attention on the schedule delay. This in return lead to project recovery meeting. The meeting was well intended but misguided with the concept of revising to a new schedule date for ALL the delayed activities. Whole team was about to engage with knotty task of devising turnaround strategy,

We stand divided as the planners are displaying the Longest Path and advised the management and the team to perform recovery on the activity that driving to the delay of Project Completion or the Mechanical Completion. Someone from the crowd asked me after the meeting what is Driving Activities  in Longest Path.

Performing the ‘forward pass’ CPM calculations to a logical network of activities tells you the earliest time in which a project can be completed. The date each activity is scheduled to begin is known as the ‘Early Start’ and the date that each activity is scheduled to end is called ‘Early Finish.’

Kenji Hoshino at the 2002 AACE Conference explained the problems with the concept of float and proposed that we Scheduling Engineers stop looking at float and start looking at a newer concept called, ‘Longest Path.’

Just like the CPM, the Longest Path is a process. It finds the last activity in the schedule. It then travels backward using the driving relationships to identify all activities that are related to the last activity via driving relationships. This list comprises the Longest Path.

In his presentation at the AACE Convention in Portland, Mr. Hoshino said that we should look at the Longest Path and not the Critical Path when managing projects or considering the effects of delays. He went on to say that just like the concept of Near-Critical Activities (those activities with a low float value approaching the Critical Path,) we should also consider looking at Near-Longest Path activities as well.

(Source: Longest Path Value (to the Rescue) By Ron Winter Ron Winter Consulting LLC)

What is a ‘Driving Relationship?’ We mean that it has a slack of 0. The relationship exactly fit in between predecessor and successor and there is no room to delay in this particular string of activities.

Task E has three predecessors which are tasks B, C, & D.  As Task B will take longer to complete than the other two below it, the relationship between Task B and Task E has 0 slack. In other words; it is the driving relationship.

How do I identify critical activities, critical relationships, and driving relationships in Primavera P6?

The following visual indicators represent critical activities, critical relationships, and driving relationships:
Activity boxes outlined in red are critical activities; activity boxes outlined in black are not critical activities

Solid red lines represent critical relationships, while solid black lines represent non-critical relationships.

Solid lines represent driving relationships, while dashed lines represent non-driving relationships.