How to Calculate Critical Path Drag in Primavera P6?(FS relationships only)

Last week was a huge response to this post and many of us become aware of the Critical Path Drag and its importance. The purpose of this article is to address the Primavera P6 users to compute the drags in P6 itself, but for FS relationships only. For all other types of relationships is a bit tricky required external applications to solve it(Coming soon at Project XER ) or wait until 甲骨文 Primavera include in its own software. The Current software which computes drag are Spider Project Team , Asta/Elecosoft Power Project & Microsoft Project using BPC logic filters.

Critical Path Drag (CPD):

It is the amount of time that an activity on the critical path is adding to the project duration. Or it is the maximum amount of time that activity is Pushing/Dragging the project end date.

Alternatively, it is the maximum amount of time that one can shorten the activity before it is no longer on the critical path.

Critical Path Drag (CPD) metric is the perfect schedule compression technique used to shortens the project?durations by crashing method.

An exercise posted by Stephen Devaux?"Compute and Use Drag & Drag Cost"

Formula for computing drag

1. If an activity is off the critical path, its drag = 0.

2. If an activity is on the critical path and has nothing else in parallel, its drag = its duration.

3. If an activity is on the critical path and has other activities in parallel, its drag = either its duration or the least total float of the parallel activity, whichever is less.

How to Calculate Critical Path Drag in Primavera P6? (FS relationships only)

1. Schedule must be free from "Dangling Activities"
2. Set Schedule Options "Define critical activities as Longest Path"

3. Add user defined field as "Drag" to record the values.

4. Maintain and Assign Baseline by saving a copy of the current project.

5. Add these columns in activity layout. (Activity ID, Critical, BL Project Duration, Remaining Duration, Variance BL Project Duration & Drag-UDF)

6. Select the critical activity (single activity) make the remaining duration as zero.

(Note: if your schedule is resources loaded don't make remaining duration zero because all your budgeted units will become zero, instead choose the least duration say 0.1 days)

7. Now Run the schedule and notice the changes in Summary of "Variance BL Project Duration" column. The value here is the Drag of an activity for which the remaining duration is mark to zero. Record the same value in Drag column.

8. Reset the remaining duration of the activity equal to BL project Duration, Run the schedule, move to next critical activity and repeat the steps (6, 7 & 8) to calculate the drags of all the critical activities.

This method of computing drag is inspired by Tom Boyle . Watch the Demo Video here.

Also Microsoft Excel Spreadsheet is also developed to calculate Drags for all type of Relationships (Still not released for public use).

Only few other people including Alex Lyaschenko talks about critical path drag and I found his comments insightful.

This important CPD project management metric was developed by Stephen Devaux . Follow him for other important metrics and check his articles related to how proper scheduling can save lives & cost.