Plan Lab has developed a new Critical Drag Calculator software program to complement Primavera P6 and significantly improve the efficiency and success rate of your P6 schedule compression efforts.
You need to focus schedule-shortening strategies on those tasks that contribute most to the project’s end date. Large projects, such as those with 4,000 activities, will have several paths. You need to prioritize which critical path to optimize and, within that path, which individual duties to direct your compression investigation on. Much time and exertion is wasted examining ways to shorten tasks that do not materially contribute to the project finish date.
Critical drag measures how much a respective effort contributes to the project duration. Calculating critical drag, however, on multiple parallel paths with varying activity durations and relationship connections is often complex.
This is when the Plan Lab’s Critical Drag calculator comes in handy. Plan Lab’s Critical Drag Calculator generates an Excel spreadsheet list of tasks prioritized by Critical Drag (days). This way, you are directed to efforts prioritized for their potential schedule compression opportunity.
This article discusses scheduling time-saving monetary opportunities, demonstrates how to use Plan Lab’s handy Critical Drag Calculator and the utility of the Critical Path Drag metric for prioritizing tasks to shorten.
Financial Benefits of Schedule Optimization
The adage “time is money” is well-worn and practically elusive but valued by proficient project and program managers. Project managers gain an advantage over labor and equipment costs by compressing an activity’s duration.
This does not hold for material costs, which are lump sum upfront costs irrespective of the related job’s duration. However, for labor and equipment, shortening schedule duration directly correlates to cost savings.
Your time-savings and even time-shavings attempts can generate significant cost-savings from less apparent or indirectly correlated costs to the tasks in question. Below is a perplexity-inspired list of indirect financial benefits from schedule optimization:
Cost Savings
- Lowers ongoing administrative and project management overhead costs.
- Enables lower interest expenses on construction financing loans.
Capital
- Reduce theduration of unallocated capital required until work concludes.
- Allows earlier reallocation of capital tied up in the project.
Penalties
- Elimination of late fee delivery penalties in contracts.
- Avoidance ofliquidated damages for missed deadlines.
Revenue
- Limit daily losses from not having a fully functioning revenue-generating facility.
- Earlier realization of project benefits and return on investment.
Resource Allocation
- Ability to reassign resources to other profitable projects sooner.
- Reduced opportunity losses or increased costs because of tied-up resources.
The problem is that the effort to save project time often costs more money in time than necessary. And you do not want your compression plans to cost more than the opportunity.
Further, you may not achieve any time advantage and, therefore, return on investment at its conclusion. Here, your schedule-shortening plan was unhelpful.
Demonstration – how to use Plan Lab’s Drag Calculator
We have in Figure 1 our demonstration project schedule.
Figure 1
This schedule has several critical activities with zero total float and other non-critical tasks with total float. These non-critical assignments can be delayed by days equivalent to their total float without postponing the project end date.
Plan Lab’s Drag Calculator is located here.
Figure 2 displays the Critical Path Drag Calculator on the webpage.
Figure 2
To begin, (1) enter your email address and (2) click the access tool button, Figure 3.
Figure 3
The Drag Calculator is now ready for use. As displayed in Figure 4, click the document icon and locate your file.
Figure 4
If your file upload is successful, it will appear in the lower-left corner of the drag calculator screen, Figure 5
Figure 5
In Figure 5, (1) Confirm your uploaded file, and (2) click the “Compute and get drag table” button. Then, locate the Drag-Calculator-generated Excel spreadsheet in your downloads folder.
In Figure 6, we click the Brief tab in the Excel workbook and note the column lists of Activity IDs and names from our schedule with Duration (days), Drag (days), and Float (days).
Figure 6
The task list, Figure 6, is prioritized by descending from the most considerable drag duration. The prioritized list of drags tells you which activities to optimize and in which order of significance.
In Figure 7, we have the same information and the Reason for the drag value, whether it Has reverse critical path drag and the Driving paths.
Figure 7
The Critical Path Drag Calculator webpage has an Introduction to Drag writeup and an example of “reverse critical path drag” to help you understand this special case. With the drag calculator, schedule compression becomes an iterative process. You compute and get a drag table.
Then, from this prioritized descending list of drag, you investigate shortening the duration of tasks with the most significant drag. Onward, you recalculate the schedule and begin the next iteration by computing and retrieving the prioritized drag table.
The drag calculator functions like that handy calculator: for each iteration, you have it compute the drag of each task and order them by impact. The drag calculator is a significant efficiency improvement that supports the schedule compression process.
It does not eliminate the need to confer with the project’s technical expert. However, it focuses your attention on those assignments that can result in the most significant schedule shortening.
Utility of the Critical Path Drag Metric
Stephen Devaux developed the metric and term drag for schedule optimization. He wrote about it in his 1999 book (updated in 2021) Total Project Control: A Manager’s Guide to Integrated Project Planning, Measuring, and Tracking.
Devaux says that his drag metric was inspired by George William (Bill) James’s baseball statistical “sabermetrics,” which Bill began writing books about starting in 1977 and onward. Bill’s approach is a statistical way to evaluate and compare the performance of individual baseball players.
The movie Moneyball with Brad Pitt retells the “Cinderella” success story of the Oakland A’s 2002 season and their application of sabermetrics to form the roster of their underfunded baseball team. I remember from seeing the movie that the A’s managers were not as excited about a player’s batting average as their on-base percentage (OBP), the ability to get on base, even from the inglorious result of the pitcher throwing four balls.
Likewise, a project manager should not be as concerned about critical task duration as critical drag. Usually, a scheduler’s initial thought is to shorten the duration of the most extended critical activities, but this doesn’t always provide the most optimization. Devaux discovered that you must take simultaneous or parallel operations and their float (and even lag) into account on the Gantt chart.
He coined drag, a less obvious metric that better measures an activity’s true impact on the schedule’s end date. The effect of these parallel tasks and their float (and lag) is easily explained for simple schedules. However, this drag metric computation becomes more complex for schedules with varying relationship types. Hence, your need for his drag metric calculator.
Summary
For the first time, schedulers using the most popular scheduling software platform, Primavera P6, have an effective way to measure critical drag in their complex schedules. This should improve efficiency and win attempts for efforts to compress the schedule.
The optimization process is iterative, each consisting of shortening the tasks having the most critical drag and rescheduling the project. The critical drag metric does not eliminate the need to consult a subject matter expert for the task’s critical drag compression plan.
Still, it focuses schedulers and project managers on the activities where the most significant improvement to schedule duration is likely achievable. Consider the financial benefits we listed earlier for a shortened schedule. Implementing the critical drag metric and calculator, along with technical expert consultation, is the best way to optimize the schedule to avoid or reduce financial costs.
You will find that the critical drag calculator is indispensable in your scheduling toolbox, especially for large projects. Major League Baseball (MLB) teams attempting to win the World Series applied (statistical) sabermetrics to their 2024 player acquisition efforts. These team rosters cost, on average, 200 million dollars.
Could project managers with, perhaps, less televised but important and, possibly, lifesaving projects and similar budgets learn from MLB teams’ use of good metrics proficiency?
A Wikipedia article on Critical Path Drag is here.
You may be interested in reading Understanding Schedule Critical Path Drag.
We also have a review of Stephen Devaux’s book Managing Projects as Investments.
For a primer on the computation of the drag metric, refer to the Drag Calculator website cited above or this YouTube video.
