Resource Leveling Quantitative Effects

Resource leveling refers to the planning methodology in which scarce resources, typically staff with special skills (but also special equipment, facilities, and environments), are allocated to tasks where there is otherwise conflict for the resource. The situation we are addressing naturally arises out of multiple planners who each require a resource and plan for its use, only to find in the summation of the schedule network that certain resources are oversubscribed: there is simply too much demand for supply.

The first and most obvious solution is to increase supply. Sometimes increasing supply can work in the case of certain staff resources that can be augmented by contractors or temporary workers, and certain facilities or environments might likewise be outsourced to suppliers. However, the problem for quantitative analysis is the case where supply cannot be increased, demand cannot be reduced, and it is not possible physically to oversubscribe the resource. Some have said this is like the case of someone wondering if "nine women could have a baby in one month." It is also not unlike the situation described by Fredrick Brooks in his classic book, The Mythical Man-Month, [5] wherein he states affirmatively that the thought that a simple interchange of resources, like time and staff, is possible on complex projects is a myth! Interestingly enough, Brooks also states what he calls "Brooks Law":

Adding additional resources (increasing supply) to a late project only makes it later! [6]

For purposes of this book, we will limit our discussion of resource leveling to simply assigning resources in the most advantageous manner to affect the project in the least way possible. Several rules of thumb have been developed in this regard. The most prominent is perhaps: "assign resources to the critical path to ensure it is not resource starved, and then assign the remaining resources to the near-critical paths in descending order of risk." Certainly this is a sensible approach. Starving the critical path would seem to build in a schedule slip right away. Actually, however, others argue that in the face of scarce resources, the identification of the true critical path is obscured by the resource conflict.

Recall our discussion earlier about correlating or creating a dependency among otherwise independent paths. Resource leveling is exactly that. Most scheduling software has a resource leveling algorithm built in, and you can also buy add-in software to popular scheduling software that has more elaborate and more efficient algorithms. However, in the final analysis, creating a resource dependency among tasks almost certainly sets up a positive covariance between the paths. Recall that by positive covariance we mean that both path performances move in the same direction. If a scarce resource is delayed or retained on one path beyond its planned time, then surely it will have a similar impact on any other task it is assigned to, creating a situation of positive covariance.

Figure 7-11 and Figure 7-12 show a simple example. In Figure 7-11, we see a simple plan consisting of four tasks and two resources. Following the rule of thumb, we staff the critical path first and find that the schedule has lengthened as predicted by the positive covariance. In Figure 7-12, we see an alternate resource allocation plan, one in which we apparently do not start with the critical path, and indeed the overall network schedule is optimally shorter than first planned as shown in Figure 7-11. However, there is no combination of the two resources and the four tasks that is as short as if there were complete independence between tasks. Statistically speaking we would say that there is no case where the covariance can be zero in the given combination of tasks and resources.

Rule it! Begin lib uro.eti uy beginning to wort, on the loftgasL paih


Task 2

Cr rjiul Pun


Rule 02: AUpV PHOuttM first he CnlüaJ Pàlh; frart Chaik iffl^att to C r.Hia1 Pith

TfljK 1 Mj/y. aOiJSys I joJir. SJffitys Task 2

Figure 7-11: Resource Leveling Plan.

Figure 7-12: Resource Leveling Optimized.
Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook

Post a comment