Resource Leveling and Resource Smoothing Explained with An Example

What is resource leveling?

What is resource smoothing?

Are they the same? If not, what is the difference?

We will try to answer the above questions in this article.

Resource Optimization

Resource optimization is a tool/ technique used in the Develop Schedule process of Schedule Management knowledge area.

Resource optimization is a schedule network analysis technique applied to a schedule that has already been analyzed by the Critical Path Method (CPM).

Resource optimization is needed when resources have been overallocated, such as when a resource has been assigned to two or more activities during the same time period. It may also be needed when certain resources (eg. equipment or machinery) are available in limited quantities, while the CPM schedule demands more than the available quantities.

In short, resource optimization is employed when there is a resource conflict (ie. when the schedule requires more than the available resources) or when there is a need to keep the resource usage at a constant level.

Examples of Resource Optimization Techniques

Two examples of resource optimization techniques are:

1. Resource leveling and
2. Resource smoothing

Comparison of Resource leveling and Resource smoothing

Let us see a comparison of the two resource optimization techniques below:

Example to illustrate the difference between Resource leveling and Resource smoothing

Now, let us look at an example and try to understand how resource leveling and resource smoothing works in a project.

Consider a project with 7 activities as shown in the table below. The predecessors of each activity and the duration of the activities are given. The number of compressors (consider it as a resource) required by each activity is also listed. The organization has only 6 compressors available with them.

The first step is to draw the schedule network diagram and determine the critical path.

From the schedule network diagram, you can understand the critical path is A-B-C-E-G and the total duration of the project is 20 days.

The problem with the critical path method is it does not consider the availability of resources. So, now we need to check whether there are any resource conflicts in the schedule created by the critical path method.

It will be easier if we present the schedule in the Gantt chart/ bar chart format to understand the resource usage over time periods.

With the bar chart representation, it is easier for us to calculate the compressors needed on each day. For example, we know that from day 1 to 3, only activity A is in progress; so, we need 6 compressors on each of these days. However, from day 6 to 9, activity C and activity D are running in parallel. So, you need 7 compressors (5 for activity C and 2 for activity D) on each of these days.

Let us plot the resources required as a histogram.

By drawing a line to show the resource limit, we can clearly see the days on which the resource conflict occurs. You can see that the schedule requires more compressors than available on six days; Day 6, 7, 8, 9, 11 and 12.

Now, let us see how the application of resource leveling and resource smoothing helps to remove the resource conflicts on these six days.

Application of Resource Leveling to the Sample Project

As we have seen earlier, resource leveling looks at removing all resource conflicts without worrying too much about extending the project duration.

Let us look at the first conflict, which happens between activities C and D. To avoid the conflict, we need to delay either activity C or activity D. Since activity C is on the critical path, it is prudent to delay activity D.

We have to delay the activity D until activity C completes. This means, activity D has to be shifted to start on Day 11. By doing this, the resources required on days 6 to 9 comes down to only 5 compressors. Since there is a float in activity D, everything looks fine.

But, when we move an activity, we have to see how it affects the other successor activities. In this case, since F depends on the completion of activity D, it also has to be shifted.

Now, you can see that there is no resource conflict from day 1 to day 14. But, there is a conflict on days 15 and 16; activity E needs 4 compressors and activity F also needs 4 compressors.

So, we have to delay either activity E or activity F to avoid this conflict. Since activity F is not on the critical path, let us delay this activity.

We have to delay it until the completion of activity E. It means activity F can start only on day 20. However, it also leads to the shifting of activity G since activity F is its predecessor.

Let us look at the final Gantt chart and the resource usage histogram.

It’s good. All resource conflicts are removed. Now, the maximum compressors required is only six numbers on any day.

However, in the process, the project gets delayed by two days. The total duration of the project is 22 days now.

The critical path also has changed. Activity F is part of the critical path now. So, the new critical path is A-B-C-E-F-G.

Application of Resource Smoothing to the Sample Project

Resource smoothing looks at removing as much resource conflicts as possible without delaying the total project duration.

Let us again start to adjust the original CPM schedule to avoid resource peaks.

Activity D is shifted from day 6 to day 11. This removes the resource peaks from day 6 to 9.

However, there is still resource conflicts on day 15 and day 16. This conflict cannot be removed without delaying the total project duration. So, resource smoothing will stop here.

Out of the six days of conflict, resource smoothing managed to remove 4 days of conflict. However, if the organization wants to stick to the original schedule, they should bring additional resources on day 15 & day 16.

Conclusion

Resource leveling is a resource-limited scheduling technique, while resource smoothing is a time-limited scheduling technique.

You could use either of them in your projects based on the requirements of your organization.

Does this article help you in your understanding of the difference between the two resource optimization techniques, resource leveling and resource smoothing?

If you still have any queries, please leave a comment. I will respond to them.

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Manickavel Arumugam

Certified Project Management Professional (PMP)®
Certified Risk Management Professional (PMI-RMP)®
An enthusiastic project management practitioner and trainer.

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