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Resource leveling versus resource smoothing
The reason we’re looking at this topic is sometimes these items you can get confused when you’re doing the PMP exam, so it’s a good idea to understand it out before going into the exam in case you get a question on these two items on your project schedule.
What is resource optimization in general? It is used to adjust the start and finish dates of activities, we’re adjusting the planned resource use to be equal to or less than the resource availability – because we don’t want to be using more resources than we actually have. We might need to level or smooth those resources out.
Resource Leveling and Resource Smoothing
These are the two techniques used. Leveling focuses on moving the resources themselves while smoothing focuses on moving the activities within your critical path, using any existing float.
You might be familiar with some of those terms but we’ll go into a few examples and that should make it a little bit more clear.
Resource leveling can be used when shared or critically required resources are over allocated, such as when a resource has been assigned to two or more activities during the same time period. So obviously unless you can clone that person, if the same person is assigned to two activities in one time period then they probably can’t get one of those things done. So we just need to level that out.
When we’re resource leveling it can often cause the original critical path to change. As you can see in the first example, we’ve got Sue and Tom performing activity A, but we’ve also got Sue again performing activity B in the same time period. So again, unless we can clone Sue (which I don’t think is possible quite yet) we may have to shift that activity so that Sue is not doing those two things in the same time period. Then we’ve got the the third one over here that seems to be clear – it’s just one person doing that activity.
After resource leveling during day one we’ve got Sue and Tom doing their activity A, then we’ve got Sue doing her activity B on day two, and then Tom moving his out to day three, and this is why we say that the critical path may or will change during resource leveling, because we are leveling out the resources but we’re also extending out the time to suit. We’ve had to level out those resources, so the critical path may change now.
Resource smoothing adjusts the activities of a schedule model within their free and total float. Because of that the critical path is not changed because we’re just using up the available wiggle room in our schedule. Let’s have a look at an example of a schedule network diagram, where you’ve got early start, the duration and the float. Those are the two things that we’re really looking at here. As you can see we’ve got no float on this on this activity, no float on this activity, but we have got five days worth of float or wiggle room on this particular activity, so maybe we can push this back by five days and it will still be okay – things can be smoothed out and it won’t adjust the critical path or our overall schedule.
And that is the idea of resource leveling versus resource smoothing.
– David McLachlan