On construction projects (EPCM) I will normally level resources within their Free Float only. Modern projects are usually so time-constrained by clients that Total Float is usually minimal and lengthening activity durations can produce sub-critical paths easily. Of course - if we could more frequently ’relieve’ the schedule with a realistic project completion date then levelling would be that much easier!

To Paul Harris:

Paul, you suggested several techniques for resource levelling, but none of them can be used in the real projects except the software levelling.

Resourced schedules of construction projects usually consist of thousands activities and thus manual leveling is the hard task that shall be repeated each time when something changes (for an example actual data are entered). It is impossible. Besides it is very unlikely that the resulting schedule will be optimal.

Applying relationships to activities sharing the same resources may lead to unreasonable delays when project data will change (and no project will be executed in full accordance with the initial plan).

The only real method is software levelling. You wrote that
“…this option does not maintain a critical path it should not be used when a contract requires a critical path schedule to be maintained. The Leveling function may be used to establish an optimum scheduling sequence and then Sequencing Logic applied to hold the leveled dates and to create a critical path.”
The software will calculate Resource Critical Path (or Critical Chain). The contracts here may include the agreed contract schedule. This schedule will show Critical Chain and there is no need to add unnecessary links that may prevent to optimize resource usage in future.
In any case the contract schedule and the working schedule that is used for resource assignments are not the same. And resource levelling is necessary for this working schedule.
Do you agree?

To James Barnes:

James,

In the sequence of steps that you decribed you prioritized your works before trying resource leveling applying higher priorities to critical path activities. This may lead to the very poor schedules! I can describe some examples if necessary. You shall use the software capabilities before any manual actions. This way you will be able to compare the results and choose the best solution. You wrote that your software sometimes produce nonsense sequencing. You are lucky if you notice it because it is very hard in the large schedules. In any case manual leveling will not work and using the software is inevitable. Try to find the software that is reliable.
I don‘t understand why to “Constrain dates of levelled items” and then “Remove levelling constraints”? Why do you need not levelled daily updated plan? Daily plans are used for resource assignments and thus they shall be levelled. Team on the ground flexibility may lead to the wrong sequencing with bad consequences.
You wrote that “The problems start to arise if the levelled plan is deviated from too much.” I am sure that it will definitely happen in any project. In any case if you use the schedule for resource assignments you will recalculate it (with resource levelling) daily as we do in construction and turnaround projects.

Regards,
Vladimir

I am intrigued by the fact that Paul (whom I absolutely accept as an expert in these matters) doesn’t have a silver-bullet solution. Damn! I had asked a similar question a few weeks back, but with no substantive response. Paul’s post does provide a nice breakdown of the main techniques that I am aware of.

Which one you choose will depend on the nature of your work, especially as it pertains to how much "Long Float" work you have. My industry is an extreme example. In Equipment maintenance turnarounds, most of the work (overhauling a valve or inspecting a vessel, for example) is achievable independant of the rest of the project. We end up with a few critical or near critical paths (usually a large piece of equipment or a plant modification sub-project) but the majority of the work forms a Critical Mass rather than a Critical Path. Thus we have a LOT of levelling to do.

Paul’s point about constrained dates is correct, that you have issues with maintaining a view on your critical path. Sequencing logic we have found to be unsatisfactory because we just have too much to level and the nature of the logic is difficult to determine during execution (eg; did that valve come out after that pipework because it needed to (Hard logic) or because we chose to sequence it that way (soft logic)) Various parties (not just contractors) love to pick on perceived "incorrect logic" as a reason for plan abandonment, so we try and avoid it except in well defined cases (order of exchanger bundle pulling for example). It would be nice of P3 could flag soft logic links but I’m not aware of a way to do this.

The approach we take;

- Develop all "hard" logic and resourcing
- Decide on specific "soft" logic cases and sequence those
- Prioritise the works. Critical and near critical paths are obviously top, equipment dismantling for inspection is next, equipment reassembly is last (to allow max time for any unforseen repairs). An area or workpack priority is laid on top of this.
- Level following priorities. Ideally this is done manually, but often software based first folowed by a full scope item by scope item check and re-arrange which takes a LONG time but it worth it to avoid nonsense sequencing that software levelling can sometimes throw up.
- Constrain dates of levelled items
- Issue for comment and approval
- Set baseline
- Remove levelling constraints. Thus your target (baseline) plan is levelled but your daily updated plan isn’t
- Daily 3 day lookaheads indicate 3 things;
1. Critical and near critical items
2. Planned works (following the levelled target planning)
3. a list of "logically achievable" work allowing the teams on the ground some flexibility if they come up against a problem with the planned work or (*shock*) finish it early ;-)

This is not ideal but the best we’ve come up with so far. The problems start to arise if the levelled plan is deviated from too much, a "ruck" of planned work appears ahead of the Data date that can only be cleared by relevelling (not an easy thing to do when you’re on a 24 hour update cycle) However, for the Levelled work, we track on an overall earned hours basis by discipline. eg, the fact that you didn’t take the valves out in the levelled order is ok, so long as the valves are coming out at the rate planned. If any specific Scope item becomes near critical due to hard logical constraints, then the updated plan will automagically pick it out as it’s FF or TF decreases.

I’d be interested to hear any other approcaches to Critical Mass planning as it is always the part that bites us in the bum

Chris,

That’s a very interesting topic and requires a deep knowledge of understanding of what the real purpose of resource levelling.

Ref: Project Management—A Systems Approach to Planning, Scheduling, and Controlling, Eighth Edition by Harold Kerzner.
Ref: Project Planning Techniques by Parviz F. Rad
Ref: Project Planning and Scheduling by Gregory T. Haugan

There are two network replanning techniques based almost entirely upon resources: resource levelling and resource allocation.

�� Resource levelling is an attempt to eliminate the manpower peaks and valleys by smoothing out the period-to-period resource requirements. The ideal situation is to do this without changing the end date. However, in reality, the end date moves out and additional costs are incurred.

�� Resource allocation is an attempt to find the shortest possible critical path based upon the available or fixed resources. The problem with this approach is that the employees may not be qualified technically to perform on more than one activity in a network.

In addition to Andrews views, scheduling is not merely the process of assigning calendar dates to the completion of activities of the project, however. It also is the art and science of developing a predicted delivery or completion date for the project by way of developing a logical sequence structure for the project’s activities. The foundation of the scheduling process is the logical sequence of the elements of the schedule network, and this sequence serves as the basis for planning, resource allocation, and resource levelling.

The most common decision rule in resource-levelling heuristics is to allocate resources to critical path activities first, then to the other paths depending on the heuristic chosen. In some project management software, there may be no choice in the matter. Some, for example, give priority to activities based on early start dates, and others give priority to the criticality or amount of slack. The more upscale project management software gives the user several options in choices of decision rules. Many of those systems provide resource levelling, a feature that averages out available resources to determine task duration and generates a levelled schedule for comparison.

Resource levelling provides valuable information to the planner to assist in developing a workable schedule considering the availability of labor resources. A key aspect of critical chain project management is the heuristics used to allocate resources.

The proper setup of WBS & RBS enables to assign more accurate resources for every task/ activity in a network.

Hope this help,

Rodel