Resource critical Path

Khawaja,

The RCP is the subset of tasks that determines the project duration in a schedule with limited resources where the schedule has been resource workload leveled. The RCP can have logical dependencies but also resource dependencies. A resource dependency happens when one person needs to do two fulltime tasks and one of them is delayed to start after the other. Most project scheduling applications can perform resource workload leveling, but only some can also identify the RCP as well (Spider). For Microsoft Project, we developed an add-in that can determine the RCP in a Microsoft Project schedule; it is called 'PathsPro' and can be found on ProjectProCorp.com. 

You can also find articles 'Take the Path that is really Critical' and our textbooks 'Forecast Scheduling' on the topic of RCP on our website: ProjectProCorp.com 

Hope this helps.

Eric Uyttewaal, President ProjectProCorp

Anoon,

I don't like the term Resource Leveling and prefer Resource Constrained Scheduling.

The task you described means creating good project model and optimizing the numbers of people and equipment required for finishing project to expected time. We have done this for projects in remote locations (pipeline construction as an example).

Vladimir, Yes, resources shall of course follow activity logics. When several activities using the same resources occur at the same time (as scheduled), then resource-overload happens. This for me simply means that tasks-scheduling is poor in the first place. Imagine a remote project where you sourced-out your resources (or manpower) from several continents for example. This alone is so difficult where I guess most large organizations just rely on manpower agencies. And all you can do is estimate or guess the necessary resources as precise as you can. Otherwise, a single mistake can simply become a disaster. You may need to adjust your activities as often, simply to accommodate your very limited resources. So for me, to use "retained logic only" in a working schedule is never a "best practice". And why not just say: "Activities Leveling" instead of "Resource Leveling"?

Anoon,

resource leveling allow for all logical dependencies and task priorities.

But out of sequence in resource leveled schedule may mean different order of activity execution though without violation of dependency links.

Wow! A post from 2007 and perhaps may shed-light to: WHY MOST (IF NOT ALL) SCHEDULES ALWAYS GO OUT-OF-SEQUENCE? 

What's the difference between Activities or Tasks scheduling only (with no resource loading), as compared against a fully-resourced loaded schedule? (Which I guess seldom literally used in real construction world). 

And how can you exactly schedule and level resources without reference to activities or tasks priorities for example? 

I believe CPM calculations were always derived from tasks-logics and durations. 

While "resources" are of course always limited and were just assigned to pre-defined sequence of activities or tasks. 

Any changes to resource loading (leveling for example), shall of course significantly impact the tasks or activities-sequencing. Therefore the schedule will surely go out of sequence. 

khawaja,

in most PM packages you can schedule or level your project. Scheduling means that resource constraints are ignored, leveling means taking into account resource constraints.

Traditional Critical Path is calculated without considering resource limitations during project scheduling.

Resource Critical Path is calculated during project leveling.

I know for sure that Spider Project calculates Resource Critical Path, other PM software (Primavera, Open Plan, MS Project) don’t do it.

I expect that Critical Chain software also calculates Resource Critical Path because it is almost the same as Critical Chain, but did not try it.

Regards,

Vladimir

If resources are constrained (or limited) activities may be postponed because necessary resources are busy performing other activities.

So one activity can follow another activity not because there is FS link but because they use the same resource.

I agree with you that resources are always limited. Some resource limitations cause activity execution delays.

As the result the longest path in the schedule may consist of activities that are not linked with each other (unlike traditional Critical Path). This is resource Critical Path. And delays of activities belonging to RCP will delay project finish.

Is it clear? If no, let me know I will describe it in more details and with examples. Look at the presentation for more details also.

Best Regards,

Vladimir

Vladimir wrote: "Resource Critical Path consists of activities that cannot be postponed without delaying project finish".



What do you mean by unlimited / limited resources? and activities that cannot be postponed? Do you mean these are constrained activities?



I believe that resources are quantifiable and there’s no such thing as unlimited resources.



I don’t see a reason why the Resource Critical Path might be different from the Activities Critical Path when you are assigning resources to activities. The question lies on whether which one did you establish first, the Activities or the Resources?

Resource Critical Path consists of activities that cannot be postponed without delaying project finish.

If resources are unlimited then RCP is the same as traditional Critical Path. But if resources are limited then Resource Critical Path may consist of activities that are not linked with each other by logical constraints, one activity may follow another just because both use the same resource.

In the simple case when supply and financial constraints are not considered RCP is the same as Critical Chain.



So RCP differs from classical Critical Path only in resource loaded schedules when resources are restricted.



You can read more in http://www.spiderproject.ru/library/london.ppt



Best Regards,

Vladimir