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Does anyone use Critical Chain?

2 replies [Last post]
James Shimmon
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Does anyone use the Critical Chain method of Project Management?
Any benefits/disadvantages?




Stephen Devaux
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Hi, James.

In my many years of teaching and consulting on projects in a wide spectrum of industries, I can honestly say that I have never met any scheduler who "uses" Critical Chain.

That said, I certainly have met many who have read the book and feel that it contains some nuggets. These are mostly points that Goldratt makes which, rather than suggesting new techniques or metrics, serve to better illuminate drawbacks in the ways that projects traditionally get managed. These include:

* The costs of multitasking.
* The fact that almost all project-driven organizations minimize staffing levels to the detriment of more profitable projects.
* The lack of schedule reserve ("buffers") at key merge points and at project conclusion, and the rigorous tracking of such buffers.
* The value of giving schedule incentives to key subcontractors.
* The failure of project management to establish and be directed by a "prime operating metric" (although Goldratt offers no solution to this).
* The importance of having a working plan that is much more aggressive than the baseline plan, and of simply working "as soon as possible".

As to drawbacks, I believe that the main drawbacks are due to the fact that, although Goldratt knows a lot about manufacturing (The Goal, in which he introduced the Theory of Constraints, is excellent!), he has much less knowledge about rigorous project management methods. Instead, he bases his comments on the often-sloppy practices that he has observed.

For example, he shows no knowledge of:

1. The practice of resource scheduling and leveling, that can obviate much of the importance of his "feeding buffers". (Although he’s never explicit, I get the feeling that Goldratt’s schedules are simply CPM schedules where activity duration estimates have been extended by padding and by allowances for multitasking.)
2. The fact that resource scheduling is crucial in order to ever get a handle on the delays being caused by resource shortages (as opposed to those caused by the logic and duration of work).
3. Critical path DRAG and DRAG Cost, and the awareness that buffers, whether at merge points or at the project conclusion, have DRAG.
4. The total unawareness of the importance of ABCP analysis, and its potential benefits.
5. The fact that there can and should be a project management "prime operating metric": project profit (or profitability, tracked through the DIPP). (Primavera’s president Joel Koppelman once observed to me that Goldratt had the right questions, but such Total Project Control metrics as project profit, the DIPP, DRAG and the CLUB were the answers to them.)
5. A failure to deal with, or show any understanding of, earned value, including its shortcomings.

Overall, I feel that there is enough good stuff in Goldratt that, in the graduate course in Advanced Scheduling & Control that I teach at Brandeis University, Critical Chain is required reading, and there is a mandatory paper on the subject.

Fraternally in PM,

Steve D.
Andrew Flowerdew
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Hopefully you can answer a question about critical chain methodology.

In the papers I have read it is promoted as a different and alternative method to CPM. But the same papers mentions the "critical chain" - so how is the critical chain calculated? ie, if the method is different from CPM, how is the critical chain calculated without recourse to CPM mathematical theories?

Although as you stated, it does contain nuggets of wisdom, I have not seen anything within the methodology that couldn’t be carried out using traditional CPM methods. It appears little more than a variation on the same theme.

Eg the use of contingency buffers, what is the real difference, (other than clarity), of separating out or including the contingency in the activity as per traditional CPM methods?

I’m hoping you can shed some new light on this method because having read a few papers I feel I must have missed the point somewhere. To me, dissect a bit what is done in CPM, rearrange it a bit into a slightly different format and you come up with CCT, but nothing revolutionary.