Scheduling: Critical Chain Method

Something I didn´t found in PMBOK and Rita Mulcahy’s book about this method:

Critical chain project management uses buffer management instead of earned value management to assess the performance of a project.

Critical chain method adds the large amounts of safety time to activities in project buffers to protect due-date performance, and to avoid wasting this safety time through bad multitasking, student syndrome, Parkinson’s Law and poorly synchronised integration.

The identification and insertion of buffers:

Project buffer: inserted at the end of the project network. Any delays on the longest chain of dependant tasks will consume some of the buffer but will preserve the end date unchanged.

Feeding buffers: added to protect the activities synchronization.

Resource buffers: they are set to ensure that the appropriate people and skills are available.

Some notes:
Parkinson’s Law is the adage that “work expands so as to fill the time available for its completion”.

Student syndrome refers to the phenomenon that many people will start to fully apply themselves to a task just at the last possible moment before a deadline.

3 thoughts on “Scheduling: Critical Chain Method”

  1. While buffer management under other names is called schedule margin management, it’s not the same or an alternative to Earned Value.
    On defense programs the needed “protection margin” (buffer) is defined with a Monte Carlo simulator. This margin is then assigned in front of the deliverable. The amount of margin is handed out by the program manager to absorb the natural and unnatural delays.
    A margin burn down plan and resulting chart is part of the weekly status report.


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