Critical chain

The critical chain, in project management, is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources.

If resource availability is not a constraint, then a project's critical chain becomes the same as its critical path (just like Einstein's theory reduces to Newton's under conditions of low speeds and gravity).

It is an alternative to critical path analysis. The main features that distinguish the CC method from the critical path are:

1. The use of (often implicit) resource dependencies. Implicit means that they are not included in the project network but have to be identified by looking at the resource requirements.
2. Lack of search for an optimum solution. This means that a "good enough" soulution is enough because:
   1. as far as I know, there is no analytical method of finding an absolute optimum (i.e. having the overall shortest critical chain)
   2. the inherent uncertainity in estimates is much greater than the difference between the optimum and near-optimum ("good enough" solutions).
3. The identification and insertion of buffers:

• project buffer
• feeding buffers
• resource buffers.

It aggregates the large amounts of safety time added to many subprojects in project buffers to protect due-date performance, and to avoid wasting this safety time through bad multitasking, student syndrome, and poorly synchronised integration.

Critical chain project management uses buffer management instead of earned value management to assess the performance of a project. The earned value management technique is thought to be misleading, because it does not distinguish progress on the project constraint (i.e. on the critical chain) from progress on non-constraints (i.e. on other paths).

Concept developed by Eliyahu M. Goldratt as an application of his theory of constraints.

So far, none of the major project management software packages directly support critical chain planning and monitoring, although add-ons are available.

See also: project planning

Further reading

• Critical Chain, ISBN 0884271536
• Project Management In the Fast Lane, ISBN 1574441957
• Critical Chain Project Management, ISBN 1580530745

External links

• Getting Out From Between Parkinson's Rock and Murphy's Hard Place (Critical Chain basics for single projects)
• Program Management -- Turning Many Projects into Few Priorities with TOC (Multi-project management)
• Critical Chain and Risk Management - Protecting Project Value from Uncertainty
• Focused Performance weblog