Iowa State University - Home Extension and Outreach - Home ISUE Logo
CIRAS - Iowa State University - Extension and Outreach

CIRAS - TOC - Applications

Critical Chain Project Management

Contact us

A project’s success is measured by meeting the original commitments for scope, due date, and budget. Since the project environment has a high level of inherent uncertainty, projects rarely satisfy all three of the basic commitments. Project managers are forced to sacrifice some commitment(s) in order to meet other commitment(s). In a multi-project management environment, this conflict puts the success of all projects in the organization at risk.

Traditional project management methods account for the presence of this inherent variation through individual task and project estimates that are padded with safety. A project manager’s job then consists of making decisions and taking actions based on the finish date of each task and how it affects the overall project schedule. This practice makes projects extremely difficult, if not impossible, to manage and control.

Critical Chain Project Management (CCPM) acknowledges that a large part of the variation existing in projects cannot be eliminated. It improves the accuracy of prediction for project plans by addressing variation on a system level through the use of project buffers and feeding buffers. These strategically placed buffers aggregate the protection the project needs to meet its commitments and help focus the project manager’s efforts. The duration of a project buffer is derived from the tasks in the Critical Chain and the buffer is placed at the end of the project. Feeding buffers are placed at the end of a chain of dependent tasks feeding into the Critical Chain and their durations are derived from the tasks in that chain.

The Critical Chain of a project is defined as the longest chain of dependent events and takes into account both task dependencies and resource conflicts. It is also the constraint of an individual project. For the multi-project organization as a whole, the constraint is the capacity constrained resource, or that resource where a large improvement in local performance will lead to the largest improvement in overall system performance.

Multi-tasking is another common practice that may be keeping a project management system from reaching its goal. CCPM calls for the elimination of bad multi-tasking through the prioritization of projects and tasks for individual resources, particularly the capacity constrained resource.

For more information contact Jeff Mohr, or consult the following resources:

  • "Critical Chain" by Goldratt
  • "Critical Chain Project Management" by Leach
  • "Project Management in the Fast Lane" by Newbold


Critical Chain Project Management Diagram.