The Critical Chain Method (CCM) is used to perform Schedule Network Analysis that considers task dependencies, limited resource availability, and buffers.  It’s used to prepare the project schedule when limited or restricted resources are available.

In this method, the Program Manager (PM) usually schedules all or most high-risk or critical activities in the earlier stage of the project schedule. This allows the critical tasks to be completed early and gives buffers to handle unexpected problems if they arise. Also, the PM will combine several tasks into one task and assign one resource to handle all.

Critical Chain Method (CCM) Goal

The Critical Chain Method (CCM) aims to eliminate project schedule delays due to uncertainties, overestimating task duration, and wasted internal buffers.

Utilizing the Critical Chain Method (CCM) in Your Schedule

To develop a project schedule using the critical chain method you do the following:

• Define Activities: What needs to be done to finish the project?
• Estimate task durations: How long does each task take to finish?
• Calculate Buffer: Make plans for what could go wrong based on who is doing the work and how much time they have to spend on the project.

Critical Chain Method (CCM) Development Steps

The six (6) steps involved in the development of the CCM are:

1. Identify all activities and dependencies
2. Construct a Schedule Network Diagram
3. Define constraints
4. Determine critical path
5. Determine buffers
6. Apply resource availability

Critical Chain Method (CCM) Buffers

A Buffer is extra time added to a plan/schedule so that a task can be done and delays can be considered. The CCM has three (3) different types of Buffers, which are:

1. Resource buffer: is inserted just before a critical chain activity where a critical resource is required. It’s used to remind the project team that a resource is needed and to finish up prior activities.
2. Feeding buffer: is inserted as a safety margin in the non-critical chain of a network schedule. It’s placed where the path feeds back into the critical chain path.
3. Project buffer: the summation of all the internal buffers added to each project task or activity.

Difference Between Critical Chain Method (CCM) and Critical Path Method (CPM)

There are a few differences between the critical chain and the critical path methods, but they both focus on schedule development and estimation. These are:

• Critical Path Method is focused on how long a project is based on task estimation and the amount of float on a project.
• Critical Chain Method operates on shortening how long a project is due to overestimation, uncertainties, and buffers.

Benefits of the Critical Chain Method (CCM)

The critical chain method is more effective than the critical path method in several important ways. Among these ways are:

• The critical chain method gives all of a project’s resources to it. So, if a task is done early, you can move on to the next one without hitting any snags.
• The project manager is in charge of managing the buffer, not the team. It is up to the team to finish their tasks within the estimated time frame.

AcqLinks and References:

• [1] Defense Systems Management College “Scheduling Guide for Program Managers” – Oct 2001
• DoD “Integrated Master Plan and Integrated Master Schedule Preparation and User Guide” – 21 Oct 2005
• CDC “Project Scheduling Best Practices/Guide” – 30 Jun 2007
• GAO 12-120G “Schedule Assessment Guide: Best Practices for Project Schedule” – May 2012

Updated: 11/24/2022

Rank: G1.2