Critical Chain Project Management: Definition & Example

Instructor: Mike Miller
In this lesson you will learn what critical chain project management is, and how the project manager can use it in planning. We'll go over the six steps of execution, as well as the types of buffers used.

What Is Critical Chain Project Management?

Have you ever tried to run a project that just did not go as planned? Learn how to avoid some issues when it comes to scheduling.

Critical chain project management is a scheduling method that plans and manages projects with a focus on allowing for resource delay. Resources can include internal and external personnel (contractors or customers), physical space, logistics, and equipment.

Critical chain project management looks at the schedule and then includes resource availability to see how that will affect the activities and project completion. Think of walking on a road. You might be walking on it at a steady pace, but if your cement supplier is bringing cement to finish the road, you will be delayed. The resource caused the delay, not the task.

Dr. Eli Goldratt developed critical chain methodology in 1997 in his book Critical Chain. Dr. Goldratt developed this method due to numerous projects having issues with extended durations on activities, missed deliveries, and budget overruns.

When an activity's duration is overestimated there are tendencies for workers to fall into student syndrome (procrastinating), Parkinson's Law (spreading out the tasks to meet the time allotted) or cherry picking tasks. If the project falls into these traps, any buffer or cushions that were built in quickly disappear.

Steps in Critical Chain Development

There are six steps that a project manager who uses critical chain project management will have to follow. Let's say that Judy is a project manager planning a project.

1. Determine Aggressive Estimates

Judy always keeps her contracted delivery dates at the forefront of her mind. To help fight off procrastination or the effects of Parkinson's Law, the project manager will determine activity durations that are aggressive. Some recommend that the normal activity time allotted should be reduced by 50%, (though some consider that too aggressive and not obtainable).

2. Create the As Late As Possible Schedule

Judy will use scheduling software to create a schedule that works backwards from the completion date through each activity, each starting on the latest possible start date. This is in contrast to the standard practice of starting as early as possible. This tactic will install a sense of urgency in the project team and have them perform at the best of their abilities.

3. Determine the Critical Chain

Judy will determine which set of activities that, if delayed, will extend the end date of the project. She will determine this based off of resource availability. All tasks not in the critical chain are part of a feeding chain.

4. Decide Where Buffers Should Go

Here Judy will decide where buffers should be placed in the schedule. Buffers can be one of three types:

  • A project buffer is a single buffer added to the whole schedule, between the last activity and the ultimate deadline.
  • Feeder buffers are placed in between the last tasks from the feeding chain leading to critical chain activities.
  • Resource buffers are artificial buffers that make up for possible fluctuations in resource availability.

5. Determine Buffer Sizes

Here Judy will add appropriate buffer size (cushion) to activity durations. It is recommended that a cushion proportionate to the activity uncertainty or risk be included. This means that a more uncertain an activity is, the larger the buffer built in.

6. Add the Buffers to the Schedule

When Judy adds the buffers to the schedule, she creates a buffered schedule she can use to manage the critical chain project.

How to Use Critical Chain

Judy will begin to use the critical chain project management during the planning phase. She will investigate what personnel and resources are needed for the project by discussing with the managers the project's needs, including resources required.

She will make sure to include the buffers and cushions for duration. Not all resources will be available when needed or requested, so it's best to look for alternatives if an issue arises. For example, if the shop crane is unavailable during first shift, but free during second shift; Judy will see about using the crane during second shift.

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