How Critical Chain Extends Critical Path

Critical Chain assumes a good critical path network that has been effectively resource leveled. Starting from that point, Critical Chain enhances the ability to optimize the schedule and sets the stage for improved project monitoring and control. It should be noted that some of the actions needed to implement Critical Chain successfully might be significant changes for an organization. Following are specific ways that the Critical Chain approach works and adds value.

1. Using the Critical Chain approach, team members are asked to dedicate themselves to a project task, to complete it as quickly as possible, and to periodically report how many days are remaining. When planning a project, task times should be estimated much closer to how long the task will take with dedicated resources, rather than elapsed times assuming the organization's current practice of assign ing resources to work on several tasks at once. This also significantly reduces behaviors called "Student Syndrome" and "Parkinson's Law."

2. Bad multitasking is significantly reduced, permanently. This goes hand in hand with reducing task estimates to dedicated elapsed times and having people complete tasks before starting new ones.

3. In executing a project, people are not measured and are not held accountable for completing their tasks on time. People are asked to pass on their outputs to the next resource as quickly as possible. Use of intermediate due dates is limited. This is sometimes called the "relay runner ethic."

4. By taking resource dependency and logical task dependency into account, the longest sequence of dependent tasks can be seen more clearly. This longest sequence, the Critical Chain, may cross logical paths in the network.

5. Buffers are a key part of the schedule and how it is managed. The ability to increase the certainty of project completion dates is closely related to the use of buffers. The use of buffers, strategically placed in the plan, allows the planner to clearly accommodate all common cause variations (variations in duration that predictably occur because they are part of the system within which projects are performed). Buffer types include project buffers, feeding buffers, resource buffers, drum buffers, and strategic resource buffers.

6. Critical Path uses a concept of slack time or float to determine how much flexibility there is in noncritical path tasks. Critical Chain approach assumes that slack times often do not provide real flexibility due to behaviors such as "Student Syndrome." Critical Chain approach groups tasks on each noncritical (or feeding) path entering into the Critical Chain and "protects" the Critical Chain with a feeding buffer. The feeding buffer is equivalent to a schedule contingency reserve that is local to a part of the project. The Critical Chain approach is explicit and systematic about the use of feeding buffers throughout the task network.

7. This buffering allows for noncritical tasks to be scheduled at their latest possible start times to discourage costly early investment of work in process. This also significantly reduces behaviors called "Student Syndrome" and "Parkinson's Law." Early starts are discouraged unless there is a major strategic reason for doing so.

8. Often, the Critical Path changes during execution because there is no buffer to absorb the variation in task times. If implemented correctly, the Critical Chain plan and the Critical Chain itself do not change throughout the life of the project because the buffers absorb the uncertainties in task duration.

9. Critical Chain recognizes that there are multiproject environments in which projects have resource-based interdependencies. In other words, projects share a common resource pool for at least some tasks.

10. The Critical Chain approach identifies the critical resource (called a drum resource) across a collection of projects. When overloaded or not available, this resource is the one most likely to impact the project cycle time of all projects.

11. The staggered introduction of projects into the system is used to improve the flow of projects, to increase the predictability in each project outcome, and to increase the effectiveness of critical resources by minimizing the effect of bad multitasking.

A shorter project cycle time and an increase of the number of projects that can be pushed through the system without increasing resources result from staggering the release of new projects.

12. Similar to vertical traceability in Critical Path, the Critical Chain plan and detailed schedules are linked entities. Any logic at the detailed levels must be reflected in the summary level(s).

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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