Similarities
Both critical path and critical chain project management are techniques for planning and managing projects. They both focus on identifying the activities that are essential for completing the project on time and within budget.
Differences
The main difference between the two approaches lies in how they handle the uncertainty and variability inherent in project execution:
- Critical Path Method (CPM): CPM assumes that activities will be completed as planned. It focuses on the longest sequence of activities, known as the critical path, and assumes that any delay in these activities will delay the entire project.
- Critical Chain Project Management (CCPM): CCPM acknowledges that delays are inevitable and uses buffers to account for them. It focuses on the critical chain, which is the longest sequence of activities considering resource constraints and dependencies.
Key Differences in Detail:
- Focus: CPM focuses on the critical path, while CCPM focuses on the critical chain, which is the longest sequence of activities considering resource constraints and dependencies.
- Buffering: CPM does not explicitly incorporate buffers, while CCPM uses buffers (project buffer, feeding buffers, and resource buffers) to account for potential delays.
- Resource Allocation: CPM doesn't explicitly address resource allocation, while CCPM considers resource availability and limitations when defining the critical chain.
- Project Completion Time: CPM often underestimates project completion time due to ignoring potential delays, while CCPM aims to improve project completion time by incorporating buffers and addressing resource constraints.
Example
Imagine a project with two tasks:
- Task A: Writing a report (5 days)
- Task B: Designing a presentation (3 days)
CPM: The critical path would be Task A, as it takes longer. CPM assumes Task A will take exactly 5 days.
CCPM: CCPM would consider the available resources and potential delays. If the writer is also needed for other tasks, CCPM would add a buffer to Task A to account for potential delays caused by resource allocation.
Practical Insights
- CCPM is more realistic: It acknowledges the inevitable delays in projects and provides a framework for managing them.
- CCPM is more efficient: By using buffers and optimizing resource allocation, CCPM can improve project completion time and reduce overall project risk.
