Critical chain project management is a method of project management which was developed by Dr. Eliyahu M. Goldratt in 1997. It differs from the traditional methods of project methods as it aims to solve problems displayed by traditional project management methods such as longer than expected durations, frequently missed deadlines, increased costs in excess of budget, and substantially less deliverables than originally promised.
What were the problems with traditional project management?
The critical chain method is based on what is known as ‘The theory of constraints’. With this methodology, certain constraints are associated each task. These constraints are as follows:
Firstly, it is thought that when planning for a project, estimates for task durations are required and this causes unnecessary time to be spent on ensuring that estimates are correct. This additional safety time gives people a tendency to wait until the last moment to start a task and to delay the completion of the task. As a result, the safety which was included at the planning stage is wasted and, if any problems do occur, tasks over-run. In addition, the task durations are overestimated by the team members or task owners. This is typically done to add a safety margin to the task so as to be certain of its completion in the decided duration.
Another concern is that there is a certain amount of uncertainty in each task.
How does critical chain management aim to fix these constraints?
Critical chain project management uses safety ‘buffers’ to manage the impact of variation and uncertainty around projects. The safety at a task level is aggregated and moved to strategic points in the project flow. There are three types of buffer/strategic points necessary to ensure the project has sufficient safety:
The Project Buffer: This is the total pooled buffer which is inserted at the end of the project network between the last task and the completion date.
The Feeding Buffer: In a project network, there are path/s which feed into the critical path. The pooled buffer on each such path represents the feeding buffer to the critical path, resulting in providing some slack to the critical path. To protect against this, feeding buffers are inserted between the last task on a feeding path and the critical chain.
Resource Buffer- This is a virtual task inserted just before to critical chain tasks that require critical resources. This acts as an indicator for when the critical path is about to start. Resource buffers ensure that the appropriate people and skills are available to work on the Critical Chain tasks as soon as needed.
Overall, critical chain project management methods are very effective for organisations and they really help pave the way when it comes to project management practices which work.