On the merits and pitfalls of critical chain scheduling

The direct application of the Theory of Constraints (TOC) to project management, known as Critical Chain Scheduling and Buffer Management (CC/BM), has recently emerged as one of the most popular approaches to project management. It is the objective of this paper to highlight the merits and pitfalls of the CC/BM scheduling approach. Following a short overview of the fundamentals of CC/BM, the strengths and weaknesses of the approach are put into perspective, based on a critical analysis of the literature as well as our own experimentation with commercial CC/BM software. The CC/BM scheduling mechanism is tested in a full factorial experiment performed on a set of benchmark problems. It appears that the 50% rule for buffer sizing may lead to a serious over-estimation of the required buffer protection. Regularly updating the baseline schedule and the critical chain provides the best intermediate estimates of the final project duration and yields the smallest final project duration. Using clever project scheduling and rescheduling mechanisms such as branch-and-bound, has a beneficiary effect on the final makespan.