Incorporation of resource reliability into critical chain project management buffer sizing

The methods presently used for buffer sizing of Critical Chain Project Management (CCPM) have lagged far behind capturing the stochastic nature of resource acquisition in real-world projects. The work described herein represents a new step towards the sizing of buffers for CCPM by developing a probabilistic measure obtained through a reliability analysis of project resources. The proposed method treats the resource availability as a random variable in project scheduling, meaning that each resource has a distribution of possible values of availability. In this method, buffer size is determined by assigning a scaling factor to the standard deviation of a chain. This scaling factor is the function of the reliability of available resources assigned to the chain activities, taking into account the likelihood of timely completion of the chain given the reliability of each individual resource. Sensitivity analysis, as well as the comparison of the proposed method with the conventional buffer sizing methods, reveal the effectiveness of the new method.