Buffer Sizing Methods to Compare Critical Chain Project Management with Critical Path

Introduction

Creation of reliable and accurate schedules in project management is the first step towards project success (Santiago and Magallon, 2009; Kelley, 1963). Using the Critical Path Method (CPM) implies calculating Early Start and Finish dates as well as Late Start and Finish dates by forward and backward analysis of the project network diagram paths. Choosing the relevant resources is usually done after identifying the path. Activity owners add buffers (i.e. safety margin) for each activity in order to overcome the uncertainties (Leach, 2014). Using CPM, if a resource completes an activity before the planned finish date, the time gain is still not propagated to next activity. That is because the early start date of next activity has been not reached yet. However, delays are propagated which may even change the existing critical path (Herroelen, 2001). Critical chain project management (CCPM) is the direct application of the theory of constraints to project management developed by Goldrate (1990; 1997;1998) which is a technique related to scheduling analysis for network that considers task dependencies, scarcity of resources, and buffers.