On the nature of discontinuities in system dynamics modelling of disrupted projects

When complex projects result in large-cost over-runs, managers want to understand why this happened. There may be the possibility of making a claim against another party, or managers may simply wish to learn from any mistakes made. When using system dynamics (SD) models to analyse the reasons for project over-runs as a part of a litigation or organizational learning process, there is a strong focus on explaining historical aspects precisely. This leads to a need for the inclusion of discontinuous variables. This paper discusses the nature of discontinuities in SD models of project over-runs. Examples are given to demonstrate that the modelling of such discontinuities needs to be an integral part of the continuous simulation modelling process. Their inclusion helps to improve model validity and also, by forcing validity, uncover the important drivers of project behaviour. The examples given in this paper are significant drivers and suggest important learning about the behaviour of disrupted complex projects.