The vicious circles of parallelism

Williams, Terence and Eden, Colin and Ackermann, Fran and Tait, Andrew (1995) The vicious circles of parallelism. International Journal of Project Management, 13 (3). pp. 151-155. ISSN 0263-7863 (

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Manufacturing development projects are frequently highly parallel and time-constrained. A study was undertaken of such a project as part of a delay and disruption (D&D) litigation to show the effects of delays and in-development product enhancements. The use of the cognitive-mapping technique revealed some key vicious circles, and in particular that increasing crossrelations between concurrent activities increases activity durations, which under time constraints causes activities to become more parallel and hence increases crossrelations. System dynamics was used to model these loops quantitatively, explaining the level of D&D experienced within the project, which was more than the sum of each individual causal effect as the effects compounded each other. A case study is used as a basis to analyse these effects, and discuss the wider implications for modelling projects for which project networks are the normal modelling medium, and possible ways in which the inadequacies of networks can be overcome.