- 1 - WILLIAMS, T.M., Eden, C.L., Ackermann, F.R., and Tait, A. (1995). Vicious circles of parallelism. International Journal of Project Management 13, 3, 151-155. The vicious circles of parallelism Terry Williams, Colin Eden, Fran Ackermann, Andrew Tait Department of Management Science, Strathclyde University, Glasgow Manufacturing development projects are frequently highly parallel and time- constrained. The authors undertook a study of such a project as part of a Delay and Disruption (D&D) litigation to show the effect of delays and in-development product enhancements. The use of the "cognitive mapping" technique revealed some key vicious circles, in particular increasing cross-relations between concurrent activities increases activity durations, which under time constraints causes activities to become more parallel and hence increase cross-relations. 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. The case study is used 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. INTRODUCTION The issues and difficulties involved in managing large engineering projects have been the subject of much study, and project management is now a science in its own right 1,2 . This is often quoted as starting with the Polaris program, which essentially saw the birth of a fully developed network analysis methodology (although Morris 3 argues that it was used as a smokescreen rather than as a planning method). The key to the network methodology is its description of which activities must be carried out serially, and which can be carried out in parallel. As the technology being developed by projects, and the economic environment within which projects are carried out, both develop, two trends can be seen, as described by Williams 4 - As the technology and thus the products become more complex and more intra- connected, the projects developing the products become more parallel, and it is proposed that these projects are more difficult to manage, and more likely to escalate. - Time-constraints on projects are becoming tighter, and time-based liquidated damages heavier, and it is proposed that this exacerbates the effect of the first trend. This paper discusses these two proposals in the light of a recent major litigation in which the authors were involved, describes some of the key vicious circles