Modeling concurrency tradeoffs and their effects on project duration and rework

Market pressures have forced many companies to increase concurrency in their work processes in order to shorten product delivery times. Unfortunately, there has been no reliable way to estimate the effects of increased concurrency on project duration or rework costs when overlapping interdependent activities. This research develops a new language and conceptual model to describe the effects of varying the degree of overlap between reciprocally interdependent activities in a design-manufacturing process. It builds on and extends extant models in the concurrent engineering literature. The conceptual framework classifies three main effects of concurrency: time overlap effect, early start penalty, and late start penalty. Further, this research shows that by changing the rate of evolution of design detail or the sensitivity of manufacturing to design changes, the effects of concurrency are modified. The three main effects of concurrency and the modifiers of those effects were incorporated into a computational model, FT-VDT. The model relates the completeness of upstream activity information to the probability of error in the downstream activity depending upon that upstream information as input, mediated by rates of evolution and sensitivity. The FT-VDT model was validated on three test cases—an idealized case study from the literature, and two real life projects in software development and construction. The results demonstrate the relationship between the degree of overlap of interdependent activities and both the probability of error and the amount of rework necessary to correct the error. The model results confirm, integrate, and extend results of prior research for the idealized case; and they are qualitatively consistent with empirical data from the two real life test cases. Finally, the results show that there is an optimal range of overlap that can reduce overall project duration. Overlap beyond that range results in increased overall project duration.