Simulation-based approximation of the gain from applying overlapping activities

Schedule management is essential in construction projects to ensure successful completion. However, the dynamic nature of the construction industry introduces variability, leading to uncertainty and challenges in schedule implementation. This paper explores the use of schedule acceleration through overlapping activities as a solution to mitigate the impact of variability on project timelines. Risks associated with overlapping activities can lead to waste and offset anticipated schedule gains. To challenge the assumption that the schedule gain from activity overlapping is directly proportional to the amount of overlapping, a simulation model is developed and implemented in MATLAB where activities are modeled as beta-distributions. The model gradually increases the overlap percentage and evaluates the mean best-case, overall mean, and mean worst-case durations. An isolated overlap consisting of two activities is used to demonstrate the effect of overlapping. With a 1∶1 ratio between durations, it was found that, when using a 90% overlap, the loss in effect varied from 3.2% to 57.5% with an overall mean loss of 34.2%. These results emphasize that even in the most optimistic combination of distributions, the most likely duration still exceeds initial expectations, indicating the influence of variability on the schedule. Thus, the findings highlight the necessity of project managers to consider the impact of variability on overlapping activities, ensuring a more accurate schedule estimation. The study offers practical recommendations for project managers, including a diagram that advocates applying adjustment coefficients based on the degree of overlap and the ratio between the activity's durations. The diagram can be adopted in future scheduling to adjust durations when applying overlapping to minimize the risk of schedule delays.