Yvonne Moret

Transportation construction projects are often plagued by cost overruns and delays. Applying contingencies and estimating risks at the project level often do not capture the multiple uncertainties in the construction process of large transportation projects. Thus, there is a need for innovative approaches and tools to avoid large construction cost and duration overruns. To counteract such underestimations, a construction model and an uncertainty model are developed. In the construction model, the construction of the four main types of structures in rail lines (tunnels, viaducts, cuts, and embankments) is modeled bottom-up from the single activity to the entire rail line. In the uncertainty model, three sources of uncertainty (variability in the construction process, correlations between the costs of repeated activities, and disruptive events) are modeled jointly at the level of the single activity. In a Monte Carlo simulation environment, these uncertainties are propagated to the total constructio...

The total construction cost and time of projects are often overrun. It is known that when positive correlations between costs are disregarded, the range of possible total construction costs is underestimated. A model is needed to estimate the effect of correlations on the probability distributions of total cost and total time. Four cost–cost and one cost–time correlations in the construction of rail lines were identified, two of which were investigated in detail using a model applicable to the construction of any networked system. This paper presents the theoretical background of the model, the correlations occurring in rail line construction, and the analysis of the impact of such correlations in two case studies including several scenarios and one sensitivity analysis. The results clearly show that the standard deviation of the total cost increases with the magnitude of the correlation and, most importantly, it dramatically increases with the number of costs that are correlated; it also depends ...

To counteract cost escalation and delays in infrastructure construction, an estimation model has been developed that simulates project uncertainty with probability distributions, correlations, and disruptive events. When applied to a new rail line project, three model inputs were not available from the designers: time distributions, cost correlations, and probability of occurrence and cost/time impacts of disruptive events. Experts in the field of tunnel-, viaduct-, and earthwork construction were asked to estimate the unavailable information. This paper presents a brief overview of biases that occur when experts estimate probabilities, the calibration steps taken to prevent the experts from being affected by such biases, and example questions from the questionnaire, followed by an in-depth discussion of findings. Unexpectedly, the experts followed radically different estimation techniques: the tunnel expert recalled values from past projects, the viaduct expert calculated the required values, whi...