A comparison of fuzzy indices with Monte Carlo simulations for risk assessment at the preliminary stages of transit project planning

Scope and method of study. The purpose of this study was to find and apply the most favorable technique to introduce and evaluate the uncertainty of risk that environmental factors have on transit projects during the preliminary phase of planning.; Findings and conclusions. The fuzzy approach was shown in this research application to deliver comparable results as the Monte Carlo simulations. The fuzzy results are more efficient in depicting variation of uncertainty inherent to an early stage of a project. Monte Carlo analysis provided a better statistical characterization of the results, however, such detailed information is not necessary at the pre-planning stage. It also requires more input data, which are usually not available at this point of the project. Moreover, Monte Carlo analysis includes time consuming performance of simulations. An uncertainty analysis based upon Monte Carlo simulation would limit a future user to only the default simulation, rather than having the flexibility ensured by fuzzy approach to configure a simulation accordingly to project conditions. The fuzzy approach, applied to the BART San Francisco Airport Extension project, was found to be a suitable and efficient technique for risk assessment in the early stage of project. It supplied valuable information on the uncertainty associated with the project risk in an easy and time effective manner. (Abstract shortened by UMI.)...