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. Two alternative methodologies were considered: Monte Carlo analysis and fuzzy approach. Both techniques were found to deliver comparable results. 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, it requires more input data, which are usually not available at this point of the project. Fuzzy approach ensured the future user flexibility 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 a project.