Factors That Influence the Concession Period Length for Tunnel Projects under BOT Contracts

This article investigates the factors and corresponding subfactors affecting the length of the concession period for a build-operate-transfer (BOT) tunnel project. It includes five steps, namely, identifying the influential factors of concession period length determination, identifying the subinfluential factors, quantification of the factors, variable ranking, and variable testing. The influential factors and subfactors were identified through an extensive review of literature and a questionnaire survey. Qualitative factors were then quantified and all the factors were scaled and ranked by the entropy method, and finally tested by a support vector machine-based prediction model. In the end, a set of key influential factors of concession period length was developed. It is expected that the developed factors can improve the accuracy and effectiveness of concession period length determination.