Factors of schedule and cost performance of tunnel construction megaprojects

Aims: This study illustrates the main factors that influence the cost overruns and schedule delays of tunnel construction megaprojects. Objective: An empirical analysis was carried out based on a dataset collected from a number of recent tunnel megaprojects worldwide. Methods: Analyses of variances and regression analyses were conducted to infer statistical significance and understand the relationships that exist between cost overruns, time delays and variables of context, technical, and governance characteristics of the sample projects. Results: The most significant factors are those related to the complexity of infrastructure and the type of contracting system used to deliver the project. In particular, some technical characteristics pertinent to the size of the tunnel reveal to be influencing factors of both schedule delay and cost overrun, while the usage of a traditional contracting mechanism is likely to impact the cost overrun. The type of infrastructure, region, ownership, and funding scheme are not found to be statistically significant determinants of cost and time performance. Conclusion: This analysis reaffirms that the size and complexity are important factors of typical low performance of tunnel construction megaprojects. The results of this study can be used for strategic design and planning by decision-makers, project managers and designers.