Exploring the true cost of infrastructure transit projects: Road vs Tunnel alternatives

Transport infrastructure plays a significant role in economic development and social connectivity. Decisions regarding transport projects are made at several stages including, planning, prioritizing, funding, and implementation. Accurate and structured evaluation of infrastructure alternatives is essential for effective decision-making and proper resource allocation. This paper addresses the need for a holistic and comprehensive assessment by employing Cost-Benefit Analysis (CBA) and Life Cycle Costing Analysis (LCCA) to evaluate various project alternatives. The methodology deployed incorporates the evaluation of construction, operation, and maintenance costs, as well as the benefits derived taking into consideration financial and economic aspects. By implementing a comparative analysis between the surface road to road tunnels in terms of their equivalent length the analysis establishes a ratio, Tunnel-to-Road Equivalent Length ratio (TREL ratio), of these two infrastructure options as a function of Annual Average Daily Traffic (AADT) and geotechnical conditions using the Geotechnical Strength Index (GSI) rock mass categorization. The Greece case has been utilized as the case study to demonstrate the applicability of the proposed methodology. The sensitivity analysis shows that AADT has a greater influence on the efficiency of such projects than the geotechnical conditions, which have been typically perceived as one of the most critical factors. The results and methodology presented offer a basis for determining a composite assessment of easy-to-use, yet coherent indices under which surface roads and tunnel projects can be benchmarked. Furtherly, it provides valuable insights for initial project assessments and decision-making processes.