PSI - Issue 84

D. Di Fiore et al. / Procedia Structural Integrity 84 (2026) 159–166

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3.2. Duration and social costs In addition to the direct costs of capital expenditure (CapEx) and operating expenditure (OpEx), there are also indirect costs resulting from time lost by vehicles in queues. These are estimated at €25 per hour for light vehicles and €33 per hour for heavy vehicles. These values are taken from sector guidelines. In particular, the cost for light vehicles was calculated by taking into account the average vehicle occupancy rate (1.7 passengers per vehicle) and the unit cost of €14.72 per hour (€14.72 x 1.7 = €25 per hour). The number of hours lost in queues is assessed using simplified transport analyses based on the assumption of traffic diversion to the opposite carriageway, without considering possible re-routing (i.e. users do not abandon their journey or use alternative routes). The data required for the analysis are the average number of vehicles per day and the distribution of light and heavy vehicles. These data are used in a combination matrix to calculate the total number of hours vehicles spend in queues. This matrix was constructed using a traffic model calibrated on a motorway section that is similar in terms of the number of lanes and traffic to that experienced on an average day in October 2022. 3.3. Carbon footprint of the solutions The Carbon Footprint (CFP) is defined as the sum of greenhouse gas emissions and removals associated with a product system, expressed in CO₂ equivalents and based on a Life Cycle Assessment (LCA). The LCA follows an ISO-standardized methodology comprising goal and scope definition, inventory analysis, impact assessment, and interpretation, which are iteratively linked. A cradle-to-gate system boundary was adopted, including raw material supply, material production, transport, and installation, while excluding use and end-of-life phases due to the assumption of extended service life through maintenance. The CFP was estimated at the design stage using the bill of quantities and calculated with certified emission factors based on the IPCC 2013 v1.3 method implemented in SimaPro and compliant with EN 15804. The resulting CFP values for the construction phase are 809, 4’320, and 7’ 420 kg CO₂ eq per meter for IMS, IRS, and TRS, respectively. 4. Findings The results of a specific tunnel analysis are presented here, along with insights into the main differences between the analysis of non-repetition of treatments and the comprehensive life cycle assessment of costs.

Fig. 7. Discounted CapEx when treatments are not repeated (left side) and vice versa (right side)

In Fig. 7 and 8 capital and operative expenditures are evaluated at mid (2038) and long term (2075). Clearly, the lower the CapEx, the higher the future OpEx, but, without considering the possibility of repeating some treatments in the future, cost estimates are unreliable, particularly for less invasive strategies such as IMS and, eventually, IRS, which are cheaper but more prone to deterioration. Taking repetition or extraordinary maintenance into consideration