Life cycle cost analysis of the ventilation system in Stockholm's road tunnels

Purpose The purpose of this paper is to develop a practical economic replacement decision model to identify the economic lifetime of the ventilation system used by Trafikverket in its Stockholm tunnels. Design/methodology/approach The proposed data-driven optimisation model considers operating and maintenance costs, purchase price and system resale value for a ventilation system consisting of 121 fans. The study identified data quality problems in Trafikverket's MAXIMO database. Findings It is found that the absolute economic replacement time (ERT) of the ventilation system is 108 months but for a range of 100-120 months, the total cost remains almost constant. Sensitivity and regression analysis showed that the operating cost has the largest impact on the ERT. Originality/value The results are promising; the company has the possibility of significantly reducing the LCC of the ventilation system by optimising its lifetime. In addition, the proposed model can be used for other systems with repairable components, making it applicable, useful and implementable within Trafikverket more generally.