Switches and crossings (S&Cs) are critical assets in the Swedish rail infrastructure, with a density of 0.8 S&C per track-km and renewal costs of up to 4.5 million SEK/S&C. The efficiency of maintenance strategies for S&Cs is vital from a (socio-)economic perspective.
The focus of this study is on the importance of the mix of maintenance activities performed on a S&C with respect to its life-cycle costs (LCCs). The study investigates the interdependencies between the deterioration mechanisms, preventive and corrective maintenance activities, and expected LCCs, including transportation costs due to traffic disruptions/delays.
One or a combination of different approaches are often used in the literature, such as engineering or LCC methods. In this research, a novel approach is introduced that combines mechanical simulations, data analysis, econometrics, and LCC calculations to compare the efficiency of different maintenance strategies.
The mechanical simulations consider one S&C on the Swedish railway network. The selection criteria were that the S&C is located on the main line, installed in 2014 (generates the longest observation period given the availability of data), and had no extreme values with respect traffic volume, maintenance activities and failures.
The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle–turnout interaction. Further, the relationship between frequency of preventive and occurrence of corrective maintenance activities is analyses using an econometric model. Implications of a specific mix of maintenance activities on the S&C lifetime and LCC are evaluated using different cost parameters.
Results obtained from mechanical simulations reveal the correlation between poor crossing geometry and higher rates of ballast settlement. The econometric analysis finds a statistically significant impact of (cumulative) preventive maintenance on corrective maintenance, i.e., more preventive maintenance leads to fewer corrective activities.
Based on a standard mix of maintenance activities (inferred using econometric regression across all S&Cs), the lifetime of the selected S&C is estimated to 10 years with a lower associated LCC than that resulting from the record of performed maintenance activities at the site. The LCC evaluations highlight the potential to improve the efficiency of S&C maintenance by adopting proactive strategies.