This case study is presented after observations were made that partially contrast the prevailing picture of railway curve squeal given in the literature. These are observations with significance both for modelling and condition monitoring. The current case study will be followed by a subsequent investigation focused on the validation and application of a simulation model to investigate root-causes for curve squeal at the Stockholm metro. Curve squeal in a 213 m radius curve on the Stockholm metro is studied. Data includes track characteristics (rail profile, rail roughness and gauge width) and noise measured at the trackside as well as by two vehicles equipped with an on-board mounted noise monitoring system. The current case study contrasts field measurements of curve squeal reported in the literature by a relative shift of emitted noise towards higher frequencies. Wayside noise measurements in the studied curve during a few hours showed squeal generation for all vehicle passages with dominating 1/3 octave band centre frequencies in the range between 6.3–15.8  kHz. Noise data measured during one year of regular traffic of two vehicles equipped with a monitoring system were obtained. The occurrence of curve squeal was analysed through an implementation of the curve squeal detection algorithm in operation at the Stockholm metro. This algorithm was also applied to search for events of squeal noise radiation from the outer wheel. Results show emissions of squeal noise from the inner and outer wheel for 65 % and 8 % of the vehicle passages through the studied curve, respectively. Further, the occurrence of curve squeal radiated from the inner wheel was found to increase by 10 % after rail grinding. In the literature, squeal radiated from the outer wheel is described as having an intermittent character with magnified spectral components in the frequency range between 5–10  kHz. In contrast, the current work presents sustained tonal squeal generated from the outer wheel with similar noise characteristics as typically related to ordinary curve squeal. 

This study investigates eight crossings on the Western Main Line in Sweden to evaluate traditional manual geometry assessments using templates, and to compare them with condition indicators derived from sleeper-mounted accelerometers. High-resolution 3D scans of the crossing rails were used to virtually replicate the template inspection procedure defined by the Swedish Transport Administration. These scans also served as input for simulations of wheel–rail kinematics and dynamic vehicle–track interaction, enabling extraction of condition indicators for comparison, including sleeper acceleration and velocity metrics, as well as a wheel–rail kinematic parameter referred to as the dip angle. All indicators were evaluated based on their correlation with the maximum vertical wheel–rail contact force at the transition between the crossing nose and wing rail. The results show that template-based wear measures lack predictive capacity for generated impact forces, which raises the question of the use of these as condition indicators in a predictive maintenance context. Sleeper responses show stronger potential, and the dip angle shows high correlation as expected. This work provides insight into the critical role of crossing geometry, highlights limitations of current maintenance practices, and forms a basis for the development of continuous monitoring strategies for improved maintenance planning that better manage long-term mechanical deterioration.

Track irregularities induce increased wheel-rail contact forces causing poor ride comfort, accelerated mechanical degradation of vehicle and track or even failures that may lead to speed restrictions or temporary track closure. Today's monitoring of railway tracks in Sweden using measurement vehicles consumes traffic capacity and means a restriction in data collection to a few occasions per year. Remote sensing such as Interferometric Synthetic Aperture Radar (InSAR) can be used to monitor ground deformation in the close vicinity of the track with potential impact on the track substructure. The importance of geotechnical properties of the track substructure on the development of track irregularities is well known from experience and literature and is demonstrated for example by the re-development of discrete track irregularities at the same locations after tamping. The Sentinel 1A and 1B satellites have collected data every 12th day resulting in roughly weekly observations between 2016 and 2021. This case study evaluates the relationship between ground deformation in the ascending and descending tracks, basic geological properties and track irregularity. The average negative ground movement rate measured using InSAR was higher for track segments that had experienced poor track geometry in the ascending path, especially for track built on clay, moraine or glaciofuvial deposits. A higher variance in ground motion was found in both the ascending and descending path near segments which had experienced track geometry alerts. Future work should further investigate these relationships by observing vertical and horizontal movement separately, incorporating a temporal dimension, and increasing spatial resolution, taking special consideration to variation of settlement surrounding and along the track.

The work outlines a coupled multibody simulation (MBS) and life-cycle cost (LCC) analysis framework to assess resource-efficient railway maintenance strategies based on look-up tables. Iterative MBSs are used to predict long-term wear and rolling contact fatigue for two standard elements of the Swedish iron-ore line. Maintenance strategies are optimized in a socio-economic assessment including costs associated with e.g. interventions, capacity possession and CO2 emissions. Results find joint renewal of both rails reduces LCC by 26% compared to separate replacement. Ongoing work extends MBS to multiyear traffic and assessment of additional standard-elements to enable LCC optimization at railway line level.

Spårväxeln är en kritisk nod som samtidigt med erbjudandet om flexibilitet även introducerar störningskänslighet i järnvägssystemet. Den orsakar kostnader för infrastrukturförvaltaren genom ett högre underhållsbehov jämfört med vanligt spår och för operatörer, passagerare och godsägare genom de kostnader som förseningar medför. En tidigare studie om spårväxlar visar att fel i korsningsrälen hör till felen med störst påverkan på trafiken. Korsningsrälen är extra utsatt för mekanisk nedbrytning på grund av diskontinuiteten i farbanan som övergången mellan vingräl och korsningsnos medför. Slipning och reperationssvetsning (påsvetsning) är de två vanligaste livstidsförlängande underhållsåtgärderna där den senare kan krävas vid svårare fel. Båda metodernas utfall är i hög grad beroende av utförarens expertis, men reperationssvetsning riskerar även att påverka materialsammansättning negativt. För att bättre förstå nedbrytningsmekanismer, felkällor och genomförda underhållsåtgärder analyserar denna studie historiska data från infrastruktur och besiktningsanmärkningar.

Railway track degradation is a complex process influenced by various damage mechanisms, including rolling contact fatigue (RCF), wear, and track geometry degradation due to settlement and gauge widening. These interrelated mechanisms require coordinated maintenance interventions to prevent costly failures and maintain operations in the railway system. Focusing on the case of a small radius curve on Sweden's Iron-ore line, the study illustrates the approach on a critical track section that experiences significant wear due to heavy traffic loads. Different scenarios are studied, including varying axle loads (30 and 32.5 tons) and rail profiles (MB5 and MB6), to simulate the track's degradation over time.

Findings from the study reveal that the approach can be used to find optimal strategies for track maintenance which minimize LCCs while extending the lifetime of railway assets. The results highlight the impacts of the timing and frequency of maintenance interventions on both the asset condition and the LCCs. Sensitivity analyses further illustrate that factors such as the rate of track gauge widening, maintenance costs, and renewal costs are important in determining the optimal maintenance strategy. Thus, adjusting maintenance frequencies based on these factors can allow for a more adapted and cost-effective approach to track and asset management in railway infrastructure.

This work concludes that combining mechanical simulations, maintenance look-up tables, and LCC modelling can provide a new robust approach for optimizing railway maintenance strategies. This approach can help IMs with insights into the long-term implications of various maintenance interventions, allowing for more informed and strategic railway infrastructure management. Future research should explore the application of this methodology to other critical railway components, e.g., switches and crossings, and consider more dynamic models including variations in rolling stock and environmental conditions. Additionally, refining cost parameters, particularly renewal and capacity costs, can further enhance the accuracy of the results, and the effectiveness of the adopted maintenance strategies.

A computationally efficient approach, that uses pre-calculated simulation-based look-up tables of long-term track degradation to evaluate and optimise maintenance strategies, is proposed. The methodology combines iterative multibody simulations – to model the evolution of rail profiles and the distribution of rolling-contact fatigue under realistic conditions – and an optimisation procedure aimed at minimising the lifecycle costs. The research explores the interplay between long-term track degradation, maintenance interventions, and lifecycle costs. The approach is illustrated through an application to a small radius curve on Sweden’s Iron-ore line, focusing on rail grinding and track gauge correction. Optimal renewal and maintenance strategies are analysed for different scenarios such as rail profiles and axle loads. The results highlight the importance of gauge widening rates, rail profiles and axle loads in track deterioration as well as their effects on the asset’s lifecycle costs. A sensitivity analysis is conducted to study the impact of different parameters such as maintenance and renewal costs, and gauge widening rates. The proposed approach offers infrastructure managers a systematic method for efficient planning of maintenance interventions on various assets. Future work could explore applications to larger infrastructure areas, encompassing multiple assets with a complex composition of tangent and curved track sections as well as switches & crossings. 

Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time, this makes them critical since they can cause costly delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both the life-cycle costs (LCCs) of the assets and socio-economic transportation costs for passengers and freight customers. In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) for the crossing panel – an S&C subsystem – is investigated using a combination of mechanical and econometric modelling. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle– turnout interaction. Long-term mechanical degradation of the crossing panel is simulated for different maintenance strategies that correspond to different timing of the associated maintenance measures (crossing repair welding and tamping). This provides the basis for analysing the interdependence between preventive and corrective activities using econometric modelling. Based on a case study of a common type of S&Cs in the Swedish infrastructure, the impact of different maintenance strategies on LCC and transportation costs is analysed. Opportunities and challenges in the development of more economically effective maintenance strategies of S&Cs are discussed. 

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.  

Rail transport is expected to become a key component in the development of a long-term sustainable transport system. The planning, construction, operation, and maintenance of railway infrastructure are crucial in this effort. Hence, it is essential to ascertain that the railway infrastructure withstands and is adapted to extreme weather conditions and climate change. This study focuses on evaluating climate adaptation measures for lateral track buckling in Sweden. Through a literature review and interview with an expert at Swedish Transport Administration, it is highlighted that the maintenance status of railway infrastructure plays a significant role in the occurrence of lateral track buckling. According to the expert, inadequate track maintenance is the primary cause of lateral track buckling rather than weather variables like air temperature. The interview also clarifies that the chain of events related to the handling of track buckling is mainly initiated by the observation of a discrete lateral irregularity by a train driver, whereupon the train dispatcher at the traffic management center stops traffic until the location in the track has been inspected by a track entrepreneur. During the inspection, up to half of the observed cases of track buckling turn out to be false.