Editorial for the Special Issue of Vibration: Railway Dynamics and Ground-Borne Vibrations

Rapid urbanisation, the demand for efficient mobility, and the need to mitigate climate change are among the major societal challenges of our time. These challenges have driven the extensive expansion of railway infrastructure in modern cities, raising environmental concerns about the generation and propagation of vibrations and noise, which can adversely affect the comfort, well-being, and quality of life of people living and working in the vicinity of railway lines. In parallel, the increasing demands placed on railway systems, including higher speeds, traffic density, and enhanced operational reliability, have intensified the need for a deeper understanding of railway dynamics and the mechanisms governing the generation, transmission, and mitigation of vibrations.

Addressing these challenges requires multidisciplinary approaches encompassing vehicle-track interaction, wave propagation in soils, structural dynamics, vibration control technologies, and monitoring systems. The Special Issue brings together nine contributions covering a broad spectrum of topics, ranging from fundamental studies of railway dynamic behaviour to practical solutions for vibration and noise prediction, mitigation, and monitoring.

Colaço et al. [Contribution 1] provide a comprehensive review of railway-induced ground-borne vibrations, discussing the mechanisms of vibration generation and propagation, current prediction methodologies, available mitigation measures, and emerging research directions. The authors highlight that harmonised international regulations governing railway-induced vibration remain lacking, and that uncertainty in the prediction procedure remains relatively high. Furthermore, regarding mitigation, although a variety of solutions exist, their effectiveness depends strongly on local conditions and system characteristics. Therefore, mitigation measures should be designed on a site-specific basis.

Valuable insights into the physical mechanisms governing vibration propagation from railway sources through the soil and into adjacent structures, contributing to the validation and improvement of prediction models, can be found in Auersch et al. [Contribution 2]. This work combines field measurements, analytical interpretation, and predictive modelling to investigate the excitation and transmission of train-induced ground and building vibrations.

Tao et al. [Contribution 3] propose a hybrid modelling framework for predicting ground-borne vibrations in metro depots that integrates train dynamics, soil response, pile foundations, and structural interaction. By combining numerical simulations, analytical impedance models, and measurement data, the proposed framework offers a promising approach to addressing the uncertainties inherent in current prediction procedures.

Several contributions focus on vibration and noise mitigation strategies. Sadeghi et al. [Contribution 4] assess the effectiveness of dynamic vibration absorbers for reducing metro-induced ground vibrations, demonstrating their potential as a practical and efficient mitigation measure. Gu et al. [Contribution 5] investigate how rail track design can be optimised to mitigate vibrations transmitted to buildings directly above a double-deck railway depot, providing practical guidance on track configuration and vibration-isolation solutions. Li et al. [Contribution 6] studied the aerodynamic behaviour of a semi-enclosed sound barrier located in a high-speed railway bridge, contributing to the understanding and design of noise mitigation systems in complex railway geometries. Collectively, these studies emphasise that effective mitigation strategies must be tailored to specific operational and site conditions.

The dynamic behaviour of railway vehicles and infrastructure is also addressed. Dimitrovová [Contribution 7] investigates the potential instability of a moving bogie travelling along a track through semi-analytical analyses, while Galvín et al. [Contribution 8] focus on railway bridges, proposing a time-frequency analysis based on wavelet transforms to separate forced and free vibration components from measured responses. The studies and methodologies provided represent valuable contributions to a deeper understanding of railway infrastructure behaviour.

Finally, Collina et al. [Contribution 9] address the growing importance of monitoring in modern railway systems, specifically investigating the feasibility of detecting contact wire rupture in high-speed railway catenary systems. Their study demonstrates the potential of vibration-based monitoring techniques to improve operational safety and enable the early detection of critical failures in railway infrastructure.

Collectively, the contributions of this Special Issue reflect the breadth and vitality of current research in railway dynamics and ground-borne vibrations. They span multiple spatial scales, from vehicle components and track systems to soil-structure interaction and urban environments, and integrate experimental, analytical, and numerical approaches. Together, they highlight the importance of interdisciplinary research in addressing the challenges posed by modern railway systems and in developing sustainable and resilient transportation infrastructure.