The development of railways stands as a pivotal milestone in the history of transportation, transforming the world and revolutionising the movement of people and goods. From their humble beginnings as rudimentary track systems to the sophisticated and interconnected networks we witness today, railways have played a crucial role in fostering economic growth, promoting globalisation, and shaping modern societies. Moreover, as the world grapples with the urgent need to mitigate climate change and transition to sustainable modes of transportation, the role of railways has gained significant attention. Railways have long been recognised as one of the most environmentally friendly means of mass transit, offering lower carbon emissions, energy efficiency, and reduced congestion compared to other transportation modes. However, there are still many challenges to overcome to provide continuous sustainability in the context of environmental impacts, especially related to wildlife and habitat protection. This scientific paper aims to explore the concept of sustainability in the context of railways, providing a comprehensive analysis of their environmental influences. As a result, the authors present a complex analysis of the topic, combining different perspectives—ecological, engineering, and legislative. They present methods of reducing noise pollution—constructional and legal ways; emission pollution reduction associated with combustion engines; and innovative analysis of limiting the impact of transportation on natural habitats and forest animal populations, which is not yet sufficiently elaborated scientifically in the literature. By examining key strategies, technologies, and policy frameworks, this research sheds light on the challenges and opportunities related to sustainability within the railway industry around the world.

The wheel-flat defect is one of the many issues decreasing the level of and comfort in light rail vehicles. The two main causes of wheel-flats are temporary or complete wheel blocking. The negative effect is the increase of the dynamic phenomenons in the wheel-rail interaction, which are impulsive in their nature. It could prove to be dangerous for the safety of the ride. Therefore, a regular wheel surface monitoring and wheel-flats detecting would be well-founded to the fast detection of a flat point and to take remedial measures. The main aim of the article is to present the algorithm, according to which the wheel-flat detection during tram passage is possible. Several vibration transducers were mounted on the rail and measured vibration amplitude during trams pass-by. The proposed method is based on the vibration signal processing in the time and frequency domain. The Hilbert transform was used in the algorithm and all research analyses. The carried out experimental study and the analysis of the results of the method, show a high efficiency in the wheel flat detection.

1 INTRODUCTION AND MAIN THEORETICAL ASPECTS

Increasing the speed of trains forces the application of a greater braking power, i.e. the capability of the brake system of rapidly absorbing and dispersing the stored heat energy. The instability of operation results from the occurrence of vibrations on the friction component, which affects the efficiency of the braking process. In practice, it means that when braking, the vehicle variable friction resistance may lead to an uneven braking process. The effects of such changes can be manifested in the form of vibrations with high input amplitude. The vibrations generated by the working components are distributed throughout the vehicle, which also adversely affects the driving comfort. The purpose of this paper is to determine the resonant frequencies of selected components of the railway disc brake. This paper presents a method of assessing the thickness of the brake pads of a railway disc brake based on the results of parameterization of the time-frequency map a(t, f) of vibrations generated by the brake components. Methods of time-frequency analysis were suggested as a tool of time-frequency selection of the vibration signal. The authors described an algorithm of the method and presented an example illustrating the application of the synchronously averaged short-time Fourier transform for the extraction of the signal components related to the braking process. As a result of parameterization of the map a(t, f) signal parameters, values covariant with the thickness of the disc brake were obtained.

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