Facing the high demand for faster and heavier freight trains in Australia, researchers and practitioners are endeavouring to develop more innovative and resilient ballasted tracks. In recent years, many studies have been conducted by the researchers from Transport Research Centre at the University of Technology Sydney (TRC-UTS) to examine the feasibility of incorporating recycled tyre/rubber into rail tracks. This paper reviews three innovative applications using recycled rubber products such as (1) a synthetic energy-absorbing layer for railway subballast using a composite of rubber crumbs and mining by-products, (2) using rubber intermixed ballast stratum to replace conventional ballast, and (3) installing recycled rubber mat to mitigate ballast degradation under the impact loading. Comprehensive laboratory and field tests as well as numerical modelling have been conducted to examine the performance of rail tracks incorporating these innovative inclusions. The laboratory and field test results and numerical modelling reveal that incorporating these rubber products could increase the energy-absorbing capacity of the track, and mitigate the ballast breakage and settlement significantly, hence increasing the track stability. The research outcomes will facilitate a better understanding of the performance of ballast tracks incorporating these resilient waste tyre materials while promoting more economical and environmentally sustainable tracks for greater passenger comfort and increased safety.

Rolling noise is produced by vibration of the wheels and track, induced by their combined surface roughness. It is important to know the relative contributions of the different sources, as this affects noise control strategies as well as acceptance testing of new rolling stock. Three different techniques are described that aim to use pass-by measurements to separate the wheel and track components of rolling noise. One is based on the TWINS model, which is tuned to measured track vibration. The second is based on the advanced transfer path analysis method, which provides an entirely experimental assessment. The third is based on the pass-by analysis method in combination with static vibroacoustic transfer functions which are obtained using a reciprocity method. The development of these methods is described and comparisons between them are presented using the results from three experimental measurement campaigns. These covered a metro train, a regional train and a high-speed train at a range of speeds. The various methods agree reasonably well in terms of overall trends, with moderate agreement in the mid-frequency region, and less consistent results at low and high frequency.

Replacing the energy density and convenience of diesel fuel for all forms of fossil fuel-powered trains presents significant challenges. Unlike the traditional evolutions of rail which has largely self-optimised to different fuels and cost structures over 150 years, the challenges now present with a timeline of just a few decades. Fortunately, unlike the mid-1800s, simulation and modelling tools are now quite advanced and a full range of scenarios of operations and train trips can be simulated before new traction systems are designed. Full trip simulations of large heavy haul trains or high speed passenger trains are routinely completed controlled by emulations of human drivers or automated control systems providing controls of the “virtual train”. Recent developments in digital twins can be used to develop flexible and dynamic models of passenger and freight rail systems to support the new complexities of decarbonisation efforts. Interactions between many different traction components and the train multibody system can be considered as a system of systems. Adopting this multi-modelling paradigm enables the secure and integrated interfacing of diverse models. This paper demonstrates the application of the multi-modelling approach to develop digital twins for rail decarbonisation traction and it presents physics-based multi-models that include key components required for studying rail decarbonisation problems. Specifically, the challenge of evaluating zero-emission options is addressed by adding further layers of modelling to the existing fully detailed multibody dynamics simulations. The additional layers detail control options, energy storage, the alternate traction system components and energy management systems. These traction system components may include both electrical system and inertia dynamics models to accurately represent the driveline and control systems. This paper presents case study examples of full trip scenarios of both long haul freight trains and higher speed passenger trains. These results demonstrate the many complex scenarios that are difficult to anticipate. Flowing on from this, risks can be assessed and practical designs of zero-emission systems can be proposed along with the required recharging or refuelling systems.

Urban transportation systems are facing severe challenges due to the rapid growth of the urban population, especially in China. Suspended monorail system (SMS), as a sky rail transportation form, can effectively alleviate urban traffic congestion due to its independent right-of-way and minimal ground footprint. However, the SMS possesses a special traveling system with unique vehicle structure and bridge configuration, which results in significant differences in both the mechanisms and dynamics problems associated with train–bridge interaction (TBI) when contrasted with those of traditional railway systems. Therefore, a thorough understanding of the SMS dynamics is essential for ensuring the operational safety of the system. This article presents a state-of-the-art review of the TBI modeling methodologies, critical dynamic features, field tests, and practice of the SMS in China. Firstly, the development history, technical features, and potential dynamics problems of the SMS are briefly described, followed by the mechanical characteristics and mechanisms of the train–bridge interactive systems. Then, the modeling methodology of the fundamental elements in the suspended monorail TBI is systematically reviewed, including the suspended train subsystem, bridge subsystem, train–bridge interaction relationships, system excitations, and solution method. Further, the typical dynamic features of the TBI under various operational scenarios are elaborated, including different train speeds, a variety of line sections, and a natural wind environment. Finally, the first new energy-based SMS test line in the world is systematically introduced, including the composition and functionality of the system, the details of the conducted field tests, and the measured results of the typical dynamic responses. At the end of the paper, both the guidance on further improvement of the SMS and future research topics are proposed.

The China comprehensive inspection train (CIT) is designed for evaluating railway infrastructure to ensure safe railway operations. The CIT integrates an array of inspection devices, capable of simultaneously assessing railway health condition parameters. The CIT450, representing the second generation, can reach a top speed of 450 km/h with inspection on the infrastructure. This paper begins by outlining the global evolution of inspection trains. It then focuses on the critical technologies underlying the CIT450, which include: (1) real-time inspection data acquisition with spatial and temporal synchronization; (2) intelligent fusion and centralized management of multi-source inspection data, enabling remote supervision of the inspection process; (3) technologies in inspecting track, train–track interaction, catenary, signalling systems, and train operating environment; and (4) AI-driven analysis and correlation of inspection data. The future developmental directions for comprehensive inspection trains are discussed finally. The CIT450’s approach to real-time railway health monitoring can enrich traditional inspection means, operational, and maintenance methods by enhancing inspection efficiency and automating railway maintenance.

The regenerative braking energy utilization system (RBEUS) stands as a promising technique for improving the efficiency and power quality of electrified railways. Beyond the vital aspects of energy management and control strategies, ensuring fault protection is paramount for the secure and steady operation of the traction power supply system (TPSS) integrated with RBEUS. This paper introduces an innovative protection scheme tailored to diverse RBEUS application scenarios. Firstly, fault categories are streamlined into three levels: system, equipment, and warning. Subsequently, a novel multi-port active power differential protection method, aligned with RBEUS operational principles, is crafted to serve as a comprehensive and sensitive main protection. Building upon this foundation, a hierarchical protection structure for RBEUS is established, addressing the intricacies and variations in fault types while boosting anti-disturbance capabilities under faulty conditions. Embracing the principle of railway-oriented safety, a collaborative RBEUS-TPSS protection scheme is put forth. Finally, through simulated scenarios encompassing various fault conditions, the proposed scheme’s feasibility and effectiveness are convincingly validated.

Nonuniform track support and differential settlements are commonly observed in bridge approaches where the ballast layer can develop gaps at crosstie-ballast interfaces often referred to as a hanging crosstie condition. Hanging crossties usually yield unfavorable dynamic effects such as higher wheel loads, which negatively impact the serviceability and safety of railway operations. Hence, a better understanding of the mechanisms that cause hanging crossties and their effects on the ballast layer load-deformation characteristics is necessary. Since the ballast layer is a particulate medium, the discrete element method (DEM), which simulates ballast particle interactions individually, is ideal to explore the interparticle contact forces and ballast movements under dynamic wheel loading. Accurate representations of the dynamic loads from the train and track superstructure are needed for high-fidelity DEM modeling. This paper introduces an integrated modeling approach, which couples a single-crosstie DEM ballast model with a train–track–bridge (TTB) model using a proportional–integral–derivative control loop. The TTB–DEM model was validated with field measurements, and the coupled model calculates similar crosstie displacements as the TTB model. The TTB–DEM provided new insights into the ballast particle-scale behavior, which the TTB model alone cannot explore. The TTB–DEM coupling approach identified detrimental effects of hanging crossties on adjacent crossties, which were found to experience drastic vibrations and large ballast contact force concentrations.

Rolling noise is an important source of railway noise and depends also on the dynamic behaviour of a railway track. This is characterized by the point or transfer mobility and the track decay rate, which depend on a number of track parameters. One possible reason for deviations between simulated and measured results for the dynamic track behaviour is the uncertainty of the value of some track parameters used as input for the simulation. This in turn results in an uncertainty in the simulation results. In this contribution, it is proposed to use the general transformation method to assess a uncertainty band for the results. Most relevant input parameters for determining the point input mobility and the track decay rate for a ballasted track are analysed with regard to the uncertainties and for the value of each an interval is determined. Then, the general transformation method is applied to four different simulation methods, working both in the frequency and time domains. For one example track, the resulting uncertainty bands are compared to one dataset with measurements for the point mobility and the track decay rate. In addition, a sensitivity analysis is performed to determine the parameters that significantly influence the overall result. While all four simulation methods produce broad uncertainty bands for the results, none did match the measured results for the point mobility and the track decay rate over the entire frequency range considered. Besides the large influence of the uncertain pad stiffness, it turned out that the rail wear is also a significant source of uncertainty of the results. Overall, it is demonstrated that the proposed approach allows assessing the influence of uncertain input parameters in detail.

Arrival headway, the minimum time interval between two trains that consecutively stop in the same railway yard, significantly influences overall railway capacity and becomes a bottleneck in large high-speed railway yards. This occurs because the leading train slows considerably along the long receiving route to the yard; while, the following train continues at top speed, creating a substantial spatial and temporal interval between them. This paper proposes a speed profile intervention (SPI) approach to reduce arrival headway. By setting appropriate speed limits in specific block sections for each train, the following train decelerates in advance, thereby shortening the interval with its predecessor. We first study the impact of speed values and locations on arrival headway theoretically, then validate our findings through a multi-agent simulation approach to quantitatively investigate the relationship between headway and SPI parameters. Simulation experiments using real-world data from the Beijing–Shanghai high-speed railway demonstrate that the SPI approach can significantly reduce arrival headway without any infrastructure modifications. To mitigate potential side effects on travel time associated with this approach, we perform an analysis that involves setting appropriate speed limit values and selecting strategic locations for their implementation.