Railway Network Research Articles

Periodic timetabling with integrated track choice for railway construction sites

We propose a mixed-integer linear programming model to generate and optimize periodic timetables with integrated track choice in the context of railway construction sites. When a section of a railway network becomes unavailable, the nearby areas are typically operated close to their capacity limits, and hence carefully modeling headways and allowing flexible routings becomes vital. We therefore discuss first how to integrate headway constraints into the Periodic Event Scheduling Problem (PESP) that do not only prevent overtaking, but also guarantee conflict-free timetables in general and particularly inside stations. Secondly, we introduce a turn-sensitive event-activity network, which is able to integrate routing alternatives for turnarounds at stations, e.g., turning at a platform vs. at a pocket track for metro-like systems. We propose several model formulations to include track choice, and finally evaluate them on six real construction site scenarios on the S-Bahn Berlin network.

Running safety analysis of a train-bridge coupled system under near-fault ground motions considering rupture directivity effects

The implementation of China’s high-speed railroad network and the “Bridges Instead of Roads” construction concept has raised concerns over earthquake safety. The complex mechanism of near-field ground motions poses greater risks than far-field ground motions due to the rupture directivity effect, and Hanging-wall/Footwall effects. The PEER earthquake database lacks earthquake records with fault distances less than 20 km, making it difficult to study train running safety (TRS) under near-fault ground motions. To address this issue, an empirical formulation method is adopted for near-fault three-dimensional seismic synthesis that considers source and site characteristics as well as rupture directivity effects using regression analysis. The method is verified with respect to directivity pulse and a train-bridge coupled system (TBCS) model is developed to verify its accuracy under earthquakes. Responses of the TBCS model under near-fault ground motions synthesized with different fault types, closest distances to the fault surface, and directivity parameters are analyzed by taking the average of the largest part of the response for comparison. Results show that dip-slip faults pose a greater danger than strike-slip faults, and the main reason for the hazard caused by rupture directivity effects is the generation of a forward directivity pulse, which makes the TBCS highly susceptible to derailment under near-fault pulse-like ground motions.

A Review and Comparison of Transformer and Static Frequency Converter Traction Supply Architectures for AC Electrified Railways

Electrification of the U.K. railway network will play a critical role in achieving targets of net-zero CO2 emissions while providing major benefits to train operators, passengers, and industry. In the drive to make electrification a more cost-effective prospect, this paper intends to complete a comparison of the common feeding arrangements and the novel Static Frequency Converter for use in AC electrification using PSCAD EMTDC simulations. The findings illustrate the performance of two classic architectures and autotransformer feeding compared to a proposed classic SFC arrangement and provide recommendations for SFC implementation with separations between feeder stations of up to 60 kilometres using a parallel feeding arrangement, along with demonstrating SFCs exhibiting more robust performance in the event of faults.

Multi-Objective Optimization for High-Speed Railway Network Based on “Demand–Supply–Management” Model

This paper develops a multi-objective optimization model for national high-speed railway network planning. Three objectives are proposed from the macro, meso, and micro perspectives, and these three objectives are considered simultaneously. Using real data, case studies are conducted to optimize China’s “four east–west and four north–south railway lines” network, which includes Beijing, Shanghai, Wuhan, Guangzhou, and Zhengzhou as main hubs. The results show that, on the one hand, the optimization model reduces the overlap between long-distance passengers and short-distance passengers on the high-speed railway line, facilitates the travel of passengers, and improves the line service capability; on the other hand, optimization of the network shortens the travel time of the passengers, reduces the cost of the railway, and improves the operation efficiency of the high-speed railway line network. The results show that the total travel time of all high-speed railway passengers in the optimization model is reduced by 18.4%, while the benefit rate of the operator increased by 21.99%.

Optimising railcar transfer chain via fuzzy programming and a simulated annealing algorithm

With the accelerated changes of trade and economic structure, the fluctuation of shipment size is increasing in railway transportation. Railway companies are facing continuous challenges about how to optimise railcar transfer chain to achieve the balance between the workload of railway network and daily changing transportation demands. In this paper, elastic capacity constraints are designed to solve the number fluctuation of railcars in shipments. We define available capacity belts to describe the elastic capacities of railway network, then fuzzy theory is introduced. A membership function is designed to designate the satisfaction degree for the number of railcars, and a non-linear integer programming model is developed. We test the model with two numerical examples from the 2019 Railway Applications Section Problem Solving Competition, and a simulated annealing algorithm is employed to solve the problem. In the experiment with 16 yards, the model generated 1304 variables. Furthermore, as the scale of the railway network increases, the number of variables exhibited exponential explosive growth. In the experiment with 32 yards, the model generated 76,037 variables and determined 365 direct train services, resulting in an operating cost of 245,014,388 car-hours. The results of the experiments effectively verify the effectiveness of the model.

The complexity of the timetable‐based railway network design problem

AbstractBecause of the long planning periods and their long life cycle, railway infrastructure has to be outlined long ahead. At the present, the infrastructure is designed while only little about the intended operation is known. Hence, the timetable and the operation are adjusted to the infrastructure. Since space, time and money for extension measures of railway infrastructure are limited, each modification has to be done carefully and long lasting and should be appropriate for the future unknown demand. To take this into account, we present the robust network design problem for railway infrastructure under capacity constraints and uncertain timetables. Here, we plan the required expansion measures for an uncertain long‐term timetable. We show that this problem is NP‐hard even when restricted to bipartite graphs and very simple timetables and present easier solvable special cases. This problem corresponds to the fixed‐charge network design problem where the expansion costs are minimized such that the timetable is conductible. We model this problem by an integer linear program using time expanded networks. To incorporate the uncertainty of the future timetable, we use a scenario‐based approach. We define scenarios with individual departure and arrival times and optional trains. The network is then optimized such that a given percentage of the scenarios can be operated while minimizing the expansion costs and potential penalty costs for not scheduled optional trains.

Study on the impact of the high-speed rail network on industrial structure upgrading

This paper explores the mechanism of the high-speed railway network for upgrading industrial structures. Based on social network analysis methods, this paper uses the sample data of 282 cities from 2011 to 2020 to measure the centrality of the sample cities in the high-speed railway network. The panel data model, mediation effect model, and spatial econometric model are used to explore the impact of high-speed railway networks on upgrading industrial structures. Finally, the following conclusions are drawn: (1) The development of China's high-speed railway network is unbalanced and insufficient, showing a pattern of higher development in the east and lower development in the West; (2) The high-speed railway network can significantly promote the upgrading of industrial structure, and this impact varies; (3) The high-speed railway network mainly affects the upgrading of the industrial structure by improving the concentration of innovation and capital factors, while the impact on the concentration of population factors is not very significant; (4) There are spatial spillover effects of the high-speed railway network on the upgrading of industrial structure, and the spillover effects of the railway network on neighboring areas are significantly higher than those on the local areas. Based on the above research conclusions, this paper proposes relevant policies to promote the development of urban high-speed railway networks, promote upgrading industrial structures, and achieve high-quality development of the region.

Energy model of a fuel cell hybrid-electric regional train in passenger transport service and vehicle-to-grid applications

Hydrogen fuel cell multiple unit vehicles are acquiring a central role in the transition process towards carbon neutral trains operation in non-electrified regional railway networks. In addition to their primary role as a transport mean, these vehicles offer significant potential for applications in innovative concepts such as smart grids. Compared to the pure electric propulsion systems, fuel cell technology allows for cogeneration processes by recovering generated heat in addition to the provision of the electrical power. This paper presents the analysis of fuel cell hybrid-electric multiple unit vehicle employed in regional railway transport during regular service, and in vehicle-to-grid application during the off-service hours, providing the electrical and thermal energy for stationary consumers in terminal stations. The system dynamics are modelled using a backward-looking quasi-static simulation approach, with implemented real-time optimization-based control strategy for managing the power flows between different components. In a case study of selected vehicle and railway services in the Netherlands, the fuel cell system showed average hydrogen consumption of 0.4 kg/km, with the overall electrical efficiency of 38.89%. In vehicle-to-grid scenario, the system satisfied complete stationary power demand, and provided about 327 kWh of thermal energy during 2-h operation, reaching the overall cogeneration efficiency of 66.81%.

New evidence of high-speed rail promoting green economic growth in the Yangtze River Economic Belt: empirical analysis based on difference-in-differences.

The Yangtze River Economic Belt (YREB) is an important ecological barrier in China. From new perspectives, this paper explores the mechanism of high-speed rail (HSR) for green economic growth (GEG) in the YREB. This paper constructs 108 city panel data at the prefecture level and above in the YREB from 2003 to 2020. Difference-in-differences (DID) is adopted to research the impact of high-speed rail on GEG in the YREB. (1) HSR has significantly improved the GEG of the YREB. The effect value is 4.88%. The parallel trend test suggests that DID is valid. A time-varying instrumental variable combining average altitude and historical railway network is constructed for the endogeneity test. (2) Propensity score matching (PSM) and DID (PSM-DID) were employed to test the sample selection bias. (3) A battery of robustness tests, including the placebo test, variable replacement, and policy interference exclusion, is carried out. The conclusions are still valid. (4) HSR can promote the GEG of the YREB by encouraging technological innovation, industrial upgrading, and increasing ecological efficiency. The contribution rate from the largest to the smallest is ecological efficiency, industrial upgrading, and technological innovation. (5) Heterogeneity analysis shows that HSR has played an important role in encouraging GEG in the eastern, peripheral cities, and the downstream cities of the YREB. Finally, this paper puts forward policy suggestions for promoting GEG in the YREB.

Rail wear rate on the Belgian railway network – a big-data analysis

ABSTRACT This paper presents a big data-based analysis of the rail wear of the whole Belgian railway network measured in 2012 and 2019. Wear rates are reported, discussed, and quantitatively formulated as functions of critical factors in terms of curve radius, annual tonnage (rail age), high rail in curves, an average from both rails in straight tracks at rail top (vertical wear) and gauge corner (45° wear) and for steel grade R200 and R260. The influence of preventive grinding is also analysed. The wear rates are derived in an aggregated manner for the whole network. The wear rates do not show significant change with changes in rolling stock over the years, implying that the wear rates could also hold for other networks. It is found that R200 shows, on average, a 34% higher wear rate than R260. Also, the wear rate per tonnage is lower for high-loaded tracks. Thus, time is a relevant factor in explaining the wear evolution of low-loaded tracks; for instance, the effect of corrosion may have an important role. The paper provides statistically significant information that can be used for wear modelling, understanding and treating rolling contact fatigue based on the wear rate and developing tailored rail maintenance strategies.

Delay prediction with spatial–temporal bi-directional LSTM in railway network

Train delay prediction is a vital part of railway system, but due to uncertain factors such as the complexity of the railway system and spatial–temporal features, it is often difficult to predict train delay in practice. In this paper, we propose a Spatial–Temporal and Bi-directional Long Short-Term Memory (ST-BiLSTM) model to deal with the train delay prediction problem. The model contains spatial–temporal blocks to capture spatial and temporal features and a bi-directional Long Short-Term Memory (LSTM) block to introduce bi-directional information through an attention mechanism. Experiments demonstrate that ST-BiLSTM outperforms the existing baselines in two evaluation metrics.

Characteristics of Channel Spreading Function and Performance of OTFS in High-Speed Railway

Orthogonal time frequency space (OTFS) modulation is an emerging technology to tackle time-frequency (TF) selective channel in high mobility scenarios. In OTFS, resource is multiplexed in the delay-Doppler (DD) domain. Based on the potential sparsity, separability, stability and compactness of the channel spreading function, OTFS is able to realize lower complexity of channel estimation, higher diversity and higher reliability compared with orthogonal frequency division multiplexing (OFDM). However, the channel spreading function for practical communication systems is rarely considered in the current OTFS-related literature. High-speed railway (HSR) is a typical high mobility scenario with trains travelling at over 200km/h, which has the potential to employ OTFS. To this end, the HSR channel spreading function is characterized and the performance of OTFS in HSR is evaluated based on the realistic channel measurement in this article. Firstly, the HSR channel in TF domain is measured based on the long term evolution railway (LTE-R) network. Then, the characteristics of the channel spreading function are analyzed. In particular, the impact of time domain channel fading on the spreading function is investigated. The characteristics of the measured spreading function are analyzed with the proposed metrics in railway viaduct and tunnel scenarios. Based on the above analysis, an algorithm for generating the channel spreading function is proposed. Feasibility of the proposed DD domain channel generation algorithm is verified through comparing metrics of which to those of the measured channel. By simulating the bit error rate (BER) and mean square channel estimation error performances of OTFS modulation in the practical band-limited systems, it is shown that the impacts of Doppler shift, delay, SFFT and time domain channel fading need be considered for the application of OTFS modulation, in contrast to the state-of-art DD domain channel generation scheme based on tap delay link (TDL) model. For example, compared to OTFS modulation under the ideal channel spreading function, OTFS modulation requires a signal gain greater than 5 dB under the practical channel spreading function affected by above factors, to achieve the same BER less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> under the parameters and algorithms given in section V.

Digital twinning during load tests of railway bridges - case study: the high-speed railway network, Extremadura, Spain

This article presents a case study with various developments of digital twinning of a sample of load tests performed on several railways bridges. The case study is located in Extremadura, South Western Spain and its aim is the generation of a validated, multi-layered information construct in the form of a digital twin as the result of a load test. This result is conceived, not only to verify the assumptions of the design of the bridge but also, to optimize future maintenance plans of the network. This particular case study is framed within a vaster European effort on digitization of the construction sector. Research and Innovation Actions within this demo case are aimed at integrating routine requirements and procedures of load tests with cutting edge digital technologies for the generation of validated virtual replica of these physical bridges. The generated twins during these load tests behaviourally match the obtained response during loading and as such, represent an ideal model for future simulations and behavioural predictions. Different data-gathering techniques and numerical models are integrated within a Common Data Environment (CDE). All efforts related to measurement, simulation, 3D modelling, assessment and validation can be wrapped up systematically for further use during regular operation of the asset.

ASSESSMENT OF PROSPECTS FOR THE IMPLEMENTATION OF HIGH-SPEED TRAFFIC ON RAILWAYS OF UKRAINE

The development of Ukraine's economy and industry largely depends on the use of its transit potential, which will contribute not only to the intensification of transit cargo flows, but also to an increase in passenger traffic. Even in the conditions of martial law, railway transport performs its functions of mass transportation of goods and passengers rather stably. However, the efficiency of railway transport is mainly provided by freight transport, which makes it much more difficult to compete with other modes of transport in the field of passenger transport. In today's realities on the market of transport services regarding the provision of passenger transportation, there is a decline in the position of railway transport But, despite this, railway transport remains strategically important, as it ensures the transportation of goods and the evacuation of the population in difficult times for our country. In addition, the railway network of Ukraine organically fits into the European network through Poland, Moldova, Hungary, Romania and Slovakia. All this determines that the process of European integration of Ukraine requires modern approaches from the railway, one of which is the introduction of high-speed traffic. As world experience shows, the introduction of high-speed traffic is necessary to increase the efficiency of railway passenger transportation and attract customers to railway services. In accordance with this, the article discusses the prospects for the introduction of high-speed traffic on the highways of Ukraine. At the first stage, the justification of the choice of the mode of transport is carried out based on the provisions of the theory of fuzzy sets, which makes it possible to determine the most competitive mode of transport. At the second stage, a comprehensive assessment of the prospects for the introduction of highspeed traffic is carried out, which determined the need to assess the economic efficiency of this type of transport, taking into account the reconstruction of the existing railway lines of Ukraine. Therefore, the introduction of high-speed traffic will allow to strengthen the competitive advantages of railway transport in the field of passenger transportation, and will also contribute to the European integration processes in Ukraine.

Performance evaluation of rail trackbed stiffness: pre and post stabilisation

Excessive deflection of a rail in response to axle loading can lead to discomfort for passengers and increased wear of both railway structures and trains. These oscillations are often caused by poor trackbed stiffness which may be due to either soft subgrade and/or contaminated ballast. A variety of trackbed stabilisation (TBS) techniques are available to remediate soft subgrades and increase the safety of tracks within the railway network. Traditional TBS methods require track removal, which is expensive, disruptive and often inefficient maintenance works. Micro-piling, using screw piles installed between sleepers, is an innovative low disruption TBS technique. This paper investigates the performance of a soft subgrade and contaminated ballast section of rail line in the UK, before and after screw pile TBS. Pre and post remediation, a computer vision-based system was used to measure rail vertical deflections during train passages and then analysed to quantify the trackbed stiffness. Additionally, 3D finite element models are created and validated by the site measurements. The finite element models are used to simulate a range of different scenarios exploring how changes to the TBS piling layout and/or further works, such as ballast improvement could add further improvements or design efficiencies. Site measurements show TBS reduced rail deflection by 20–30%, indicating that micro-piling is an effective technique for soft subgrades. The finite element analysis revealed the efficiency of micro-piling is highly dependent on the conditions of ballast, strength of the ground at the pile toe, and the pile arrangement. When the aforementioned are optimised the rail deflection could be reduced to approximately 50% of the pre TBS condition.

Regional Transformation via Rail: A Historical and Analytical Examination of Iran's Railway Network and its Socio-Economic Impacts

Regional Transformation via Rail: A Historical and Analytical Examination of Iran's Railway Network and its Socio-Economic Impacts

Feasibility of establishing an integrated railway-based containerised cargo transport network between the Port of Colombo and free trade zones in Sri Lanka

A large percentage of Sri Lanka's exports and imports are generated by the manufacturing sector and originates from facilities dispersed throughout Export Processing Zones (EPZs) around the country. An efficient hinterland transport network is required between the Port of Colombo and these EPZs. However, road trucks are used as the dominant transport mode for moving containerised cargo to/from Colombo Port. This study proposes a dry port-based containerised import/export cargo transportation method using a railway network to connect the Port of Colombo and the EPZs under several alternative network configurations. This study conducts a questionnaire survey with 40 experts to identify issues with the current road-based container transport network and ascertain the benefits of proposed railway-based networks in Sri Lanka. A majority of respondents highlight the benefits of the proposed network from multiple perspectives along with several drawbacks with the current road-based network. Initially, the feasibility of two alternative dry port locations in Orugodawatta and Kerawalapitiya are analysed. A mathematical model is developed to analyse the feasibility of the proposed alternative networks. Finally, the optimum dry port location is selected as Aluthwaththa using a simulation-based Greenfield analysis approach. Results highlight the advantages of proposed networks under several scenarios. The study demonstrates a systematic approach to decision-making by optimising the local cargo handling process, where, Sri Lankan inland logistic operations will become more efficient, with total transport costs, environmental pollution, and transportation time decreasing significantly.

An Integrated Optimization Method of High-Speed Railway Rescheduling Problem at the Network Level

For high-speed railway operations at the network level, unforeseen events that lead to operation interruptions are inevitable, which should be handled within a short period of time to reduce the influence of the events as much as possible. This paper introduces an integrated optimization method to deal with rescheduling problems at the railway network level under emergencies, rescheduling the train timetable, and utilizing the train sets. train set A three-objective optimization model is proposed with the aim of minimizing additional operation costs, total delay, and the number of transfer passengers. Then, an algorithm based on NSGA-III is proposed to solve the model. Computational experiments on real data are conducted to show the adaptability of the model and algorithm. The average optimization rate of the three objectives is 12.12%, 14.12%, and 10.57%, indicating the effectiveness of the method. Moreover, more experiments on a railway network in China are being conducted to analyze which section and which time have the greatest impact on the railway network when emergencies occur. According to the experiment, the bottleneck section is section 15, and the bottleneck time is 11:00 am. In addition, the importance of all the depots is discussed, and depot II is selected as the most important depot.

Spatio-Temporal Evolution of Urban Expansion along Suburban Railway Lines in Megacities Based on Multi-Source Data: A Case Study of Beijing, China

Suburban railways in megacities exert a pivotal role in propelling urbanization and shaping urban agglomeration. However, previous study endeavors have overlooked the transformations occurring in urban expansion along suburban railways, with a particular dearth of attention on the spatio-temporal evolution of landscape ecology and urban function. Therefore, this study employs the megacity of Beijing as an example. It utilizes remote sensing and point-of-interest (POI) data spanning from 2008 to 2022 to construct an indicator system from two essential dimensions: urban form and function. We explored the spatio-temporal characteristics of alterations in urban expansion within the gradient buffer zone adjacent to the suburban railway network in Beijing. The results showed that: (1) The rates of urban expansion were highest in 2008–2013 and lowest in 2013–2018; moreover, suburban railways had the greatest impact on the built-up area within 2–4 km along the route, and the impact gradually decreased beyond 4 km. (2) The direction of urban expansion shifted northward in the direction of latitude and eastward in the direction of longitude from 2008 to 2022, with the shift in latitude being more distinct. (3) The number of urban functions gradually increased from 2008 to 2018, but the number of medical services suddenly increased and the number of other urban functions decreased from 2018 to 2022; in addition, urban functions other than scenic spots were mainly distributed in the main urban areas, with very few clusters distributed near stations. (4) The landscape shape index became more irregular and fragmented from the center along the route to the edge of the buffer zone from 2008 to 2013, and the degree of fragmentation was highest in the 2–4 km buffer zone. In summary, this paper analyzes the spatio-temporal characteristics of urban expansion along suburban railways through four indexes, namely expansion rate, expansion direction, urban function, and landscape shape, and the results of this study are of great significance to the development and planning of suburban railways in megacities.

Capacity-constrained mean-excess equilibrium assignment method for railway networks

The reliability and unreliability of travel time variability caused by stochastic train delays considerably influence passengers’ travel path choices. This paper proposes an equilibrium assignment method that can capture the passengers’ path choice behaviors considering both the reliability and unreliability of travel time variability in the railway network. The passengers’ travel path choices are modeled using the mean-excess travel cost (METC), which is the combination of the conditional expectation of travel cost exceeding the effective travel cost, and the endogenous advanced ticket booking cost associated with the rigid train capacity. In general, heterogeneous passengers with different risk-aversion attitudes toward stochastic train delays evaluate their travel options differently and have different requirements for successful transfer. Therefore, first, the passengers’ transfer options are modeled with the concept of METC based on the delay distribution of the two connecting trains. Subsequently, the METC of the passenger trips is calculated. A mean-excess passenger flow assignment model is formulated based on the user equilibrium condition. A path-based capacity-constrained passenger assignment algorithm is designed to solve the model. Moreover, three illustrative examples are presented to demonstrate the effectiveness of the model and solution algorithm.