Urban Railway Lines Research Articles

Reducing low-frequency noise radiation from a concrete box girder bridge using acoustic short circuits

Low-frequency noise (20–200 Hz) radiated from concrete box girder bridges on urban viaduct railway lines is a significant source of disturbance to nearby residents. Many researchers have investigated methods which can be used to effectively reduce this bridge noise. Currently, most of the methods are based on the principles of vibration isolation and/or absorption. This paper, after modelling and analysing the contributions of various parts of a concrete box girder bridge to the total noise radiated from the bridge, presents a study on the potential in bridge noise control of making holes to create acoustic short circuits on the bridge wings. It is found that by this means the bridge noise can be reduced by up to 6.8 dB at standard-specified measurement points. Additionally, a 3dB-effectiveness distance ratio design method for acoustic short-circuiting is proposed, which effectively reduces bridge noise and achieves stable noise reduction outcomes.

Evaluation of Fire Suppression Performance for Multiple-Fire-Source Fire Using Water Mist-Type Fire-Suppression Equipment for Railway Passenger Cabin

The fire suppression performance of a mist fire-extinguishing system in railway passenger cabin was evaluated using a performance evaluation method based on multiple fire sources. Scenarios were analyzed for a simulated space in the railway vehicle cabin of the Daegu Urban Railway Line 3 using automatic fire-suppression system methods based on railway-vehicle technical standards. Three n-heptane fire pools were positioned inside the test space. When the spray fire-extinguishing equipment was operated at 10 and 20 bar after 30 s of ignition, the variations in the temperature of the test space and the fire-extinguishing characteristics, such as the time taken to stop the fire-extinguishing equipment, were analyzed. The experimental results showed that the internal temperature of the cabin initially increased after ignition. However, when the fire- extinguishing equipment was operated 30 s after ignition, the internal temperature of the cabin stopped increasing and started to decrease, satisfying the fire safety standard that the fire must be completely extinguished within 5 min. The temperature decreased more rapidly when the operating pressure was 20 bar than when it was 10 bar. In addition, the vertical temperature distribution analysis showed that the temperature of the upper part was higher than that of the lower part, owing to thermal buoyancy. However, the design of the nozzle location is critical because the temperature decreases more slowly far from the nozzle of the mist fire-extinguishing system, which can be dangerous.

Load-current demand forecasting in substations of urban railway lines

Load-current forecasting is important in the operation and energy management of urban railway lines. It helps control strategies to manage and distribute energy optimally, thereby saving energy and reducing voltage fluctuations. This paper presents a method to predict the traction current at the busbar of a substation using the supervised machine learning algorithm. Because the traction power load is supplied from both adjacent traction power stations, and the energy exchange process between trains also takes place during work, the input data are selected to combine the value history of busbar currents and feeder currents. Besides, the neural network configuration and the number of training cycles in the estimated model can be adjusted to achieve the desired accuracy. The proposed method was tested and adjusted based on the actual operation data at the Lang traction station on 24 June, 2022. The estimated results compared with measurement data from the supervisory control and data acquisition (SCADA) have proven that the largest absolute error is no more than 5 (A). The maximum relative error is not more than 0.005, and the mean squared error does not exceed 0.01 over the whole operating time of a day from 4h45 to 22h45.

A train reaction: the infrastructural politics and mobility injustices accompanying Hanoi's new urban railway Line 2A

In 2008, Vietnam's Prime Minister approved the construction of the ‘Hanoi Urban Railway System’, a major infrastructure project for the country's capital city. The construction of Line 2A, the first line of this 8‐line railway, took ten years to complete, and was finally inaugurated in November 2021. Spanning 13 km across the city centre, Line 2A encountered more than just construction setbacks, with its reputation tarnished by contractor choice, accidents, and public scepticism over safety and accessibility. Sowing further seeds of doubt in the minds of many Hanoi residents is the fact that two‐thirds of the original financing came from preferential loans from Vietnam's large northern neighbour, conditional on the contractor and key materials being sourced from Vietnam's large, northern neighbour. Moreover, the project is informally categorized as part of Vietnam's large northern neighbour's Belt and Road Initiative. Drawing from conceptual literature regarding infrastructural politics and mobility (in)justice, we analyse how Hanoi residents have experienced and negotiated the construction of this Chinese‐Vietnamese infrastructure project. In particular, we consider how the livelihoods of those directly affected by the railway's operations, namely motorbike taxi‐drivers, have been impacted to date.

A Methodology for Continuous Monitoring of Rail Corrugation on Subway Lines Based on Axlebox Acceleration Measurements

Rail corrugation is a degradation phenomenon that manifests as a quasi-periodic irregularity on the running surface of the rail. It is a critical problem for urban railway lines because it induces ground-borne vibrations transmitted to the buildings near the infrastructure, causing complaints from the inhabitants. A typical treatment to mitigate the rail corrugation problem is the periodic grinding of the rails, performed by dedicated vehicles. The scheduling of rail maintenance is particularly critical because it can be performed only when the service is interrupted. A procedure for the continuous monitoring of rail corrugation is proposed, based on axlebox acceleration measurements. The rail irregularity is estimated from the measured acceleration by means of a frequency domain model of vertical dynamics of the wheel–rail interaction. The results obtained by using two different methods (a state-of-the-art method and a new one) are compared. Finally, the study of the evolution of the power content of the rail irregularity enables the identification of the track sections where corrugation is developing and rail grinding is necessary.

Max-Min-Plus-Scaling Systems in a Discrete-Event Framework with an Application in Urban Railway

In this paper we discuss modelling and control of discrete-event systems using max-min-plus-scaling systems. We analyse how the basic operations max, min, plus, and scaling occur in the modelling phase and we discuss some general forms for the system. Because of the different/deviating character of the signals in a discrete-event MMPS model, we will discuss concepts such as time-invariance and steady-state behavior. In the design of a model predictive controller for MMPS systems we have to revisit the cost functions in light of the discrete-event nature of the signals. We finalize this paper with the an intuitive case study on an urban railway line, performing both modelling and control.

A Matheuristic for the Integrated Disruption Management of Traffic, Passengers and Stations in Urban Railway Lines

In big cities, the metro lines usually face great pressure caused by huge passengers demand, especially during peak hours. When disruptions occur, passengers accumulate quickly at stations. It is of great importance for dispatchers to take passenger flow control into consideration for the traffic management to ensure passengers’ safety and to maintain their satisfaction. This paper proposes an integrated disruption management model, which incorporates train rescheduling and passenger flow control. In this model, the train services can be short-turned, cancelled and rerouted, while the number of passengers entering a station is managed by controlling the station gates with consideration of the capacities of platforms and trains. Moreover, the number of passengers arriving at a station is calculated according to the origin-destination matrices. The objectives are to recover the train operation to the original timetable as soon as possible and to minimize the waiting time of passengers outside the stations. With the interaction between train services, passengers and station gates, an iterative metaheuristic approach is proposed to solve the integrated disruption management problem. Based on the data of a Beijing metro line, numerical experiments are conducted to test the proposed algorithm. The results demonstrate the importance of integrated disruption management and the effectiveness of our solution method.

Reliability of Accessibility: An Interpreted Approach to Understanding Time-Varying Transit Accessibility

Variable traffic conditions cause travel time uncertainty and further lead to time-varying accessibility. Most current studies do not fully consider fluctuations in accessibility and use complicated methods that likely overestimate the level of accessibility and hinder the application of accessibility measures. To address this issue, we utilized large-scale open-source data and proposed an interpretation of the reliability of accessibility concept that incorporates reliability, travel time uncertainty, and a cumulative opportunity measure. We examined the reliability of accessibility to Shenzhen, a major city in China, focusing on transit accessibility and job opportunities. The results demonstrate that the reliability of accessibility displays a bimodal distribution along urban railway lines and can be used to calculate the impact of urban railways in terms of punctuality. The new approach illustrates time-varying characteristics in the form of probabilities and provides further guidance on accessibility for governments.

Optimization of supercapacitor’s location and capacity in the urban railway lines based on greedy principle

Using energy storage equipment is an effective solution to improve energy efficiency for urban railway lines. Two of the important parameters are the location and capacity of the storage device that will determine the efficiency of the power supply system. This paper presents an algorithm that combines the greed principle and the retrieval principle to determine the optimal location and capacity of supercapacitor storage stations along the track to maximize the economic benefits. The proposed algorithm is tested on a simulation model built based on the data of the Cat Linh - Ha Dong urban railway line. The simulation results show that the optimal installation of energy storage stations will increase maximum energy efficiency to contribute to economic growth and reduce the load peaks that will be reducing voltage fluctuations.

Optimal supercapacitor placement in an urban railway line

Supercapacitors (SCs) are important devices used in renewable energy storage applications on urban railways due to their high power density, good performance, and long maintenance-free lifetime. The position and capacity of supercapacitors play an essential role in increasing energy efficiency and improving the operating condition of the power supply system. This paper proposes an optimal methodology to place a supercapacitor energy storage system (SESS) for urban railway lines. The proposed method uses simulation tools to determine the level of renewable energy as well as the cycle of renewable energy occurrence at substations. Next, based on the working characteristics of the supercapacitor to calculate the accumulated energy that can be reused. Finally, the problem of the optimal siting and sizing of the SESSs is solved to maximize the economic benefits. A case study is applied to evaluate the algorithm. The simulation results demonstrate that installing the optimal SESS can increase energy efficiency, lower transient power, and the solution found is the best choice for economic goals

Efficiencies of the urban railway lines incorporating financial performance and in-vehicle congestion in the Tokyo Metropolitan Area

This study reviews the operations in 18 lines of seven major urban railway operators in the Tokyo Metropolitan Area and empirically evaluates their efficiencies while incorporating financial performance and in-vehicle congestion. The data were collected from statistical sources publicly available in Japan, and they contain in-vehicle congestion rates, line lengths, number of stations, vehicle kilometers, number of passengers, passenger kilometers, operating revenues by railway line, and operating expenses by operator in 2017. The line-level efficiencies of the operational efficiency, cost efficiency, and revenue efficiency were analyzed using data envelopment analyses, and Tobit regression was applied to examine how in-vehicle congestion rates are associated with these efficiencies. The efficiency analysis results showed that incorporating the in-vehicle congestion rate into operational efficiency enables to reflect the quality-of-service of the railway operation into the efficiency scores. Moreover, higher in-vehicle congestion rate leads to a lower cost efficiency but a higher revenue efficiency. The possible measures to improve efficiencies were discussed as per the categories of lines.

Integrated Optimization of Line Planning, Timetabling and Rolling Stock Allocation for Urban Railway Lines

In order to improve train operation planning from the two perspectives of enterprise operating costs and passengers’ travel time, this paper proposes an integrated optimization model of three sub-problems, namely line planning, timetabling and rolling stock allocation for urban railway transit lines based on passengers’ travelling demands and the constraints of the urban rail line. The model features dwelling time at stations, turnaround operations at terminal stations, entering/exiting depot operations and an assignment for passengers’ travelling flow. We propose a solution method based on a metaheuristic method that simulates annealing to generate an optimal solution for the overall problem using MATLAB. Finally, we use the example of Xi’an metro line one to demonstrate the performance of the model.

Urban Railway Development in Hanoi and the Possible Impacts on Mode Shifting: Experiences from Young Transport Users

This study aims to explore the travel behaviour of young travel group to understand different factors that could influence their mode choices, and their willingness to shift to the first urban railway line in Hanoi. This will help notify a range of measures that could be considered to decrease motorcycle usage and facilitate mode shift to public transport system. With the data collected from 396 students in five universities in Hanoi, Vietnam, a conditional logit regression model was developed to explore individual and alternative specific variables influencing the mode choice for studying trips. Key findings show that current mode usage, especially the dominant of motorcycle riding, having a strong effect on the tentative choice of Cat Linh – Ha Dong railway as a means of travelling to universities. Research results are beneficial for transport planners and transport authorities to develop appropriate transport planning strategies.

Urban Railway Development in Hanoi and the Possible Impacts on Mode Shifting: Experiences from Young Transport Users

This study aims to explore the travel behaviour of young travel group to understand different factors that could influence their mode choices, and their willingness to shift to the first urban railway line in Hanoi. This will help notify a range of measures that could be considered to decrease motorcycle usage and facilitate mode shift to public transport system. With the data collected from 396 students in five universities in Hanoi, Vietnam, a conditional logit regression model was developed to explore individual and alternative specific variables influencing the mode choice for studying trips. Key findings show that current mode usage, especially the dominant of motorcycle riding, having a strong effect on the tentative choice of Cat Linh – Ha Dong railway as a means of travelling to universities. Research results are beneficial for transport planners and transport authorities to develop appropriate transport planning strategies.

Urban Railway Development in Hanoi and the Possible Impacts on Mode Shifting: Experiences from Young Transport Users

This study aims to explore the travel behaviour of young travel group to understand different factors that could influence their mode choices, and their willingness to shift to the first urban railway line in Hanoi. This will help notify a range of measures that could be considered to decrease motorcycle usage and facilitate mode shift to public transport system. With the data collected from 396 students in five universities in Hanoi, Vietnam, a conditional logit regression model was developed to explore individual and alternative specific variables influencing the mode choice for studying trips. Key findings show that current mode usage, especially the dominant of motorcycle riding, having a strong effect on the tentative choice of Cat Linh – Ha Dong railway as a means of travelling to universities. Research results are beneficial for transport planners and transport authorities to develop appropriate transport planning strategies.

Research on Simulation Calculation of the Safety of Tight-Lock Coupler Curve Coupling

Once a train breaks down on a busy railway line, it will affect the whole traffic network. However, when a rescue locomotive is hooked up to the broken train for towing it to the next station, it is common that coupling dislocation occurs, which results in damages to couplers and the driver’s cab. To ensure the safety of the trains during the coupling, it becomes crucial to determine whether they can be linked safely and automatically under different line conditions. In this paper, position and pose of the rescue locomotive and the broken train on the line are calculated by geometric analytical calculation method, which determines the position relation of their couplers. Then a so-called “coupling characteristic triangle” was proposed to determine whether trains can be safely and automatically linked on the railway line. The triangles are constructed by the peak points of the couplers head of the front vehicle and the rear one and border lines of secure coupling area on the couplers. By judging the shape of the triangle, it can directly judge whether their couplers can be connected successfully. The method has been applied to check the safety of the trains during coupling on the Nanchang urban railway Line 4. The results show that the maximum swing angle of the coupler reaches 17.3957° in the straight–curve section with a radius of 325 m. At this time, coupling is most difficult, and trains need to be connected manually through the tractor; all the calculation results are verified in the actual line. By comparing different calculation methods for judging coupling safety, it is shown that the method proposed in this paper is accurate, efficient, and users can judge coupling safety more intuitively.

A Two-Step Method for Energy-Efficient Train Operation, Timetabling, and Onboard Energy Storage Device Management

This article proposes a novel two-step approach to concurrently optimize the train operation, timetable, and energy management strategy of the onboard energy storage device (OESD) to minimize the net energy consumption for a whole urban railway line. In Step 1, approximating functions representing the minimum net energy consumption of each specific interstation operation is obtained by data fitting based on the previous research outcomes. In Step 2, the optimal running time, initial state of energy (ISOE) of OESD, train speed profiles, discharge/charge management of the OESD during each interstation journey and at each station are obtained by applying convex optimization formulated by approximating functions gained in Step 1. The method is first tested with several general train cases to show its robustness and adaptability. Then, a real-world case based on Beijing metro Yizhuang line is studied and the optimal solution is found to reduce the net energy consumption 1.04%, 2.09%, and 23.77% for a service cycle of a single train when compared to other operation scenarios, i.e., fully charged, no management, and no OESD scenario, respectively. The approach is also computationally efficient with a computational time less than 1 min, namely 38.86 s for the upline and 48.38 s for the downline, spent on finding the optimal solution.

A numerical investigation of the impact of shield machine’s operation parameters on the settlements above twin stacked tunnels - A case study of Ho Chi Minh urban railway Line 1

Three-dimensional finite difference calculations are proposed to investigate the influence of operation parameters of the shield machines during twin stacked tunnel excavation on the surface settlements. The numerical model is validated by experimental data obtained from Hochiminh’s metro line 1 project, used as a reference case in this study. The parametric study focuses on the influence of the face support pressure, the grouting pressure, and the shield’s length. The numerical results indicated that a decrease does not always follow an increase in surface settlements' face and grouting pressure. A shorter shield machine causes smaller surface settlements to develop over single lower and twin stacked tunnels.

Design of indicators to guide capacity improvements in urban railway lines

The transport capacity of an urban railway line can be increased in many different ways. For planners and infrastructure managers it is vital to have all the tools available that allow choosing the most cost-effective solution among all the possibilities. This selection process can be complex sometimes and deciding how the available capacity should be increased is an important decision with significant financial consequences.In this paper new transport capacity indicators suitable for urban lines are presented; that can be used as a guide by decision-makers to help them decide on infrastructure capacity improvements. The indicators ease the process of deciding among different alternatives by considering the specific capacity improvement they involve individually.The model uses a railway simulator that allows obtaining the minimum departure-arrival itinerary times in the station under study. It has been applied to a case study in a suburban commuter line in Barcelona. Specifically, to the station of Provença that is a station with long Dwell Times during rush hour and belonging to the Spanish railway operator FGC.This case demonstrates the indicators application and contributions; it also shows that it would be possible to extend the same kind of study to other nodes allowing the systematization of their capacity improvement by fine-tuning their signaling system.

Investigation on railway investment-induced neighborhood change and local spatial spillover effects in Nagoya, Japan

Previous studies have proven the significant causal relationship between railway investment and gentrification in some cities. However, most of them have focused on the gentry and less on the effect on other social classes. To observe how railway investment affects neighborhood change for different population types, this study investigated the investment effects of two urban railway lines separately on the neighborhood change of the gentry, older population, and students in Nagoya, Japan. These two railway lines consisting of a subway and an elevated railway opened in the same year and were located in different areas of the city. Moreover, the spatial autocorrelation in panel data was considered to investigate possible local spillover effects. Finally, we observed that the railway investments in highly urbanized areas were more likely to induce gentrification. In addition, railway investment has some significant treatment effects on students compared to the older population.