Properties of train traffic flow in moving block system

The development direction of railway is to improve the capacity and the service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running process of train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow (including capacity and average speed) are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increasing of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block.     

Urban rail departure capacity analysis based on a cellular automaton model

As an important traffic mode, urban rail transit is constantly developing toward improvement in service capacity and quality. When an urban rail transit system is evaluated in terms of its service capacity, the train departure capacity is an important index that can objectively reflect the service level of an urban rail transit facility. In light of the existing cellular automaton models, this paper proposes a suitable cellular automaton model to analyze the train departure capacity of urban rail transit under different variable factors and conditions. The established model can demonstrate the train operating processes by implementing the proposed sound rules, including the rules of train departure at the origin and intermediate stations, and the velocity and position updating rules. The properties of train traffic are analyzed via numerical experiments.The numerical results show that the departure capacity is negatively affected by the train departure control manner. In addition,(i) the real-time signal control can offer a higher train service frequency;(ii) the departure capacity gradually rises with the decrease in the line design speed to a limited extent;(iii) the departure capacity decreases with extension in the train length;(iv) the number of departed trains decreases as the train stop time increases;(v) the departure capacity is not affected by the section length. However, the longer the length, the worse the service quality of the urban rail transit line.The experiments show that the proposed cellular automaton model can be used to analyze the train service capacity of an urban rail transit system by performing quantitative analysis under various considered factors, conditions, and management modes.     

Scheduling of high-speed rail traffic based on discrete-time movement model

In this paper, a new simulation approach for solving the mixed train scheduling problem on the high-speed double-track rail line is presented. Based on the discrete-time movement model, we propose control strategies for mixed train movement with different speeds on a high-speed double-track rail line, including braking strategy, priority rule, travelling strategy, and departing rule. A new detailed algorithm is also presented based on the proposed control strategies for mixed train movement. Moreover, we analyze the dynamic properties of rail traffic flow on a high-speed rail line. Using our proposed method, we can effectively simulate the mixed train schedule on a rail line. The numerical results demonstrate that an appropriate decrease of the departure interval can enhance the capacity, and a suitable increase of the distance between two adjacent stations can enhance the average speed. Meanwhile, the capacity and the average speed will be increased by appropriately enhancing the ratio of faster train number to slower train number from 1.     

网络条件下列车追踪模型及延迟传播的研究

描述了一种移动闭塞下考虑不同类型列车混跑时基于元胞自动机的列车追踪模型.将该模型应用到铁路网，模拟了网络条件下列车运行情况.应用该模型模拟了移动闭塞下列车延迟传播的现象.分析了发车间隔松弛时间、初始延迟时间等因素对列车延迟的影响.将该模型的模拟结果和理论公式的计算结果进行了比较，验证了模型的可靠性和有效性. 关键词： 元胞自动机 铁路网络 列车追踪模型 移动闭塞     

Modeling and Simulation for Urban Rail Traffic Problem Based on Cellular Automata

Based on the Nagel-Schreckenberg model, we propose a new cellular automata model to simulate the urban rail traffic flow under moving block system and present a new minimum instantaneous distance formula under pure moving block. We also analyze the characteristics of the urban rail traffic flow under the influence of train density, station dwell times, the length of train, and the train velocity. Train delays can be decreased effectively through flexible departure intervals according to the preceding train type before its departure. The results demonstrate that a suitable adjustment of the current train velocity based on the following train velocity can greatly shorten the minimum departure intervals and then increase the capacity of rail transit.     

Modeling and Simulation for Urban Rail Traffic Problem Based on Cellular Automata

Based on the Nagel-Schreckenberg model, we propose a new cellular automata model to simulate the urban rail traffic flow under moving block system and present a new minimum instantaneous distance formula under pure moving block. We also analyze the characteristics of the urban rail traffic flow under the influence of train density, station dwell times, the length of train, and the train velocity. Train delays can be decreased effectively through flexible departure intervals according to the preceding train type before its departure. The results demonstrate that a suitable adjustment of the current train velocity based on the following train velocity can greatly shorten the minimum departure intervals and then increase the capacity of rail transit.     

Empirical analysis of dependence between stations in Chinese railway network

A railway transportation system can be represented by a bipartite network consisting of trains and stations, where a train is connected to all stations where it stops. In this paper, motivated by the resource-allocation process taking place on networks, we design a method to project a Chinese train-station bipartite network into a weighted station network. A new metric is proposed to quantify the dependence between pairs of stations, which is shown to follow a shifted power-law distribution. In addition, we compare the resource-allocation method and the well-known multiple-edge method, and the results indicate that our proposed method is more reasonable.     

Scheduling trains on railway network using random walk method

According to random walk, in this paper, we propose a new traffic model for scheduling trains on a railway network. In the proposed method, using some iteration rules for walkers, the departure and the arrival times of trains at each station are determined. We test the proposed method on an assumed railway network. The numerical simulations and the analytical results demonstrate that the proposed method provides an effective tool for scheduling trains. Some characteristic behaviours of train movement can be reproduced, such as train delay.     

Ground vibrations from heavy freight trains

Ground vibration from heavy freight trains on good quality welded track are found to have only a weak dependence on train speed above 30 km/h. At the site on which these tests were carried out a critical speed was found at which the vibration reached a peak. The frequencies of vibration produced appear to be functions of track and vehicle dimensions and the critical speed occurs at the coincidence of sleeper passage frequency and the total vehicle on track resonance frequency.     

The relationship between energy consumption and train delay in railway traffic

Based on deterministic NaSch model, we propose a new cellular automation model for simulating train movement. In the proposed model, the reaction time of driver/train equipment is considered. Our study is focused on the additional energy consumption arising by train delay around a traffic bottle (station). The simulation results demonstrate that the proposed model is suitable for simulating the train movement under high speed condition. Further, we discuss the relationship between the additional energy consumption and some factors which affect the formation of train delay, such as the maximum speed of trains and the station dwell time etc.     

An Improved Discrete-Time Model for Heterogeneous High-Speed Train Traffic Flow

This paper aims to present a simulation model for heterogeneous high-speed train traffic Row based on an improved discrete-time model(IDTM).In the proposed simulation model,four train control strategies,including departing strategy,traveling strategy,braking strategy,overtaking strategy,are well defined to optimize train movements.Based on the proposed simulation model,some characteristics of train traffic Bow are investigated.Numerical results indicate that the departure time intervals,the station dwell time,the section length,and the ratio of fast trains have different influence on traffic capacity and train average velocity.The results can provide some theoretical support for the strategy making of railway departments.     

Acoustic localization scheme and accuracy analysis for underwater vertical moving target using seabed stations

To measure the trajectory of an underwater vertical moving target(UVMT) in transient motion with high accuracy and high frame rate,an acoustic localization model using seabed stations with an acoustic beacon was presented.A solution algorithm based on the Gauss-Newton method was derived,which was shown to satisfy the local linear convergence.Accuracy analysis of the numerical simulation indicated that the station location,sound velocity,and signal time delay estimation errors were propagated to location parameters through measurement ranges,and the main affecting factors included the station geometry,target relative location,and acoustic conditions.Vertical accuracy was improved using a supplemental surface station coupled with the seabed stations.Detailed characteristics were indicated by accuracy distribution from the full test sea area.A 14-station array composed of 13 seabed stations and 1 surface station in a test sea of 1 km x 1 km and 60 m in depth demonstrated that the average root mean square errors(RMSEs) in the x,y,and z directions were 0.30,1.47,and0.34 m,respectively,in the vertical range of 35-60 m.This work provided a technical approach for UVMT localization,which would be useful for designing related measurement systems.     

DYNAMIC STABILITY OF TRAINS MOVING OVER BRIDGES SHAKEN BY EARTHQUAKES

The dynamic stability of trains moving over bridges shaken by earthquakes is studied. Unlike the seismic analysis of structures containing a single subsystem, the seismic analysis of a bridge sustaining a passing train requires not only information on acceleration, but also on velocity and displacement of the ground motion. Four typical earthquakes, including the 1999 Chi-Chi Earthquake, were adopted as the input excitations, each of which was normalized to have a moderate intensity. The results indicate that a train initially resting on the bridge can stay safely under the ground motions considered, if the bridge and track structures do not exhibit inelastic deformations during the earthquake. The type of the vertical component of ground motions can affect significantly the stability of the train-rail- bridge system. As a preliminary attempt, safety, possible instability and instability regions were established in a three-phase plot for the train running over the bridge for each of the earthquakes considered, from which the maximum allowable speed for the train to run safely under the specified ground acceleration can be obtained.     

An Improved Walk Model for Train Movement on Railway Network

In this paper, we propose an improved walk model for simulating the train movement on railway network. In the proposed method, walkers represent trains. The improved walk model is a kind of the network-based simulation analysis model. Using some management rules for walker movement, walker can dynamically determine its departure and arrival times at stations. In order to test the proposed method, we simulate the train movement on a part of railway network. The numerical simulation and analytical results demonstrate that the improved model is an effective tool for simulating the train movement on railway network. Moreover, it can well capture the characteristic behaviors of train scheduling in railway traffic.     

Dynamic interaction analysis of trains moving on embankments during earthquakes

This study developed a time-domain finite element method to simulate the derailment of trains moving on embankments under seismic loading. The finite element mesh included trains, rails, embankment foundation, soil, and the absorbing boundary condition, where the seismic displacements were applied at the bottom of the mesh. For the cases of a perfectly smooth rail with or without seismic loading, the train derailment coefficients are almost independent of train speeds. However, with minor rail irregularities, they are highly dependent on train speeds. This study also shows that the resonance between the train and earthquake plays an important role in train derailment. The maximum derailment coefficients are quite linear in proportion to the peak ground acceleration (PGA) of the earthquake, if the structural behaviors and dynamic soil properties are not nonlinear.     

Suspended bridges subjected to moving loads and support motions due to earthquake

The paper deals with the vibration of suspended bridges subjected to the simultaneous action of moving loads and vertical support motions due to earthquake. The basic partial integro-differential equation is applied to the vertical vibration of a suspended beam. The dynamic actions of traffic loads are modelled as a row of equidistant moving forces, while the earthquake is considered by vertical motions of supports. The governing equation is solved first analytically to receive an ordinary differential equation and next numerically. Moreover, the designed world's largest suspended bridge—Messina Bridge—is investigated (central span of length 3.3 km). The paper studies the effect of various lags of the earthquake arrival because the earthquake may appear at any time when the train moves along a large-span bridge. The modified Kobe earthquake records have been applied to calculations. The results indicate that the interaction of both the moving and seismic forces may substantially amplify the response of long-span suspended bridges in the vicinity of the supports and increase with the rising speed of trains.     

The effect of critically moving loads on the vibrations of soft soils and isolated railway tracks

The dynamic response of the railway track is strongly influenced by the underlying soil. For a soft soil and very high train speeds or for a very soft soil and regular train speeds, the train speed can be close to the speed of elastic waves in the soil. This paper presents a detailed study of the so-called “moving-load effect”, i.e. an amplification of the dynamic response due to the load movement, for the tracks on soft soil. The analysis is carried out by evaluating the related integrals in the wavenumber domain. The influence of the load speed is quantified for a large set of parameters, showing that the effect on the soil vibration is reduced with increase of the frequency, track width and inverse wave velocity. Therefore, the moving-load effect associated with vibratory train loads is negligible whereas the amplification associated with the moving dead weight of the train can be significant. The strong moving-load effect on a perfectly homogeneous soil, however, can be strongly diminished by a layered or randomly varying soil situation. This theoretical result is affirmed by measurements at a test site in Germany where the trains run on a very soft soil at a near-critical speed. The results for soft soils are compared with experimental and theoretical results for a stiff soil. It is found that the influence of the stiffness of the soil is much stronger than the moving-load effect. This holds for the soil vibration as well as for the track vibration which both show a minor dependence on the load speed but a considerable dependence on the soil stiffness in theory and experiment.Railway tracks can include soft isolation elements such as rail pads, sleeper shoes and ballast mats. For these types of isolation elements and normal soil conditions, the influence of the load speed is usually negligible. There is only one isolation measure for which the moving load may be effective: a track which is constructed as a heavy mass-spring system. The resonance of this track system is shifted to lower frequencies and amplitudes for increasing train speed. A critical train speed can be reached if the mass-spring system has a marginal bending stiffness along the track.     

Change of acoustic characteristics caused by platform screen doors in train stations

Railway companies are encouraged to install platform screen doors (PSDs) for safety reason in Japan. The PSDs might affect train noises in stations, but the effects are not well understood. The aim of the present study is to clarify the effects of PSDs on acoustic characteristics. PSDs can be principally classified by two types, i.e., mobile full-height (MFH) and mobile half-height (MHH). Train noises were recorded in ground and underground train stations with MFH, MHH and without PSDs. The noises were evaluated by noise level, the maximum peak of the interaural cross-correlation function (IACC), and the width of the first decay (W_Φ(0)) of the autocorrelation function. Noise level emitted by trains was reduced by PSDs in both aboveground and underground stations. IACC was decreased by PSDs in both ground and underground stations, suggesting that PSDs made train noises more diffused. W_Φ(0) was decreased by PSDs in both ground and underground stations, which means that the train noises in station with PSDs have higher spectral centroid, suggesting that the PSDs blocked the lower frequency components of train noises.     

高温超导高速磁浮交通系统悬浮导向与牵引方案研究

本文提出了一种全高温超导高速磁悬浮交通技术模式, 该技术模式采用高温超导钉扎悬浮导向和高温超导直线电机牵引, 具有高速运行、 静态悬浮和动态自稳定悬浮导向三大特征. 根据5 编组时速500 公里磁悬浮列车的运行要求和工况, 本文对高温超导钉扎悬浮导向系统和高温超导直线牵引系统进行了方案设计, 并通过有限元仿真对所提方案进行了可行性分析和验证. 结果证明了全高温超导磁悬浮系统的高速运行、 静态悬浮和动态自稳定悬浮导向技术优势和设计方案的可行性.     

Dynamic analysis of a coupled high-speed train and bridge system subjected to collision load

A dynamic analysis model is established for a coupled high-speed train and bridge system subjected to collision-load. A 7×32 m simply-supported high-speed railway bridge with box girders is considered as an illustrating case study. A high-speed China-Star train is traveling on the bridge. The time history curve of a drifting-floe collision force is obtained from a field experiment and introduced as the excitation load on the bridge piers. Then, the dynamic response of the coupled train–bridge system subjected to the measured drifting-floe collision is calculated. Afterwards, the running safety indices such as derailment factor, offload factor and lateral wheel-rail force of train vehicles are investigated. The results show that the dynamic response of the bridge subjected to a collision load is much greater than the one without a collision, resulting in a big influence on the running safety of high-speed trains. For the case study, a critical train speed curve is proposed to evaluate the running safety of train vehicles on the bridge under drifting-floe collision with various intensities.