Narrow Results

In this paper we consider the location of stops along the edges of an already existing public transportation network. This can be the introduction of bus stops along some given bus routes, or of railway stations along the tracks in a railway network.

The positive effect of new stops is given by the better access of the potential customers to public transportation, while the travel time increases due to the additional stopping activities of the trains. The latter leads to a negative effect for the customers. The goal is to cover all given demand points with a minimal amount of additional traveling time, where covering may be defined with respect to an arbitrary norm or gauge. This problem is NP-hard, even in the special case of Euclidean distances. In this paper, we derive a finite candidate set leading to a discrete set covering problem. Moreover, we identify network structures in which the coefficient matrix of the resulting set covering problem is totally unimodular, such that the problem can be solved efficiently in this case. Extensions of the problem are also discussed.

This study investigated railway line planning optimization models that determine the frequency of trains on each line to satisfy passenger origin–destination demands while minimizing related costs. Most line planning models assume that all trains on the same route run with the same halting pattern. However, to minimize passenger travel time and to provide a train service with faster travel times to as many stations as possible, we must consider various halting patterns; these patterns can be provided in advance or are required to be formulated. Our study addresses two line planning problems that consider halting patterns, describes the computational complexities of each problem, and presents the column generation approach for one model. We also present experimental results obtained for the Korean high-speed railway network.

In order to clarify the cracking and failure behavior of gray cast iron brake blocks that are used for the railway applications, macro- and micro observations regarding the cracks and the micro-structure of the used brake blocks were examined. Three brake blocks, which have different degrees of hot spots and cracking during the actual application, were selected for testing. In addition, a thermal-mechanical coupled finite element analysis (FEA) was applied to calculate the temperature and the stress field in the brake blocks during braking. As a result, it was observed that surface cracks were initiated at the hot spots and propagated into the matrix. From the observation of dispersed graphites close to the crack path, it can be said that the deterioration of materials due to the frictional heat of braking made it easy to initiate cracks at the hot spot. The hardness of the brake block was recommended to be under 85 by the Rockwell B scale in order to prevent hot spots and crack initiation. From the FEA, the procedure for the occurrence of hot spots and cracks was successfully simulated by assuming the surface roughness on the slid surface of the brake block.

In general railway infrastructure operates in a complex and non homogeneous environment where low power electronics has to function in the similar environment as large voltages and currents from the trains. The environment close to the railway tracks is heavily polluted by electromagnetic (EM) noise from the railway systems itself. The reliability of the railway signalling-, communication-, and control system depends on the degree of isolation from EM noise. It is important to observe the real system and its characteristics in real situation. The complexity of the infrastructure is not easy to simulate or calculate, and therefore measurements were performed on real system in operation. A large number of measurements were made on site at signalling systems and installations of Banverket (the Swedish Rail Administration). By studying and analyzing these measurements, the extent of EMI (Electromagnetic interferences) -related faults can be estimated. In situ measurements must be performed on systems that have obvious problems show increasingly fast and high transients in a DC signalling subsystem. The statistics also show an increased activity of transients during a period before a certain circuit in this system gets out of order. The presented results clearly show how the electromagnets interference effects he signalling system in a signalling box. The measurements in this case study have provided new information on a railway subsystem and have revealed frequencies that are difficult to explain at this moment.

There has been a growing interest to carry out the vehicle–track–bridge (VTB) dynamic interaction analysis using 2D or 3D finite elements based on simplified wheel–rail relationships. The simplified or elastic wheel–rail contact relationships, however, cannot consider the lateral contact forces and geometric shapes of the wheel and rails, and even the occasional jump of wheels from the rails. This does not guarantee a reliable analysis for the safety running of trains over bridges. To consider the wheel–rail constraint and contact forces, this paper proposes a versatile 3D VTB element, consisting of a vehicle, eight rail beam elements, four bridge beam elements, and continuous springs as well as the dampers between the rail and bridge girder. With the 3D VTB element matrices formulated, a procedure for assembling the interaction matrices of the 3D VTB element is presented based on the virtual work principle. The global equations of motion of the VTB interaction system are established accordingly, which can be solved by time integration methods to obtain the dynamic responses of the vehicle, track and bridge, as well as the stability and safety indices of the moving train. Finally, an illustrative example is used to verify the proposed the versatile 3D VTB element for the dynamic interactive analysis of railway bridges under moving train loads.

Rail irregularities are the main factors influencing the ride comfort of trains moving over tracks. Despite various investigations made in this regard for the ballasted tracks, there is a lack of studies for the ballast-less tracks. This limitation is addressed in this study. To this end, a vehicle/slab-track interaction numerical model was developed, which was validated by comparison of the results obtained herein with those of the field tests carried out in this study. The effects of rail irregularities with various amplitudes and wavelengths on the ride comfort were studied by a comprehensive parametric analysis. Particularly, the effects of the wavelengths and amplitudes of rail irregularity on the ride comfort were investigated. Contrary to the current understanding, it was shown that rail irregularities with short wavelength have considerable effects on the ride comfort for the slab-tracks. In addition, the ride comfort decreases significantly when the wavelengths of rail irregularity become less than 0.75m in the metro lines. The critical speed of the train (at which the lowest ride comfort is obtained) was derived as a function of rail irregularity. The results obtained indicate that the amplitude of rail irregularity has negligible influence on the critical speed of the train.

Track is a key component in railway transportation systems. They are usually fixed by fasteners and supported by discrete sleepers, which sit on the ballast. A lot of research has been conducted to check the integrity of the rail track itself, like railway level and alignment; however, limited work has been carried out on the damages of railway supports including loosing and missing fasteners and damaged ballast. In this paper, the support–track–vehicle interaction system is analyzed in which the supports and track are modeled as evenly distributed springs and Euler beam, respectively, and the vehicle is simplified as a spring–mass system. It is found the natural frequencies of the interaction system change periodically with respect to the location of the vehicle, whereas the periodicity is broken when the support is damaged. Then, a detection method is proposed to identify the damaged supports by using the vertical acceleration of the traversing inspection vehicle, which acts as both the “exciter” and “message carrier” of the test. It shows good performance on the detection of damaged supports in both numerical and experimental validations. Moreover, it is more practical than other detection methods in real engineering applications because only one single accelerometer is required.

In this paper, a robust parallel finite-element/genetic-algorithm (FE/GA) procedure is presented for finding the optimal layout of wave barriers in the ground alongside the underground or above-ground railways. The proposed FE/GA procedure is capable of optimizing the topology of the wave barriers by altering the FE model geometry and mesh at each optimization step to cope with the excitations by underground, above-ground, and simultaneous under- and above-ground loadings. The results obtained show that this coupled procedure is effective for the analysis and design of different types of wave barriers subjected to dynamic transient loadings. Three different types of wave barriers are studied including wave impeding blocks (WIBs), jet-grouted columns, and trenches. It is found that the open trenches have the largest mitigation capacity and if they cannot be used, the WIBs perform better than the jet-grouted columns. Although the wave barriers can notably reduce the ground vibrations induced by underground trains, they perform more effectively when the source of vibrations is located at the ground surface.

In a railway track, the sleeper’s responses on a non-homogeneous foundation have been investigated by researchers focusing on the foundation behavior along the rails. However, the foundation can also vary along the sleeper length, particularly when the track is newly tamped. The foundation at the sleeper center is often weaker than those under the rails and this non-homogeneity directly affects the sleeper responses. This paper presents a new model to calculate the influence of such foundations on the dynamic responses of the railway sleepers. This model is developed by combining a finite element model for the sleepers and foundation and a model of periodically supported beams subjected to moving loads for the rails. In this paper, the foundation contains three parts with different mechanical behaviors. The sleeper’s responses can be calculated by transforming the finite-element dynamic stiffness matrix to the one considering the boundary conditions and the relation between the rail seat forces and rail displacements governed by the beam model. This method reduces all the degrees of freedom of the railway track to its one period which gives a substantial reduction in computational time. The numerical applications show that the more homogeneous (so-called consolidated) the foundation is, the larger the sleeper strain is at its center. This result shows the potential application of the sleeper responses to estimating the consolidation level of the foundation.

Environmental management systems (EMS) require performance evaluation of significant environmental aspects. Much has been published on how to achieve environmental performance evaluation but little information is available on applications in practice. The Swedish National Rail Administration, Banverket, initiated the implementation of EMS in 1998, at about the same time as many other rail administrations. In this paper an overview of the application of EMS at rail administrations in selected countries is presented and systems for environmental performance evaluation within the EMS used by Banverket are analysed. The use of EMS by rail administrations was found to vary from the absence of environmental management to fully implemented EMS, mainly ISO 14001. At Banverket, EMS is widely used but the environmental performance evaluation could be improved by introducing indicators and merging all types of environmental monitoring, currently reported separately, into a common system.

The preparedness and the emergency management against tsunami are an increasingly important issue for public transportation operators. The current state of these two is studied by conducting the hearing and questionnaire survey for domestic operators, in addition to the hearing by the national and local governments, focusing on actual actions taken against the 2010 Chile Earthquake Tsunami and the 2011 Tohoku Earthquake Tsunami. Critical issues are discussed in order to promote the preparedness against Tokai–Tonankai–Nankai Earthquake Tsunami which is likely to occur in the near future.

The Laos National Railway network is a milestone in the country’s transportation history. From the Chinese perspective, the China–Laos Economic Corridor (CLEC) is a vital sub-component of China’s Belt and Road Initiative (BRI). From the Laotian perspective, the Southeast Asian country intends to transform from a land-locked country (the only country within ASEAN or the Association of Southeast Asian Nations) into a land-linked country with Chinese equipment and infrastructure inputs. Through the railway system, Laos will be connected to maritime ports in China, Cambodia, Thailand and Vietnam, potentially benefiting its tourism industry, workforce mobility, land sales, services/retail outlets and intra- as well as extra-ASEAN trade and investments. Laos has proven to be the most politically stable, regime-reliable, perhaps complementary entity that has a stake in the success of the pan-Asian railway for the sake of its own economic development at the moment. At least, it does not require complicated diplomatic efforts, unlike the cases of Vietnam and Myanmar at this point of time. Thus, it may turn out to be a win–win situation for both the Laotians and the Chinese.

Pond ash is a suitable embankment material for the construction of road. However, this material is not in practice for the construction of railway embankment in India. Very limited basic study is available in the literature. Due to this, study the behavior of pond ash railway embankment under dynamic condition, a pilot project on 'Design of pond ash railway embankment' is carried out by Central Road Research Institute, New Delhi, India. Pond ash was collected from National Thermal Power, Kahalgaon, Bihar, India. In this paper, geotechnical properties of pond ash and local soil are presented. Design and stability analysis of embankment with different height (with or without berm) is carried out considering the uniformly distributed load due to train loading under the water logged and sudden drawdown conditions with earthquake factor. It was observed that critical factor of safety was found for lower height of embankment in comparison to the higher embankment.

In order to study the high speed railway vehicle carbody dynamic property and vibration control problems, 1/8 scaled carbody rig has been designed and manufactured. Firstly, the scaled test rig is built and performed an experimental modal test technology. Secondly, finite elements computational modal analysis has been carried out to determine the structural dynamics behavior of the realized model compared the field modal test results. Finally, the achieved results verify the predicted dense lying carbody eigenvalues frequencies between these two kinds of method. The accomplished experimental modal analysis provides a sophisticated basis to improve dynamic property of scaled carbody structure for vibration control. The results are shown that scaled carbody test rig design and modal analysis technology can be effectively used to predict objectively the carbody comfort and bending vibration.

This paper selects three transportation modes, including civil aviation, highways and waterways, to guide to the construction of railway safety warning system. The above three modes, which are similar to railway system in safety management, organization structure and safety management status, are introduced and compared firstly. Through the analysis of current warning system of the transportation methods we chose, we then provide the structure of safety early warning system of railway transportation.