In order to elucidate the mechanism of snow-falling from railway vehicles in winter, a mathematical model was studied to estimate the time taken for snow to fall from a railway vehicle in a warm tunnel. In addition, to validate the model which is based on the heat balance of snow accretion, snow falling experiments were carried out in a low-temperature room. Then the onset time of snow-falling was compared between the model and the results of the experiments. The result showed that it was possible to estimate the onset time of snow-falling, by setting an appropriate influence melting height on snow accretion at the interface between the metal plate and the snow accretion in the model.

We are developing an autonomous train operation system that allows trains to operate automatically while controlling wayside equipment based on the condition of the vehicle and wayside equipment. Autonomous train operation not only controls the acceleration and deceleration of trains, achieved through automatic operation, but also automatically makes operational decisions on board. We have developed the railway dynamic map as an information infrastructure for collecting and sharing onboard and wayside condition information needed for operational decision making and for risk assessment. This paper provides an overview of condition information management and risk assessment using the railway dynamic map.

RC beam-to-column joints in railway viaducts are designed to satisfy structural details. However, when overcrowded reinforcement arrangement measures are implemented at joints or high strength rebars are applied to members, a relationship between details of reinforcement arrangement and capacity of joint is required. In this study, we carried out cyclic loading tests and 3D FEM analyses to clarify this relationship. The results show that as the inside radius of the bend of longitudinal rebars decreases, the capacity of a joint decreases due to the reduction of compressive strut width, and that the ties in the joint have little effect on the capacity, although it increases the deformation performance.

This study proposed a new method capable of predicting the rail temperature distribution in nighttime at intervals of about 1 m by modeling the radiant heat of rail in detail using digital surface model (DSM) and meteorological data. To verify its prediction accuracy, the distribution of rail temperature and radiant heat were measured on a real track. As a result, the minimum rail temperature was about 2°C higher at the measurement points near buildings compared with that at other points due to strong radiant heat. We also confirmed that the proposed method can accurately reproduce the actual rail temperature distribution in nighttime.

Authors have proposed a seismic control device with a bridge collapse prevention function installable in narrow spaces. In this paper, we introduce a method for designing the proposed device. Specifically, we organized the results of the nonlinear response analysis of a single degree of freedom system and proposed a nomogram that can be used to calculate the displacement of the girders and the response ductility factor of the piers in accordance with equipment specifications. By using this method, it is possible to have a rough idea of the specifications to meet the required performance before detailed dynamic analysis is carried out.

Volcanic ash fall can seriously affect railway operations by causing problems such as track circuit shunting malfunctions and decrease in insulation performance of insulators. In this study, we experimentally investigated volcanic ash conditions that cause these problems. Results allowed us to clarify that 0.05 mm thick volcanic ash causes shunting malfunction, and that 1.2 mm thick volcanic ash containing saline water causes insulator flashover. Based on these results, we propose preventive actions which railway companies can implement to mitigate the effects of ash fall, using public information on eruptions.

As a basic technology for realizing autonomous train operation, we propose two functions: a function for creating a running profile on board a train and a function for creating a running profile on board to recover from delays caused by hazards. Running profiles are generated based on information such as timetables. The function for direct control of ground equipment from a train is designed to allow on-board equipment to set train routes, control turnouts on that route, and control level crossing warnings as trains approach.

In the case of ballasted tracks, track irregularity and rail surface roughness gradually increase due to repeated loadings from passing trains. Ballast tamping and rail grinding are carried out to repair these problems as part of general maintenance work. This paper verifies the effect of combining these two types of track maintenance to reduce the speed of track deterioration. Furthermore, extending the previously developed combined maintenance planning system, the authors simulate maintenance plans considering the effect of combined maintenance.

Developing sensing technology that can reliably detect obstacles on the track well ahead of a train is essential for advancing on-train forward-facing track monitoring. Therefore, we developed a method for detecting obstacles in front of trains using cameras and sensors. In our method, obstacles such as people and vehicles are detected by combining multiple sensors within a detection area around the tracks. In this paper, we report on the results of a study of sensor configurations suitable for obstacle detection, the detail of our detection algorithm using cameras and LiDARs or a stereo camera, and the results of detection performance evaluation according to distance between train cab and object.

There are many sources of railway vehicle noise generated by equipment such as gear devices installed in the narrow space of a bogie frame under the floor of a vehicle. Therefore, it is difficult to separate the sound sources onboard a vehicle with a sound level meter, and up to now there no method has been developed for separating the sound sources. As a method to solve this problem, we are working on applying a sound source visualization method to the noise measurement of railway driving devices. The 4-channel beamforming method (BF method) and the envelope intensity method (EI method) are used as sound visualization methods, and the test results are compared. This paper reports on the results of noise measurement on a driving device using a sound source visualization method in bench-scale testing, and the results of a study to improve accuracy. We confirmed that the beamforming method has excellent imaging stability for transient sounds, and that image processing using multiple small microphone arrays improves the imaging accuracy of the BF method.

We numerically investigated the aerodynamic characteristics of pantographs for conventional trains in a crosswind by using large-eddy simulations (LESs). Although previous experimental study revealed that the lift force increases significantly under crosswind conditions, the mechanisms underlying this phenomenon have not been clarified. Therefore, the flow fields around the pantograph head were carefully investigated by LESs. It was found that there are two main mechanisms: one is a steady large-scale vortex generated on the upper surface of the pantograph head, and the other is a pressure increase on the lower surface of the pantograph head. In addition, LESs were carried out using modified pantograph head shapes to investigate methods for reducing the lift force on the pantograph head taking into account the mechanisms above. As a result, a maximum lift reduction rate of approximately 60% was achieved, indicating that an effective lift force reduction method was proposed.

In this paper, setting and testing methods for deformation characteristics of soils for a dynamic ground response analysis were studied. First, we proposed a parameter setting method using an optimization technique and it was confirmed that the proposed method could be used to set the parameters more accurately than three designers with different experience. Second, deformation characteristics tests with some cyclic numbers were carried out. The result showed that a slight difference in cyclic numbers causes quite large differences in the shear stiffness in large strain levels. In addition, a series of ground response analyses was carried out using the above-mentioned parameter-setting method with some test results. The results showed that differences in the number of cycles at each strain level may affect the results of the dynamic ground response analysis. Moreover, it was also confirmed that by using the shear stiffness obtained from monotonic loading test results we can accurately evaluate the dynamic response of the surface ground observed in the hybrid dynamic ground response analysis and simulate real soil behavior.