Carbon neutrality is a necessary goal as a countermeasure against climate change. Therefore, it has become more important to promote further energy saving and the use of energy storage systems in railway systems. Notwithstanding, falls in passenger traffic due to COVID-19 have had a significant impact on railway management, and reducing infrastructure maintenance costs has become an urgent issue. This paper presents recent research and development on power supply systems, especially for decarbonizing the railways and reducing resources required for maintenance of overhead contact line systems.

The spread of new coronavirus infections (hereinafter referred to as COVID-19), which began in Japan at the end of 2019, has greatly affected railway business. There is an urgent need to reduce fixed costs while responding to changing needs for mobility in a post COVID-19 society. As such it is necessary to speed up research and development so that it can contribute to helping railway companies reduce fixed costs. This paper first introduces an overall picture of research and development related to the sophistication of automatic operation and its application to conventional railway lines. Secondly, it introduces ongoing research and development efforts related to the utilization of non-failsafe processors or a public communication network such as 5th Generation mobile communication systems (5G) for critical applications in the railway field. Finally, it presents the direction and policy of future research and development for equipment saving and cost reduction.

Materials used in the railway system are required to maintain a designated performance over a predetermined period of time. Management of changes in these materials over time is therefore very important. Our current research focuses mainly on materials with a long serviceable life such as concrete and steel structures, and friction members such as rails, wheels, bearings, brake shoes, contact wires, and pantograph contact strips. We are also developing new materials or new technologies for the railway system. This paper outlines recent research and development activities in and the future outlook for materials technology.

Traditionally, the design and maintenance of electric power facilities of electric railways in bay areas have been carried out according to a uniform classification of pollution based on distance from the coast and other factors. In order to improve the safety of these facilities and save labor for maintenance, it is necessary to subdivide this uniform classification according to the actual pollution situation. Therefore, we propose a method for estimating the Equivalent Salt Deposit Density on insulator surfaces at any point on an open section using meteorological and topographical information provided by public institutions.

In Japan, in order to prevent supports (referred to poles and portal structure etc.) in overhead contact systems from collapsing at the time of an earthquake, we design them according to the Seismic Design Guideline for Overhead Contact Systems and Commentary (hereafter referred to as the OCS Guideline). We revised the OCS Guideline in 2013 to evaluate seismic performance of supports more precisely. The paper shows the process of revising OCS Guideline until now and details of the latest revision of the OCS Guideline.

A high voltage DC feeding system, which consists of higher-voltage feeders and DC-DC converters in addition to an existing feeding circuit, is assumed to improve the performance of power supply to trains without changing the nominal voltage of contact lines and onboard traction systems. In this system, the method for controlling the converter is an important element which must be taken into consideration to maximize energy savings. In this paper, we propose a converter control method to make the voltage ratio constant between the contact line and the higher-voltage feeder. In this paper, the high voltage DC feeding system with this converter control method is called a "DC-AT feeding system." We evaluated the energy savings of this system through simulation, and case studies on a model line confirmed that this system can reduce energy consumption by 4.5% at most, and on average 3.5%, compared to conventional DC feeding systems.

Recently, the importance of obstacle detection methods for railway has been increasing. In the field of automobiles, obstacle detection systems with sensors have been introduced on mass-produced vehicles. However, in railway, a practical detection system does not exist because railways require longer detection distances than do automobiles. Therefore, we have developed a train frontal obstacle detection method using a camera and LiDAR. We confirmed that our method detects a person 200 m away, which a camera alone cannot detect, with 45% accuracy at night.

ATO (Automatic Train Operation) systems which are equipment for automated driving control under protection of ATC (Automatic Train Control), continuous type of ATP, is introduced in specific types of line, such as AGT (Automated Guideway Transit ) systems or subway systems in Japan. There is a growing need for new type ATO system which is operated by a staff who is not required driver's license in order to reduce operating costs further. We have developed an ATO system based on ATS (Automatic Train Stop) -DK which is intermittent type ATP and equipped continuous speed check. In this paper, we show the concept of the ATS-based ATO system and report on the specifications of this system and functional field test results.

The tongue rail opening force of a turnout is measured to indirectly estimate the fixing force of a turnout. Although tongue rail opening force is known to be proportional to the fixing force, it is also known that the proportional relationship sometimes does not hold. This non-proportionality can lead to mis-estimation of the fixing force, in turn causing malfunction of the switch due to the high fixing force. In order to solve this problem, we clarified the mechanism and causes of the mis-estimation related to contact between rails. The results of field investigations and motion simulation using a flexible multibody model of switch, were used to developed maintenance methods and a measurement tool for avoiding mis-estimation.

Most frictional materials used in railways are made of composite material, and their macroscopic material properties are largely affected by their microscopic structure. It is useful to clarify the relationship between microscopic structure and material properties by numerical simulation for effective improvement or development of the materials. In this study, we developed an image-based microscopic model by using X-ray computed tomography for a metalized carbon pantograph contact strip material and evaluated its Young's modulus, thermal conductivity and electrical resistivity based on the homogenization method. The calculated material properties were more consistent with the experimentally measured values than the estimated values based on the classical Voigt model. We also introduce the analysis result of the stress, temperature and current density distribution in the microscopic model.

The cross sectional repair of concrete structures is carried out for the purpose of restoring or improving durability. However, some re-deterioration, such as corrosion of reinforcing bars, floating of repair materials, or peeling, has been observed. Such re-deterioration is considered to be due to deterioration factors such as water that has permeated the repair area. In this paper, we report the result of non-destructive visualization of the moisture behavior of the repair area using a neutron beam tester.

Tapered roller bearings are mainly used in rotating parts of gear units on railway vehicles. In order to prevent bearing seizure and to improve gear unit reliability, it is important to ensure appropriate clearance between bearings. Bearing clearance changes from its initial value as vehicles travel due to atmospheric temperatures and variation in the initial values in the gear unit assembly, which affects bearing performance. In this research, an actual gear unit was subjected to bench rotation tests under various bearing clearances and various atmospheric temperatures. Bearing temperature and torque were measured, and changes in bearing clearance were estimated.