By using the global positioning system (GPS), a novel train detection system has been established to assist trains with carbody tilt control. Japanese tilting trains can be equipped with an onboard database to store the current location and track conditions, thereby controlling the body tilt angle. This paper describes method to detect a train current position precisely by a combination of GPS and curvature collation, using the onboard database. This system was subjected to a running test to prove that its positional error was less than four meters.

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An ultrasonic testing technique was studied for a hollow axle with a 30 mm bore diameter manufactured on a trial basis for conventional railway vehicles. To compensate for the decrease in crack detection sensitivity due to the small bore diameter, a piezocomposite focal probe was designed. It has been demonstrated that the ultrasonic testing equipment thus developed could detect artificial flaws with a depth of 0.15 mm at the non-fitted central part and those with a depth of 0.3 mm at the inner end of the wheelseat (fitted part). The accuracy of axle inspection for conventional railway vehicles equipped with such hollow axles will match that of Shinkansen vehicles.

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Ventilated-type induction motors are widely used as traction motors on railway vehicles. However, they require overhauls for internal cleaning and are a major noise source. To solve these problems, we propose to use a totally enclosed permanent magnet synchronous motor as the traction motor, which has the same power-to-weight ratio as that of conventional ventilated type traction motors. This paper reports the results of temperature rise tests, noise measurement and energy consumption calculations. The results show that the noise level fell 10dB and energy consumption decreased by 10%.

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Feeders are installed as standard equipment on DC electrified railways in Japan in order to complement the electric capacity of contact wires. The feeder messenger catenary system, in which the messenger serves the function of a feeder, is now being increasingly adopted in metropolitan areas. Thus we have developed a new feeder messenger catenary system with an auxiliary wire so that the contact wire is hard to break. During system developments, we investigated the best structure for this purpose first and simulated its electric performance. Then, we performed running tests using a pantograph installed on RTRI's current collection testing equipment to evaluate the performance of the new system. The test results proved that there were no problems in its current collection performance up to 150kmh.

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High-voltage DC ground relays (64P) are commonly used at DC railway substations to detect DC feeding bus ground faults, which may cause fire or other serious damage. Therefore, 64P relays, which send a command to open all related circuit breakers, are very important devices. However, 64P relays sometimes disrupt railway traffic because they are occasionally activated by irrelevant faults, such as ground faults at external feeding lines or other substations. We are now developing a new method of detecting DC bus ground faults that can eliminate the influence of unrelated faults. This paper gives an outline of the new method and the results of basic investigation.

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A number of obstacle detection systems are now in operation at level crossings to prevent collisions between trains and large vehicles. However, these are not suitable for detecting people on two-wheeled vehicles or pedestrians, who are also frequently involved in accidents at level crossings. To address this problem, we have been developing a new obstacle detection system that utilizes stereo cameras and image processing technology. The stereo camera system is more effective than a single camera system because it measures the three-dimensional shape of obstacles on crossings. This paper describes the development of the new obstacle detection system and its field test results.

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Building up effective and economical countermeasures is needed to prevent lightning damage to railway signalling systems. Therefore, we measured the wayside ground potential distribution when a rail potential rise was caused by injecting a lightning surge current into a rail. Moreover, we injected a lightning surge current into the rail or wayside ground, raising their potential in order to measure the lightning overvoltages on a level crossing so that basic insulation design data could be obtained. This paper demonstrates that an effective countermeasure is to earth lightning protective devices, which are attached to the electronic train detectors on a level crossing to suppress any lightning overvoltages.

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We measured factors relating to track dynamic behaviour, such as dynamic wheel loads and rail seat forces near a rail joint induced by running vehicles. We also proposed a track dynamic model to consider the excitation by wheels passing over discontinuous fish plate rail joints. We then compared the measured and analytical results, and found a close agreement between them. We also proposed a prediction model of ballast settlement near rail joints and calculated the effects of countermeasures against joint dips on ballast settlement.

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A current design standard provides the deflection limits of structures from the viewpoint of running safety and riding comfort up to 260km/h operation. In this study, the influence of dominant parameters on the dynamic response of vehicles running on structures was examined by numerical analysis to expand the applicability of the design standard in the high-speed range. In addition, the dynamic responses of vehicles on 17 actual structures of various types with different span lengths were measured mainly through vehicle running tests. Carbody acceleration was also measured in relation to structure deflection and studied from the viewpoint of the span length and rigidity of the structures. Peak-to-peak amplitudes of carbody acceleration were approximately 1.5m/s² or less on all structures. A new provision for the railway design standard was proposed based on this study.

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This study is the first reported application of several reliability analyses to investigate the structural reliability of typical reinforced soil structures with variable heights in sliding and overturning modes, using classical or advanced reliability approaches. In this study, the sensitivities of backfill soil properties (unit weight and friction angle) and tensile strength of reinforcement to the reliability index were investigated by changing the averages and coefficients of variation. An allowable reliability index in accordance with the conventional safety factor was proposed with the corresponding tensile strength of reinforcement. The recommended load and resistance factors were calibrated based on the above allowable reliability index by the advanced first-order and second-moment (AFOSM) method with Monte Carlo stratified sampling simulation results. The recommended load and resistance design factors based on the reliability analysis showed a reasonably constant value independent of soil property and wall height but dependent on failure mode.

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Ground surface loading and unloading model tests were carried out to establish a method of evaluating the deformation behavior of a tunnel due to embanking and ground surface excavation above it. The test parameters were: ground condition (soft mortal-type M and sand-type S), loading or unloading width B and tunnel overburden H. The following conclusions were obtained from the results: 1) Non-linear tunnel deformation behavior was more noticeable with type M in the loading test and with type S in the unloading test. 2) The deformation behavior of the tunnel was more noticeable when B/H were larger. 3) It was possible to simulate the test results by FEM analysis using a non-linear ground model and a contact model between the ground and tunnel lining.

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