Technology Features Research of Japanese Railway Signal SystemThis paper begins with the developing history and technical classification of railway transportation, introduces the railway control system used in Japan, analyzes its technology features respectively from the aspects of electronic, computer and communication technology, and at last proposes the technical developing direction of future train control system.1. Introduction In the early days of railways, there was no signaling system. A station attendant showed the signal of go or stop by gestures. But people would make some mistakes which caused accidents.Signaling system prevents the accidents efficiently. Early signal system in Japan was Automatic Traffic Stop (ATS) devices. This device could automatically stop the train when it received the stop signal. Even if the driver ignored the alarm of the train-borne stop device, the device on the track could stop the train automatically.ATS-P (Automatic Train Stop Protection) was developed to raise efficiency. Using the responder to send a receive data signal, ATS-P system transmits information of the distance about the next stop to the train via the track, and then the system generates a train speed-checking pattern with these information.ATC (Automatic Train Control) system is developed to resolve problems of ATS-P. In ATC system, safety operation procedure will be activated to guarantee the safe performance of the train when the train operator made mistakes.To meet the needs of the modern massive high-efficient transportation, new traffic control systems are emerging such as ATACS (Advanced Train Administration Communication System), CBTC (Communication Based Train Control), etc. With the integration of railway signal and communication technology, track structure of new pattern and additional train-borne functions.This paper proposes the features of the current railway control system in Japan with the development history of the railway signal system as background, and then shows its key technology and developments in future. 2. Railway Signal SystemsThe first railway transportation system began to operate in 1830 between Liverpool and Manchester. Signal system was introduced to improve safety and to cope with the increase of traffic volume.In 1841, the signal technology was used at the two ends of the North Midland tunnel at the first time. The track circuit for the train detecting was invented in 1872.The following will analyze typical railway signal system developed by Japan National Railways (JNR) and East Japan Railway. For these systems, the level is determined by fixed block or moving block system. Train position locating is taken by the track circuit or onboard train locating device. The information is transmitted through the track circuit or radio. (ATS-S) system (Kera, 2000 is automatic train stop device which was introduced into JNR to prevent train collision. In a block section where a train is present, a track circuit detects the train position information, and the control device turns the signal for the section to Red. This status indicates that no other train can go into this block section. All of the other trains must stop before the section. Signals of other sections, into which a train can go, are Green or Yellow. Permitted speed is determined according to the distance to the section with the red signal. There is important relationship between the signal status of a section and the train position. The block system used in ATS which is consisted of the track circuit and signal device is based on the fixed block section. ATS-P improved to correct a weakness of ATS-S. By using digital information from a transponder, ATS-P transmits information about signal aspects and the distance to the next stop signal from the trackside to the train and uses this information to generate the train speed checking pattern. Then the computer compares the actual speed and this pattern. If the actual speed exceeds the pattern speed, the braking system will start. Different from ATS-S, ATS-P won t require the driver verify. When the train speed approaches the danger pattern, it will alarm the driver. The system engages the service brake at maximum power automatically when the speed pattern approaches the danger pattern.D (Decentralized)-ATC is an intelligent on-board system. Every train calculates its appropriate permitted speed according to the stop position information from the ATC central logic system. In high traffic density braking on time can be realized by pattern control. The cost of ground devices is reduced by using general information equipment and a decentralized system. The system contains the flexibility of be able to shorten the train headway without changing ground equipment when rolling stock performance is improved. Operability is improved by indicating the train usage on routes to drivers.Along with information technology develops so rapidly, a new railway traffic cont