【正文】 ) devices. This device could automatically stop the train when it received the stop signal. Even if the driver ignored the alarm of the trainborne stop device, the device on the track could stop the train automatically. ATSP (Automatic Train Stop Protection) was developed to raise efficiency. Using the responder to send a receive data signal, ATSP system transmits information of the distance about the next stop to the train via the track, and then the system generates a train speedchecking pattern with these information. ATC (Automatic Train Control) system is developed to resolve problems of ATSP. 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 highefficient 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 munication technology, track structure of new pattern and additional trainborne 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. Railway Signal Systems The 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. (ATSS) system (Kera, 2021 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. ATSP improved to correct a weakness of ATSS. By using digital information from a transponder, ATSP 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 puter pares the actual speed and this pattern. If the actual speed exceeds the pattern speed, the braking system will start. Different from ATSS, ATSP 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 onboard 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 control system appears. The system can make trains know its own position information and the distance with others. The developing system is called ATACS (advanced train administer and munication system).ATACS is a new rail control system based on information technology and ADS technology. Technology Features of Japanese Railway Signal System Decentralized Technology Feature At first ATC was used for supporting the safety superspeed system of the Japanese Shinkansen, and then was introduced to traditional rail system to shorten the distance between trains. But it can’t work effectively because of the ATC technology limit. In this background DATC (data decentralized ATC) based on ADS (autonomous and decentralized system) developed as the level 2 system. In DATC system every train is allowed to calculate its own speed. JR East developed a kind of Shinkansen DATC, in which data munication was used. The DATC is officially called DSATC. The system is used on KeihinTohoku line called DATC, while in Shinkansen called DSATC. In the ATC system the speed signal is in the drivers cab, which received permitted speed information from the ground equipment continuously. ATC s central logic system transmits ATC signals to track circuit. ATC signals are about speed information, while they are used as train detection signals. The logic device can determine the section on which a train is present by monitoring the level of received ATC signal power because the wheels of the train short the track circuits. To set the rack circuit boundary and speed pattern