“Metro Trans2021″Perseverance in Innovation: Optimization for 26-second turning-back interval

From 112 seconds to 86 seconds, what does the 26-second time difference really mean? At the beginning of August 2021, Shanghai Rail Transit Maintenance Support Co., Ltd. CRSC Branch and Thales SEC Transport (STS) completed a live demonstration together. The turning-back interval verified by the test was 86 seconds,  which is 26 seconds shorter than the current average level of Shanghai Metro Line 5 of 112 seconds, and the turn-back efficiency is greatly improved. During the MetroTrans Exhibition, Liu Huiming, Chief Technical Officer of TST, explained his understanding of several “meanings” for China Association of Metros (CAMET). For TST, the 26-second time difference means perseverance and innovation in the field of CBTC signalling system, while to carry moving block to the end is its firm belief in signalling system.


Mr. Liu told CAMET that under closed exclusive right-of-way, the signalling system plays a decisive role in the shortest operating headway. In the current train control system, it is necessary to check that the track section where the turnout is located is not occupied by a train before the turnout can be triggered. Trains on the same route can continuously track the turnout by moving block. For two trains using routes with different turnout directions, the next train can only pull and pass after the previous train clears the track section where the turnout is located. “This ‘exclusive’ turnaround area limits further improvements in turn-back capacity.” Liu said that this becomes a bottleneck that restricts capacity improvement for the current urban rail transportation industry that requires a turning-back interval of no more than 2 minutes. TST’s TSTCBTC®2.0 system introduces a turnout control method based on the actual position of the train rather than on the occupancy of the turnout section, and takes the turnout as the line resource for fine management, which changes the traditional interlocking logic that the train “monopolizes” the turnaround area through the section occupancy status. The receiving and departure process can be “continuously” tracked by moving block as in the section: the rear train can pull the turnout earlier after the front one passes the turnout, which not only greatly shortens the tracking interval, but also reduces the pulling times of key turnout. “High-performance turnaround (RET) technology enables vehicle-based application, use and release of route resources, ensuring subject consistency between applicants and users. The signals direct the trains to operate safely and orderly to make the most of the way, to be flexible in turnaround, weaving, converging, and diverging.” Liu Huiming talks about the characteristics and advantages of RET technology with great familiarity. It is TST’s adherence to the original aspiration and continuous innovation in CBTC signalling system that the 26-second reduction of turning-back interval becomes a reality.  For urban rail transportation industry, which TST is committed to serving, 26-second time difference means a more flexibility, safety and efficiency system architecture.

Now rail transit has become one of the main travel modes for urban commuters. With the rapid development and construction of cities and urban agglomerations and metropolitan areas, the passenger flow of many existing lines exceeds the long-range forecasted one, and the line full capacity has exceeded 100%. Coupled with the fact that many stations are located in the central urban area and underground, it is hard to rectify station wiring. On one side, there is the mismatch between operation capacity and passenger pressure; on the other side, there is the objective difficulty of upgrading existing lines. Thus, the fast-developing urban rail transportation industry is looking forward to a more complete and sound solution. Like many excellent peers, TST is keenly aware of the industry’s development demands and pain points. Based on its own technical capabilities, research and development concepts and business foundation, TST has proposed RET technology that is the first of its kind in China and has reached the international advanced level. “The design concept of TSTCBTC®2.0 is basically targeting the Chinese market and domestic customer needs. It is the first domestic dual redundancy CBTC system. On the basis of retaining the proven advantages of SeltracTM CBTC system (real moving blocking, bidirectional ATP/ATO, rich and flexible operation support), the system backs up CBTC system with CBTC system to maximize its high availability. Liu Huiming further explained, “This multi-vehicle efficient turnaround optimization verification project on Shanghai Metro Line 5 has passed the expert evaluation, which also fully reflects the advantages of TSTCBTC® 2.0 ‘vehicle-based and resource-centric’ moving block signalling system. It can guarantee train safety while achieving continuous and efficient operation, TSTCBTC® 2.0 represents technical development direction of new generation train control system.” Shanghai Metro Line 5 is the first metro line in China to be operated, renovated and constructed at the same time. TST TSTCBTC® 2.0 system is used for the signal renovation of the existing section and the southern extension. The system has been put into operation for nearly 3 years, and the operation interference caused by the signalling system is “0”, which provides a technical guarantee for the efficient and high-level operation of the subway. TSTCBTC® 2.0 is the first “dual CBTC” redundant system architecture, using moving block as a backup system and ensuring high availability of the system to the greatest extent. As a real moving block system, it can realize rich and flexible operation functions, providing a technical guarantee for giving full play to the advantages of unmanned driving. It can save part or even all of the axle counting, signaling machines and related cable outdoor equipment, effectively reducing construction and operation costs. “These system features all aim to ultimately address the needs of metro owners with ‘0’ operation disruption, efficient operations and reduced full life-cycle costs.” Mr. Liu said that the success of the multi-vehicle driverless RET demonstration on Shanghai Metro Line 5 means that the CBTC signalling system with “resource-centric” RET technology has become one of the important breakthroughs in the capacity upgrading of existing lines.


For the future development of TST and even the industry, 26 seconds time difference means a more rational thinking and positive action for the next generation train control system.

China Association of Metros released the “Smart City Rail Development Outline in China”, which clearly points out the direction of intelligent train development, and the specific realization path is what the industry is concerned about, “TST has also seen a lot of attempts and discussions.” Mr Liu said that he always insists on the point that the development of urban rail transit signalling system is a two-wheel drive based on customer needs and technological development. Technological development aims to achieve the final customer value. “The next generation signalling system will continuously improve operation quality by using new technology to achieve higher safety, efficiency and cost optimization.” TST takes the view that from a technical point of view, it will be the future development direction to learn from the new sensor, image recognition and other technologies and their concepts in other industrial fields to realize the autonomous and intelligent metro train control system. “The main feature of the autonomy and intelligence of a single train is that the train can perceive the surrounding environment and make correct decisions independently to complete the specified operation tasks.” Mr Liu analyzed, “For subway lines and subway network systems, perceiving the surrounding environment means the perception of the operating environment of all lines and networks, as well as the surrounding environment, including passenger flow information, transfer, etc. Intelligent operation management and intelligent OCC can be realized on this basis, which can not only perform normal operation, but also deal with operation in degraded or hazardous mode.” “We both adhere to the safety bottom line and keep up with the times by refining line resources, optimizing turnout start timing, reducing civil reconstruction risk and shortening train turning-back interval. Resource-centric train operation control technology will also be one of the key features of TST new generation signalling system.” In our opinion, signalling system innovation is making progress; TST has been on the road and never stop.