THE rapid expansion of the high-speed rail network in China since the first line opened in 2008 to reach 26,800km today, has not been at the expense of safety. The train operation control system, as one of the key technologies underpinning the safe operation of trains on the high-speed network, has been developed through independent innovation in China.
The Chinese Train Control System (CTCS), levels 2 and 3, has been optimised and developed in recent years and is the backbone of China’s high-speed rail network. The future development of China’s railway signal system will focus on intelligence, integration, standardisation, and openness in the next few years. The objective is to lower costs by using technologies which will reduce the complexity of the system while increasing the level of protection. This will help to increase capacity and passenger satisfaction, while continuing to ensure the safety and reliability of the high-speed network, and ultimately achieving safe, efficient, and environmentally-friendly travel.
In 2017, China Railway Corporation (CRC) achieved a 9.6% increase in traffic to 3.38 billion journeys which was 265 million more than in 2016, and seven-times the number of journeys by air transport. By the end of 2017, China’s total high-speed network accounted for about two-thirds of the total global mileage.
CRC currently operates nearly 3000 high-speed EMUs, and 70% of passenger trains are operated by EMUs in China. The unique culture of China’s high-speed network has developed gradually, and high-speed rail has become a key component of the country’s public transport infrastructure.
All high-speed lines and EMUs are equipped with CTCS Level 2 or CTCS Level 3. Level 2 is mainly used on 200-250km/h lines, while Level 3 is mainly applied to lines with a maximum of 250km/h or above.
Operational efficiency
All CTCS levels are continuous data transmission control systems, which can effectively improve the safety and operational efficiency of the train control system. Level 2 uses track circuits to provide continuous movement authority, while Level 3 uses GSM-R to provide continuous movement authority through a Radio Block Centre (RBC) and train-trackside bi-directional information transmission.
Fallback systems are available for CTCS levels 2 and 3. Level 2 system adopts Level 0 as the fallback, while Level 3 system adopts Level 2. The transition between levels 3 and 2 and their respective fallback systems can be achieved automatically during train operation, and there is no need to stop the train.
Track circuit information has played an important role within CTCS thanks to the use of a uniform track circuit on the high-speed network. Level 2 provides movement authority via track circuits, while Level 3 makes a safe comparison between movement authorities provided by the RBC and the track circuits respectively. This has achieved the system integration of the level 2 and 3 systems, ameliorated Level 3 and improved the overall safety of Level 3. Track circuit information is transmitted by wayside cables, which has further strengthened the cyber security of the Level 3 train control system.
China’s high-speed rail network has also achieved full interoperability. This means that trains can switch between lines equipped with Level 3 and Level 2 without stopping. Onboard interoperability of different platforms has also been achieved, so that trains equipped with different ATP platforms can operate flexibly on the lines with different RBC platforms.
Since the overall architecture of CTCS was first proposed in 2003, we began research, testing, operation and introducing improvements to establish the complete CTCS standard technical architecture. Relevant specifications cover operation and equipment requirements, technical specifications, interfaces, testing and verification, operation and maintenance, quality standards and safety assessments.
The advantage of system standardisation is the unification of system design between different equipment manufacturers. This helped to support the rapid construction of the high-speed network, and achieve interoperability between different lines. It also reduced the safety risks in system construction and operation.
We accumulated rich engineering experience during the construction of the high-speed network. At the same time, with a large number of high-speed lines in operation, we have accumulated a large amount of data of train operation - last year, the total EMU running mileage was about 1 billion km. This is helpful in building a big data system and for data mining.
Using construction and operation data, we were able to build a large simulation test database. This database contains more than 30,000 test cases, and can produce 14,400 different scenario simulations. These test cases support both improvement of the existing system and its future development.
Automatic Train Operation (ATO) is the future of the high-speed network. ATO can increase capacity, reduce power consumption and the workload for train drivers. A Level 2+ATO system was put into operation on March 2016 on the Guangdong inter-city railway with a maximum operating speed of 200km/h. CTCS Level 3+ATO will be operational on the new Beijing - Zhangjiakou high-speed line in time for the Beijing Winter Olympics in 2022.
An AI-based high-speed train control system has been developed, which has several functions including intelligent dynamic dispatching, intelligent coordinated control, intelligent transfer dispatching, and intelligent failure diagnosis. The system optimises train dispatching across the entire network, improves emergency decision making and response, and improves operating efficiency and passenger satisfaction.
Intelligent maintenance
By using advanced technologies such as big data, deep learning, Prognostics and Health Management (PHM) and Augmented Reality (AR), an entire process management system for technology and equipment has been realised, which will improve the level of intelligent maintenance of equipment such as track circuits, while reducing life cycle costs and improving transport efficiency and safety.
The new-generation train control system will use CTCS as the kernel and will adopt new technology and evolving functionalities based on the overall CTCS architecture for maximum synergies and optimum interaction.
Our research into the next generation train control system has received recognition from global peers. Research topics including the full utilisation of satellite positioning systems, combined with IP-based radio communication technologies, will enable us to implement train location inspection and track-train data transmission, and thereby reduce trackside equipment, optimise system structure, further improve operating efficiency and reduce system and maintenance costs.
Research into improved simulated testing technologies for train control systems led to the development of laboratories that are able to simulate, under validated conditions, train performance over a complex track topology. This helps to establish the performance of the railway in advance of starting passenger services.
Research into simulated testing technologies aims to enhance the simulated testing capabilities of laboratories, to enable laboratory-simulated environments to provide more complete simulated scenarios and develop more intelligent simulation methods to ensure the safety and accuracy of CTCS software updates and data modifications. The goal is to minimise the work load of field testing.
Station-section integrated control can be adopted by reallocating and optimising the ground equipment function. This results in a simplified system structure and reduces manufacturing and maintenance costs.
To reduce the use of cables, target controllers are placed near trackside equipment, such as switches and signals, with a data link back to them. With full-electronic technologies, the aim is to reduce the use of relays as much as possible.
We are beginning high-speed line signal engineering safety assessment trials and adopting third-party safety assessments for specific engineering applications to continuously improve system safety.
Technical development is an eternal goal. As the train control system is one of the key technologies of a high-speed railway, we need to analyse and summarise the experience of CTCS, cooperate closely with worldwide colleagues, and make a contribution to the development of future train control systems around the world.
