iRail Comm. & Signalling
iRail otherwise termed Communications-Based Train Control (CBTC) is a railway signalling system that makes use of the telecommunications between the train and track equipment for the traffic management and infrastructure control. By means of the CBTC systems, the exact position of a train is known more accurately than with the traditional signalling systems. This results in a more efficient and safer way to manage the railway traffic. Metros (and other railway systems) are able to improve headways while maintaining or even improving safety. The same goes for cargo rail systems where efficiency, tracking and safety are much improved.
A CBTC system is a "continuous, automatic train control system utilizing high-resolution train location determination, independent of track circuits; continuous, high-capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing Automatic Train Protection (ATP) functions, as well as optional Automatic Train Operation (ATO) and Automatic Train Supervision (ATS) functions.", as defined in the IEEE 1474 standard.
CBTC and moving block
CBTC systems are modern railway signalling systems that can mainly be used in urban railway lines (either light or heavy) and APMs, although it could also be deployed on commuter lines. In the modern CBTC systems the trains continuously calculate and communicate their status via radio to the wayside equipment distributed along the line.
This status includes, among other parameters, the exact position, speed, travel direction and braking distance. This information allows calculation of the area potentially occupied by the train on the track. It also enables the wayside equipment to define the points on the line that must never be passed by the other trains on the same track. These points are communicated to make the trains automatically and continuously adjust their speed while maintaining the safety and comfort (jerk) requirements. So, the trains continuously receive information regarding the distance to the preceding train and are then able to adjust their safety distance accordingly.
From the signalling system perspective, the first figure shows the total occupancy of the leading train by including the whole blocks which the train is located on. This is due to the fact that it is impossible for the system to know exactly where the train actually is within these blocks. Therefore, the fixed block system only allows the following train to move up to the last unoccupied block's border.
In a moving block system as shown in the second figure, the train position and its braking curve is continuously calculated by the trains, and then communicated via radio to the wayside equipment. Thus, the wayside equipment is able to establish protected areas, each one called Limit of Movement Authority (LMA), up to the nearest obstacle (in the figure the tail of the train in front).
CBTC systems based on moving block allows the reduction of the safety distance between two consecutive trains. This distance is varying according to the continuous updates of the train location and speed, maintaining the safety requirements. This results in a reduced headway between consecutive trains and an increased transport capacity.
Levels of automation
Modern CBTC systems allow different levels of automation or Grades of Automation, GoA, as defined and classified in the IEC 62290-1. In fact, CBTC is not a synonym for "driverless" or "automated trains" although it is considered as a basic technology for this purpose.
The grades of automation available range from a manual protected operation, GoA 1 (usually applied as a fall back operation mode) to the fully automated operation, GoA 4 (Unattended Train Operation, UTO). Intermediate operation modes comprise semi-automated GoA 2 (Semi-automated Operation Mode, STO) or driverless GoA 3 (Driverless Train Operation, DTO). The latter operates without a driver in the cabin, but requires an attendant to face degraded modes of operation as well as guide the passengers in the case of emergencies. The higher the GoA, the higher the safety, functionality and performance levels must be.
CBTC systems allow optimal use of the railway infrastructure as well as achieving maximum capacity and minimum headway between operating trains, while maintaining the safety requirements. These systems are suitable for the new highly demanding urban lines, but also to be overlaid on existing lines in order to improve their performance.
Of course, in the case of upgrading existing lines the design, installation, test and commissioning stages are much more critical. This is mainly due to the challenge of deploying the overlying system without disrupting the revenue service.
The evolution of the technology and the experience gained in operation over the last 30 years means that modern CBTC systems are more reliable and less prone to failure than older train control systems. CBTC systems normally have less wayside equipment and their diagnostic and monitoring tools have been improved, which makes them easier to implement and, more importantly, easier to maintain.
CBTC technology is evolving, making use of the latest techniques and components to offer more compact systems and simpler architectures. For instance, with the advent of modern electronics it has been possible to build in redundancy so that single failures do not adversely impact operational availability.
Moreover, these systems offer complete flexibility in terms of operational schedules or timetables, enabling urban rail operators to respond to the specific traffic demand more swiftly and efficiently and to solve traffic congestion problems.
In fact, automatic operation systems have the potential to significantly reduce the headway and improve the traffic capacity compared to manual driving systems.
Finally, it is important to mention that the CBTC systems have proven to be more energy efficient than traditional manually driven systems. The use of new functionalities, such as automatic driving strategies or a better adaptation of the transport offer to the actual demand, allows significant energy savings reducing the power consumption.
The primary risk of a CBTC system is that if the communications link between any of the trains is disrupted then all or part of the system might have to enter a failsafe state until the problem is remedied. Depending on the severity of the communication loss, this state can range from vehicles temporarily reducing speed, coming to a halt or operating in a degraded mode until communications are re-established. If communication outage is permanent some sort of contingency operation must be implemented which may consist of manual operation using absolute block or, in the worst case, the substitution of an alternative form of transportation.
As a result, high availability of CBTC systems is crucial for proper operation, especially if we consider that such systems are used to increase transport capacity and reduce headway. System redundancy and recovery mechanisms must then be thoroughly checked to achieve a high robustness in operation. With the increased availability of the CBTC system, it must also be considered the need for an extensive training and periodical refresh of system operators on the recovery procedures. In fact, one of the major system hazards in CBTC systems is the probability of human error and improper application of recovery procedures if the system becomes unavailable.
Communications failures can result from equipment malfunction, electromagnetic interference, weak signal strength or saturation of the communications medium. In this case, an interruption can result in a service break or emergency brake application as real time situational awareness is a critical safety requirement for CBTC and if these interruptions are frequent enough it could seriously impact service. This is the reason why, historically, CBTC systems first implemented radio communication systems in 2003, when the required technology was mature enough for critical applications.
New Solutions for a Modern Age
Rail transit is a major infrastructure, and plays an important role in modern transport systems. Safety, reliability and convenience are the basic and first requirements on modern rail transit because pleasant travelling experience is highly required.
During the process of rail transit modernization, operators have to face challenges like provisioning of new services to increase revenues as well as convenience to passengers, easy maintenance to reduce OPEX, and lack of safe, reliable and cost-effective solutions.
A modern rail transit system consists of operation control components that cover the needs for communications, signals, electric power and many other fields. Among these, communications and signals are the portions that the ZTE iRail solution focuses on, and are the basis for the production of transport equipment to ensure traffic safety, improve transport efficiency and management.
The ZTE iRail railway communication and signalling solution is a comprehensive solution that serves as the basis for transportation to ensure train security, enhance transportation efficiency, and improve management levels for railway construction and operation companies. The ZTE iRail solution consists of the railway communication system and the railway signalling system. It provides applications and functions such as the dispatching centre, passenger freight service, video analysis, environment protection, facilities surveillance, and schedule optimization.
The railway communication system consists of the transport network, telephone network, data network, and a special railway network that transmits service information of phones, telegrams, data, faxes, photos, and video clips.
The railway communication system includes a set of independent, inter-connected subsystems, such as the data transmission subsystem, telephone exchange and access subsystem, train dispatching telephone subsystem, GSMR (or radio train dispatching system) subsystem, video surveillance subsystem, data network subsystem, video conference subsystem, radio subsystem, clock subsystem, and optical fibre on-line monitoring subsystem.
The railway signalling system includes infrastructures like railway signals, railway point switches, the railway station interlocking subsystem, block sections, and the power subsystem, to ensure traffic safety, enhance transport efficiency, improve working conditions and facilitate operation management.
Cutting-edge ICT technologies, such as the Mobile Internet, the Internet of Things, and Big data, provide more convenience and enjoyment for customers.
The ZTE iRail solution uses highly reliable technologies, for example, GSM-R/LTE-R, and highly reliable system design methodologies, for example, system engineering and V-Model, bringing high reliability to rail communications network.
The ZTE iRail solution can be deployed flexibly to meet customer requirements and to lower TCO.
Rail transit is a major infrastructure, and plays an important role in modern transport systems. Safety, reliability and convenience are the basic and first requirements on modern rail transit because pleasant travelling experience is highly required. During the process of rail transit modernization, operators have to face challenges like provisioning of new services to increase revenues as well as convenience to passengers, easy maintenance to reduce OPEX, and lack of safe, reliable and cost-effective solutions.
A modern rail transit system consists of operation control components that cover all aspects of communications, signals, electric power and many other fields. Among these, the key factors are communications and signals that are the solutions focuses and are the basis for the production of transport equipment to ensure traffic safety, improve transport efficiency and management.
Automatic train operation (ATO) is an operational safety enhancement device used to help automate operations of trains. Mainly, it is used on automated guideway transits and subways which are easier to ensure safety of humans. Most systems elect to maintain a driver (train operator) to mitigate risks associated with failures or emergencies.
Many modern systems are linked with Automatic Train Control (ATC) and in many cases Automatic Train Protection (ATP) where normal signaller operations such as route setting and train regulation are carried out by the system. The ATO and ATC/ATP systems will work together to maintain a train within a defined tolerance of its timetable.
The combined system will marginally adjust operating parameters such as the ratio of power to coast when moving and station dwell time, in order to bring a train back to the timetable slot defined for it.
Total Solutions for Railway infrastructure Systems
Whether it’s AFC, CTC, ETC or any number of other transportation system applications, for the past few years, our partners are dedicated in their efforts to provide the most stable, intelligent transportation systems to cities around the world.
With specialized technical know-how and equipped with the domains to build transportation systems on the basis of discrepant needs of various applications. With decades of experiences, the product offerings toward the market of transportation have been more well-founded and completed now.
Today, these efforts have been paid off. There is an impressive portfolio of successful case stories that can be shared. The solution is proven and reliable as well as cost effective and efficient.
Automatic Fare Collection
Automatic Fare Collection System (AFC) is one of basic station equipment that consists of automatic gate machines, ticket vending machines and ticket checking machines. In this application, stable and integrated platforms are necessarily to keep passenger flow run smoothly at peak hours; at the same time, all data will be gathered and transmitted into the control centre.
Station Management is an integrated platform that consists of Integrated Supervisory Control System (ISCS), Fire alarm system (FAS), Building Automation System (BAS) and others. Station Management System, due to its complicated systems, requires stable and scalable hardware to keep it well-functioned 24/7.
The solutions industrial and server-grade systems are well-known for ruggedized features and wide expansion which play indispensable roles in this specific application.
The solutions components are designed and functioned as front-end wayside controllers. Due to compliance with EN 50121-4, the solutions offerings are best suited in terms of wayside controllers for various systems including centralized traffic control (CTC), Automatic Train Control (ATC) and others. With EN 50121-4 compliance and development of rock solid systems and platforms, applications in wayside control are precisely monitored, delivering a more secure railway operating environment. Fire Alarm System and others.