Moving Block Signaling System Research Articles

Real-time railway traffic management under moving-block signalling: A literature review and research agenda

Railway traffic management is responsible for the detection and resolution of conflicts in case of disturbed operations. To minimise delay propagation, rescheduling decisions are taken by human dispatchers, possibly supported by mathematical models. Existing conflict detection and resolution (CDR) models mostly refer to conventional fixed-block multi-aspect signalling systems, in which minimum train headways are determined based on a preset number of blocks considering worst-case braking distances and number of signal aspects. In moving-block signalling systems, minimum headways are based on absolute braking distances. This paper reviews literature on CDR with the aim to identify gaps and to propose next steps in the research on CDR under moving-block signalling. A research agenda presents various modelling options, for which modelling approaches are proposed based on a comparative analysis.

Proposing a Train Speed Profile Generation Method in Railway Signalling Systems Based on Internet of Things (IoT): Performance and Stability Assurance

In the past years, the Internet of Things has created tremendous changes in various industries, including transportation systems and especially railway signalling systems. One of the issues that is very important in signalling systems is the design of trains speed profiles to control the movement of trains based on the defined headway and line conditions such as other trains positions. Information packet loss is one of the issues that should be considered in the field of Internet of Things and if this issue occurs, effective solutions should be adopted in the system for optimal performance. In this article, a method for generating speed profiles for moving block signalling systems in case of packet loss is proposed and the stability of the system is checked using the proposed method. Finally, we will implement the proposed method on a part of a railway line and examine the results.

A Methodology Framework for Modelling a Rail Moving Block System

In the railway field, rigorous development processes contribute to implement safe and efficient systems. Railway safety standards recommend the use of formal modelling and verification techniques to guarantee processes’ correctness and validate safety requirements. ERTMS/ETCS L3 (European Railway Traffic Management System / European Train Control System Level 3) is a European standard for interoperable railways based on the concept of Moving Block signaling systems which allows for substantial capacity gains and reduced costs. In this paper, we explain why the ETCS L3 struggles to be deployed despite the benefits it can bring. Then, we discuss the planned implementations of ETCS L3 at a European-wide scale. Finally, we present a methodology framework using formal models to verify moving block systems. This work is performed in the context of the PERFORMINGRAIL European project.

Macroscopic traffic flow in railway systems — A discussion of the applicability of fundamental diagrams

Macroscopic traffic flow theory is widely used to analyze the performance and congestion in transportation systems and urban traffic. Currently, the main area of application is road traffic, where fundamental diagrams depicting the relationship between performance parameters such as traffic density, traffic flow and vehicle speed are used to represent traffic regimes and system settings. Research on the applicability for rail traffic systems is only starting to emerge and has mainly focused on mass transit systems and moving block signaling systems, so far. The current paper provides a theoretical analysis of traffic flow properties on unidirectional railway lines. Macroscopic fundamental diagrams are established and used to analyze similarities and differences of traffic flow behavior in railway systems. It is shown how fundamental diagrams allow to pinpoint flow regimes and different phases in train traffic, which can be useful information for system design and operation planning. Railway systems are studied both in a deterministic setting allowing to analyze peak efficiency and in a stochastic setting with perturbations.

Robust Cooperative Control of Networked Train Platoons: A Negative-Imaginary Systems’ Perspective

By virtue of the wide implementation of communication-based train control (CBTC) systems and moving-block signaling systems, cooperative control for trains shows great potential in improving line utilization, passenger comfort, and operation flexibility. However, the operation of train platoons faces great challenges induced by model uncertainties, unpredictable resistances, and time-varying disturbances. To address these problems, consensus-based robust cooperative control schemes are presented in this article for both homogeneous and heterogeneous train platoons. Taking the physical connection between carriages into consideration, each train in the platoon is modeled as a negative-imaginary (NI) system, and the NI property is rigorously proved in this article. In the foundation of cooperative control theories of NI systems, robust strictly NI controllers considering the network topology are utilized to track a predefined motion reference. The proposed controllers are robust to both mass uncertainties and external disturbances. Moreover, the line utilization for the railway system and the ride comfort for the passengers are improved using the proposed control schemes. Numerical simulations are given to showcase the effectiveness and robustness of the proposed controllers.

State movement for controlling trains operating under the virtual coupling system

Train Virtual Coupling System (VCS) has been proposed as a new signalling system for controlling trains by building a group of trains as convoys in order to increase line’s capacity. This is achieved because the consecutive trains under the VCS is separated only by a relative braking distance; this is much shorter than the separation distance required in the Fixed Block Signaling (FBS) and Moving Block Signaling systems (MBS). In order to achieve the high capacity obtained from the VCS, the trains in a virtually coupled convoy should keep at a distance as close to the relative braking distance as possible and run at the same speed for maintaining the safe distance between them. In this paper, we propose a distance and velocity difference approach and introduce the multiple state movements for stimulating train’s movement under the VCS. The simulated results show that the capacity can be significantly increased and maximized in which the actual separation distance between trains when they are in convoy state is slightly longer than the minimum safe distance. It could be ensured that the train has proceeded safely in that the actual separation distance is surely longer than the minimum safe distance throughout the operation time period. In addition, we show that the trains can also proceed smoothly, in that a following train catches up with its leading train and joined in the convoy with a stable movement.

Coordinated Control in the Presence of Actuator Saturation for Multiple High-Speed Trains in the Moving Block Signaling System Mode

This paper studies coordinated control of multiple high-speed trains (HSTs) in the presence of actuator saturation. For HSTs operating on a railway line under the moving block signaling system (MBS) mode, adjacent trains are connected directly through train-to-train (T2T) wireless communication such that each train exchanges information with the adjacent trains that are inside its communication range, making all trains in a railway line a multi-agent system. A state-dependent undirected graph is introduced to depict the underlying communication topology. Coordinated control laws are established that, in addition to achieving consensus among trains at the reference displacement and speed profile and avoiding collision, preserve communication connectivity. It is worth mentioning that, for each train, only the position information from its neighboring trains is needed to cause speed and displacement consensus. The effectiveness of our proposed control laws are verified by simulation study.

Cooperative Prescribed Performance Tracking Control for Multiple High-Speed Trains in Moving Block Signaling System

If high-speed trains move under a moving block signaling (MBS) system, it is a quite challengeable and significant issue to cooperate the multiple high-speed trains, such that they are separated safely and governed steadily. As an intelligent, comprehensive, and advanced modern train operation control system, the MBS system will definitely, in the near future, replace the widely used fixed block signaling system due to its modern communication, multi-source positioning, and advanced control method. Due to the involvement of several subsystems and lots of track-side equipment, such as radio block center (RBC), global system for mobile communications-railway (GSM-R), and so on, it is a nontrivial task to develop a reliable MBS system under complex operational environments, particularly without a pivotally cooperative control method for the movement of multiple high-speed trains. This paper addresses the cooperative control for multiple high-speed trains to achieve prescribed performance tracking, i.e., the speed and the position of high-speed trains are guaranteed to be confined to specific speed limitations and allowed distances ratified by automatic train protection and moving authority, respectively. The proposed control requires no prior information of the empirical parameters of the operational resistances and online adjusts by proper adaptation laws. Theoretical analysis and simulation results are given to demonstrate the effectiveness of the proposed control methods.

Nonlinear programming methods based on closed-form expressions for optimal train control

This paper proposes a novel approach to solve the complex optimal train control problems that so far cannot be perfectly tackled by the existing methods, including the optimal control of a fleet of interacting trains, and the optimal train control involving scheduling. By dividing the track into subsections with constant speed limit and constant gradient, and assuming the train’s running resistance to be a quadratic function of speed, two different methods are proposed to solve the problems of interest. The first method assumes an operation sequence of maximum traction – speedholding – coasting – maximum braking on each subsection of the track. To maintain the mathematical tractability, the maximum tractive and maximum braking functions are restricted to be decreasing and piecewise-quadratic, based on which the terminal speed, travel distance and energy consumption of each operation can be calculated in a closed-form, given the initial speed and time duration of that operation. With these closed-form expressions, the optimal train control problem is formulated and solved as a nonlinear programming problem. To allow more flexible forms of maximum tractive and maximum braking forces, the second method applies a constant force on each subsection. Performance of these two methods is compared through a case study of the classic single-train control on a single journey. The proposed methods are further utilised to formulate more complex optimal train control problems, including scheduling a subway line while taking train control into account, and simultaneously optimising the control of a leader-follower train pair under fixed- and moving-block signalling systems.

Cooperative Control Synthesis and Stability Analysis of Multiple Trains Under Moving Signaling Systems

Emerging communication-based train control techniques are a critical foundation for automatic or semiautomatic train operation for guaranteed safety, line utilization, operation efficiency, and energy saving toward intelligent rail transportation systems. Multiple-train cooperative control encounters great challenges from train control, communications, interval coordination, and uncertainties in operational environments. This paper introduces cooperative control methods and corresponding stability criterions for multiple trains under moving-block signaling systems. Two coordination scenarios are considered, and corresponding control algorithms are proposed, and their stabilities are established using Lyapunov and invariant-set theorems. The proposed controllers hold the minimal computation complexity, i.e., only one parameter needs online tuning by virtue of an ingenious parameter estimation technique. The methodologies utilize the information of “nearest neighbor trains” through onboard sensors and train–train (T2T) communications but guarantee global deployment and performance of the multiple trains queuing. The control abilities of the algorithms under predecessor following and bidirectional architecture modes are analyzed and demonstrated to be effective via simulation studies.

Optimal design of energy-efficient ATO CBTC driving for metro lines based on NSGA-II with fuzzy parameters

One of the main priorities for metro line operators is the reduction of energy consumption, due to the environmental impact and economic cost. The new moving block signalling system CBTC (Communication Based Train Control) is being installed in order to increase the transport capacity of new metro lines, and to upgrade lines equipped with the former fixed block signalling systems. In addition, this new technology could be used to improve energy efficiency in the traffic operation, due to its capability to update the ATO (Automatic Train Operation) driving commands not only at stations but also along the journey.In this paper a new optimization algorithm is proposed to design ATO CBTC speed profiles to minimize energy consumption, generating the Pareto optimal curve. The algorithm is a multi-objective NSGA-II-F based on simulation of the train motion under uncertainty. The main source of uncertainty in the consumption calculation is the mass of the train, which is dependent on the passenger load, and it is modeled as a fuzzy number. In addition, a new method is proposed to fill running time gaps with dominated points, providing a pseudo-Pareto curve.The NSGA-II-F algorithm has been applied to design ATO CBTC optimal speed profiles in a case study of Metro de Madrid, providing additional energy savings up to 7.3% compared to former fixed block signalling systems and a well time-distributed pseudo-Pareto curve for the running times required by the traffic regulation system.

Energy saving for automatic train control in moving block signaling system

With rapid development of the railway traffic, the moving block signaling system (MBS) method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway while maintaining the required safety margins. In this framework, the tracking target point of the following train is moving forward with its leading train. This paper focuses on the energy saving tracking control of two successive trains in MBS. Nonlinear programming method is used to optimize the energy-saving speed trajectory of the following train. The real-time location of the leading train could be integrated into the optimization process. Due to simplicity, it can be used for online implementation. The feasibility and effectiveness are verified through simulation. The results show that the new method is efficient on energy saving even when disturbances present.

Modeling Moving-Block Railway Systems: A Generalized Batches Petri Net Approach

Instead of conventional signaling systems (fixed-block signaling systems), moving-block signaling systems are in use to increase transport capacity by reducing headways on railway lines. A moving-b...

Optimal trajectory planning for trains under fixed and moving signaling systems using mixed integer linear programming

The optimal trajectory planning problem for multiple trains under fixed block signaling systems and moving block signaling systems is considered. Two approaches are proposed to solve this optimal control problem for multiple trains: the greedy approach and the simultaneous approach. In each solution approach, the trajectory planning problem is transformed into a mixed integer linear programming (MILP) problem. In particular, the objective function considered is the energy consumption of trains and the nonlinear train model is approximated by a piece-wise affine model. The varying line resistance, variable speed restrictions, and maximum traction force, etc. are also included in the problem definition. In addition, the constraints caused by the leading train in a fixed or moving block signaling system are first discretized and then transformed into linear constraints using piecewise affine approximations resulting in an MILP problem. Simulation results comparing the greedy MILP approach with the simultaneous MILP approach show that the simultaneous MILP approach yields a better control performance but requires a higher computation time. Moreover, the performance of the proposed greedy and the proposed simultaneous MILP approach is also compared with that of the greedy and the simultaneous pseudospectral method, where the pseudospectral method is a state-of-the-art method for solving optimal control problems. The results show that the energy consumption and the end time violations of the greedy MILP approach are slightly larger than those of the greedy pseudospectral method, but the computation time is one to two orders of magnitude smaller. The same trend holds for the simultaneous MILP approach and the simultaneous pseudospectral method.

Peak Power Demand and Energy Consumption Reduction Strategies for Trains under Moving Block Signalling System

In the moving block signalling (MBS) system where the tracking target point of the following train is moving forward with its leading train, overload of the substations occurs when a dense queue of trains starts (or restarts) in very close distance interval. This is the peak power demand problem. Several methods have been attempted in the literature to deal with this problem through changing train’s operation strategies. However, most existing approaches reduce the service quality. In this paper, two novel approaches—“Service Headway Braking” (SHB) and “Extending Stopping Distance Interval” (ESDI)—are proposed according to available and unavailable extra station dwell times, respectively. In these two methods, the restarting times of the trains are staggered and traction periods are reduced, which lead to the reduction of peak power demand and energy consumption. Energy efficient control switching points are seen as the decision parameters. Nonlinear programming method is used to model the process. Simulation results indicate that, compared with ARL, peak power demands are reduced by 40% and 20% by applying SHB and ESDI without any arrival time delay, respectively. At the same time, energy consumptions are also reduced by 77% and 50% by applying SHB and ESDI, respectively.

Synchronisation control of trains on the railway track controlled by the moving block signalling system

It has been widely expected that moving block signalling will realise greater line capacity through shortened headways between trains. However, under the condition in which all trains are individually and manually controlled, the actual effect of introducing moving block signalling is marginal. To make full use of moving block systems, the author proposes a new scheme in which a train that follows another with minimum distance defined by the signalling system will keep the condition for a certain period of time through synchronisation control. This scheme will ensure that the minimum headways between trains will always be achieved through automatic control. In this study, the calculation result of the deceleration at which a train that follows another with the theoretical minimum distance is first shown. Then, the calculation and simulation results are shown for cases in which multiple trains simultaneously start moving or simultaneously start braking. Finally, as examples of possible applications of this scheme for the realisation of advanced rail services, the following three services are discussed together with the simulation results: (i) minimisation of departure-to-arrival headway at a platform, (ii) group operation of express trains and (iii) group operation of local trains.

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

Based on the discrete time method, an effective movement control model is designed for a group of highspeed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains' movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and rescheduling trains on the rail network.

Discrete-time movement model of a group of trains on a rail line with stochastic disturbance

This paper presents a discrete-time model to describe the movements of a group of trains, in which some operational strategies, including traction operation, braking operation and impact of stochastic disturbance, are defined. To show the dynamic characteristics of train traffic flow with stochastic disturbance, some numerical experiments on a railway line are simulated. The computational results show that the discrete-time movement model can well describe the movements of trains on a rail line with the moving-block signalling system. Comparing with the results of no disturbance, it finds that the traffic capacity of the rail line will decrease with the influence of stochastic disturbance. Additionally, the delays incurred by stochastic disturbance can be propagated to the subsequent trains, and then prolong their traversing time on the rail line. It can provide auxiliary information for rescheduling trains when the stochastic disturbance occurs on the railway.

A traffic management system for real-time traffic optimisation in railways

The increase in traffic intensity and complexity of the railway system demands new methods for real-time traffic control. This paper introduces the architecture, the approach and the current implementation of an advanced Traffic Management System (TMS) able to optimise traffic fluency in large railway networks equipped with either fixed or moving block signalling systems. The TMS takes into account both the actual position and speed of each train in the area and the actual status of the infrastructure, and the dynamic characteristics of the train and the characteristics of the infrastructure such gradients, admissible speeds, signal positions and signal patterns. Potential conflicts can be predicted in advance and solved in real time, by managing the order of trains, or using alternative routes if possible, and by issuing proper speed recommendations to train drivers. In this way, the TMS prevents or limits the number of unplanned stops and the accompanying journey time loss.

MODELING THE RAILWAY TRAFFIC USING CELLULAR AUTOMATA MODEL

The NaSch model is a probabilistic cellular automaton (CA) model for the description of single-lane highway traffic. Based on this model, we propose a new cellular automata model for the railway traffic. The signaling system adopted in this work is the moving block signaling system. In our model, the distance between the following train and its leading train takes into account the velocity of the leading train. The simulation results demonstrate that our model is suitable for simulating the railway traffic. Compared our scheme to the traditional moving-space-block scheme, it is obvious that using our scheme, not only the line capacity can be increased, but also the traffic flow states are safer.