Single-track Railway Line Research Articles

Stress-strain states of reinforced concrete spans of a railroad overpass using a spatial finite element model

The paper presents the results of computational analysis of the stress-strain state of reinforced concrete spans of the railway (single-track railway line) overpass over the highway, under specified loads using spatial finite element models. The static load consists of a cohesion of three TEM-18 diesel locomotives and two loaded gondola cars (up to 25 tons per axle). The purpose of this study was to ensure reliable and safe operation of artificial structures on the railroads, as there is a constant increase in transit freight trains from China through the territory of Kazakhstan to near and far abroad, and often the load on the axle reaches 25 tons, and sometimes larger values – up to 27 tons per axle. The results of the study are recommended to be used for inspections and tests of typical girder bridge spans, as well as in the case of monitoring their technical condition with increasing operational loads.

Quantum Annealing in the NISQ Era: Railway Conflict Management

We are in the noisy intermediate-scale quantum (NISQ) devices' era, in which quantum hardware has become available for application in real-world problems. However, demonstrations of the usefulness of such NISQ devices are still rare. In this work, we consider a practical railway dispatching problem: delay and conflict management on single-track railway lines. We examine the train dispatching consequences of the arrival of an already delayed train to a given network segment. This problem is computationally hard and needs to be solved almost in real time. We introduce a quadratic unconstrained binary optimization (QUBO) model of this problem, which is compatible with the emerging quantum annealing technology. The model's instances can be executed on present-day quantum annealers. As a proof-of-concept, we solve selected real-life problems from the Polish railway network using D-Wave quantum annealers. As a reference, we also provide solutions calculated with classical methods, including the conventional solution of a linear integer version of the model as well as the solution of the QUBO model using a tensor network-based algorithm. Our preliminary results illustrate the degree of difficulty of real-life railway instances for the current quantum annealing technology. Moreover, our analysis shows that the new generation of quantum annealers (the advantage system) does not perform well on those instances, either.

Improving single-track railway line capacity using extended station switch point area

The paper focuses on the possible capacity improvement of a segment between two stations of a single-track railway line by using of extended station switch point area and on methods assessing the capacity of such railway infrastructure, where a part of a single-track line segment being not equipped itself with e.g. line blocks becomes partially double-tracked. These methods can extend state-or-art general capacity assessment methods and allow more detailed assessment in this specific case. The research was conducted on three levels. The first is only analytic, the second is based on the developed own mesoscopic stochastic simulation model and the third is based on a stochastic microsimulation model elaborated by using the OpenTrack software. Divided solutions on each level can provide assessments with different demands on computation and model development. Stepwise solutions at the individual level may rationalize capacity assessment.

Impact Assessment of Interlocking Systems on Single-Track Railway Lines as a Measure Leading to Resilient Railway System

Railway systems should be resilient to play a key role in creating sustainable development. Single-track railway lines are seen as potential bottlenecks due to limited capacity. More advanced railway interlocking systems (such as ETCS or satellite-based control systems) are being developed. On the other hand, the installation of these interlocking systems is a complex and time-consuming and costly task. For this reason, it is necessary to recognize the impact of potentially installed system with capacity, stability of timetable, quality, and other associated effects. The assessment is based on a set of simulation experiments using stochastic microscopic simulation model in the OpenTrack software tool. The focus is on railway operation with automatic block and automatic line blocking systems. If these two systems will have positive capacity effects, it is a basic presumption also for systems such as moving block (e.g., ETCS L3) to be effective. Research has shown that the significance of such measures can be best supported by linking to a matching timetable concept that will make full use of the benefits offered by these interlocking systems. The results reached in this research should be potentially applied, for example, by prioritizing of single-track railway lines for possible installation of such interlocking system. It can be achieved based on the capacity and operational effects examined.

A virtual resource-based method for formulating the safety headway of opposing trains arriving at the same station on a single-track railway line

ABSTRACT In train rescheduling, the arrival and departure times of trains at stations are normally constrained by many operations rules that must be respected. Therefore, different methods were proposed to describe train operations for preventing train conflicts, especially concerning the safety headways. This paper develops a virtual resource-based method in place of the commonly used big-M method and ‘either-or’ constraints for reformulating the safety headway of opposing trains arriving at the same station on a single-track rail. This new formulation can provide an efficient decomposition mechanism by decomposing the original complex problem into several single train-based subproblems. A resource-oriented mixed-integer linear programming model based on a time-space network is developed to minimize the total train delay time with cumulative flow variables used to describe time-space resources occupation. We also present a set of numerical experiments based on a single-track railway line in China to evaluate the validity of the proposed method.

Railway bridge survey

This scientific article addresses the issues of a survey of bridges in order to determine the need for reconstruction or repair measures at these facilities and to collect baseline data for the dismantling of railway reconstruction projects. Inspection of culverts is carried out in order to determine the need for the appointment of reconstructive or repair measures at these facilities and to collect baseline data for the development of railway reconstruction projects. An approximate list of survey work and measurements is given. The calculation models for the analysis of the stress-strain state (VAT) and the modal analysis of the structure are constructed according to the data provided in the form of working documentation for the structure in question. Models of reinforced concrete elements of the supporting structures of the overpass allow for the joint work of reinforcing elements and concrete filling. Concrete filling of structures of reinforced concrete blocks of superstructures of 16.5 m and 23.6 m, as well as frames and pedestals of intermediate supports of the overpass, are specified by volume elements. Reinforcing structural elements (frames, grids, wire bundles for prestressing concrete) of spans and structures of intermediate supports are defined by bar elements and take into account their spatial location in the concrete filling. The results of the calculation analysis of the supporting structures of the overpass through the single-track railway line are presented.

Development of a methodology for determining an energy efficient technology for the freight transportation on a singletrack railway line

In the context of the search for strategies for the development of railway infrastructure, it is important to theoretically substantiate the choice of constructive and organizational measures that will allow the development of promising passenger and freight traffic. This study proposes an approach to determining the rational parameters of energy efficient technology for the transportation of freights on the site in the context of the implementation of one of the reconstruction measures - modern dispatch centralization of train traffic control. The main aim of research is to develop a methodology for determining an energy efficient technology for transporting freights on a single-track railway line. It is proposed to use analytical methods for calculating the average speed of trains with a combination of micromodeling of traction characteristics of freight trains of different mass. Theoretical calculations of the change in the section speed were carried out when the dispatch centralization was introduced, taking into account the choice of various options for the mass of freight trains. The calculations performed for a single-track line and the dependences of the cost change per one shipped carriage and the section speed on the train mass were obtained, which made it possible to determine the optimal parameters of the energy-efficient technology for the transportation of freights by the line. The proposed method for determining the energy efficient technology for the transportation of freights can be used in the technical and economic calculations of projects for the implementation of various systems of train dispatch control on single-track railway lines.

An Innovative Approach to Surveying the Geometry of Visibility Triangles at Railway Level Crossings.

Railway level crossings (RLCs) in Poland are classified according to their protection systems. Category D, which is a form of passive RLC, aims to ensure safe and efficient operation. Surveying is essential to prepare and control the geometry of the visibility triangles used at RLCs. This article presents a new approach to monitoring the geometry of visibility triangles of RLCs using an electronic total station and a magnetic measuring square (MMS). Its main assumptions are presented together with the application of the innovative measuring instruments. Visibility is demonstrated taking into account the angles of intersection of the road axis with the track axis of the railway line and additional attributes related to the analysis and evaluation of general visibility conditions. The research highlights controversies that have received special attention against the background of the safety status of railway level crossings. As a case study, the RLC located on a single-track railway line in Poland is examined. The final section presents applications of the results obtained according to the proposed methodology. It is shown that the proposed approach is practical and effective. In addition to surveyors, the survey methodology can be used by road and rail traffic engineers and policy makers to further improve traffic safety at RLCs. This is an important global research task.

Coordinating maintenance windows and train traffic: a case study

This paper concerns a case study for optimal planning and coordination of railway maintenance windows and train traffic. The purpose is to validate a previously presented optimization model on a demanding real-life problem instance and to obtain results that apply in similar planning situations. A mixed integer linear programming model is used for a 913 km long, single-track railway line through the northern part of Sweden, with traffic consisting of 82 trains per day, most of which are freight trains. Cyclic 1-day schedules are produced, which show that 2 h long maintenance windows can be scheduled with small adjustments of the train traffic. The sensitivity for cost changes is studied, which shows that the train costs must increase by more than 30% in order to change the structure of the window solutions. Resource efficient window schedules are obtained by assigning maintenance teams to all windows while respecting crew work and rest time restrictions. A comparison with manually constructed plans from the Swedish Transport Administration indicates that larger window volumes can be scheduled at a lower cost and with solution structures which are deemed reasonable and useful as guidance for constructing the real window patterns. Finally, we estimate that using an integrated planning approach (where maintenance and trains are jointly planned) instead of a sequential approach (where a train timetable has precedence over the maintenance windows), will give maintenance cost savings of 11–17%, without incurring any large cost increases for the train traffic. The paper also presents a method for achieving cyclic schedules without any period-deciding variables, and discusses the consequences of the aggregated capacity usage model that has been adopted.

The Delay Simulation on Hierarchical Structure for Semi-Double Track of Railway Line Using Max-Plus Algebra

The persistently inequality of development between major cities and surrounding areas caused the displacement process, that are transport of supplies or human itself (urbanization) or commonly known as the transportation. The government has set a number of policies to overcome transportation problems, for example construct a double track railway line. This study aimed to find an alternative solution to overcome the problems of transportation, especially railway line by optimizing of using single track railway line which is given the term semi-double track using Petri Nets and Max-Plus Algebra. In the previous research, a Max-Plus algebra model has been developed based on the hierarchical structure of semi-double track railway line. In this research, the model is simulated against the problem of delay.

Relative train length and the infrastructure required to mitigate delays from operating combinations of normal and over-length freight trains on single-track railway lines in North America

Distributed power locomotives have facilitated longer heavy-haul freight trains that improve the efficiency of railway operations. In North America, where the majority of mainlines are single track, the potential operational and economic advantages of long trains are limited by the inadequate length of many existing passing sidings (passing loops). To alleviate the challenge of operating trains that exceed the length of passing sidings, railways preserve the mainline capacity by extending passing sidings. However, industry practitioners rarely optimize the extent of infrastructure investment for the volume of over-length train traffic on a particular route. This paper investigates how different combinations of normal and over-length trains, and their relative lengths, relate to the number of siding extensions necessary to mitigate the delay performance of over-length train operation on a single-track rail corridor. The experiments used Rail Traffic Controller simulation software to determine train delay for various combinations of short and long train lengths under different directional distributions of a given daily railcar throughput volume. Simulation results suggest a relationship between the ratio of train lengths and the infrastructure expansion required to eliminate the delay introduced by operating over-length trains on the initial route. Over-length trains exhibit delay benefits from siding extensions while short trains are relatively insensitive to the expanded infrastructure. Assigning directional preference to over-length trains improves the overall average long-train delay at the expense of delay to short trains. These results will allow railway practitioners to make more informed decisions on the optimal incremental capital expansion strategy for the operation of over-length trains.

Computation of practical capacity in single-track railway lines based on computing the minimum buffer times

Defining the exact amount of capacity in main line railway lines is a key strategic criterion in selection of railway development alternatives. The method of computation of capacity in single-track railway lines is different from double or more track ones. The UIC 406 leaflet defined an invaluable method to compute the capacity on the basis of compressing the actual timetables. In this paper, some new methods are proposed to define the exact amount of practical capacity based on computing the minimum required buffer times during compression process in single-track railway lines. Finally, a bottleneck in Iran mainline railway network is analysed as the case study.

An efficient train scheduling algorithm on a single-track railway system

Since scheduling trains on a single-track railway line is an NP-hard problem, this paper proposes an efficient heuristic algorithm based on a train movement simulation method to search for the near-optimal train timetables within the acceptable computational time. Specifically, the time–space statuses of trains in the railway system are firstly divided into three categories, including dwelling at a station, waiting at a station and traveling on a segment. A check algorithm is particularly proposed to guarantee the feasibility of transition among different statuses in which each status transition is defined as a discrete event. Several detailed operation rules are also developed to clarify the scheduling procedure in some special cases. We then design an iterative discrete event simulation-based train scheduling method, namely, train status transition approach (TSTA), in which the status transition check algorithm and operation rules are incorporated. Finally, we implement some extensive experiments by using randomly generated data set to show the effectiveness and efficiency of the proposed TSTA.

IMPROVEMENT OF SUBURBAN RAILWAY SERVICES BY INFRASTRUCTURE AND TIMETABLE MODIFICATIONS BASED ON SIMULATION MODELLING

As part of this research, a computer model of the existing bidirectional single-track railway line section between Zagreb Glavni and Turopolje railway stations has been developed, and it has been modified with the aim of developing a new model of the double-track line on this line section, and which in relation to the existing conditions also includes additionally the new stop Donja Lomnica. The purpose of developing the new model of the double-track line is to study the possibility of introducing a new plan of cyclic timetable of the suburban and regional trains that would significantly improve the quality of existing service in railway suburban traffic of the city of Zagreb. The procedure of single-track line model modification has been performed based on simulation of railway operations in the station areas with the aim of improvement of line capacity necessary for introduction of new solution of the cyclic timetable. Within this approach, the solutions for modification of railway infrastructure in stations have been selected which have proven to be the best regarding the achievement of the mentioned purpose. As part of this work, a new solution of cyclic timetable of suburban and regional trains on the new model of the double-track railway line has been proposed by taking into consideration the existing characteristics of traffic of other trains on the observed railway line section, as in Zagreb Glavni railway station which represents the main node in the network. Stability of this cyclic timetable has been tested by the application of three different simulation scenarios. The results of this research have proven that the introduction of the new model of double-track line can enable stable application of the proposed cyclic timetable.

Simultaneous locomotive assignment and train scheduling on a single-track railway line: A simulation-based optimization approach

• Two optimization models for integrated problem are formulated. • We propose an efficient approach to assign locomotives and schedule trains. • Numerical experiments validate the effectiveness of the solution approach. This paper aims to assign locomotives to unscheduled trains with pre-planned departure times instead of trains with a pre-scheduled timetable on a single-track railway line. Considering both rigorous and relaxed situations, this paper formulates two mixed-integer programming models of the integrated optimization models, to simultaneously assign locomotives to trains and schedule trains, so that train delay is minimized. In order to solve these problems within reasonable computational times, we develop an efficient optimization approach on the basis of designed locomotive assignment rules and train movement simulation methods. For comparison purposes, two heuristics, including local branching method and relaxation induced neighborhood search approach which can be embedded into an optimization solver to effectively solve mixed-integer programming models, are also introduced. Finally, we implement extensive numerical experiments to validate the dependability and effectiveness of the proposed optimization models and approaches.

Multi-train trajectory optimization for energy efficiency and delay recovery on single-track railway lines

This paper proposes a novel multi-train trajectory optimization for single-track lines. We restrict our attention to delay cases aiming at finding optimal speed profiles, which reduce delays and save energy consumption. A multi-train trajectory optimization method is proposed to find optimal meeting locations, arrival/departure times, and speed trajectories of multiple trains within the time and speed windows. The proposed method first finds timetable constraint sets for trains under delayed situations. The timetable constraint sets provide drivable, feasible, and energy-efficient time and speed windows along the trains’ routes. The multi-train trajectory optimization method uses minimizing energy consumption and reducing delays as the objective functions, and takes into account each train’s operational constraints as well as constraints to avoid conflicts between adjacent trains. Three driving strategies of delay-recovery, energy-efficient and on-time driving, are proposed and combined in the optimization objective selection for different delay scenarios. The multi-train trajectory optimization is formulated as a multiple-phase optimal control problem and solved by a pseudospectral method. The proposed method is applied in case studies of opposite trains running on a Dutch single-track railway corridor with different initial delay scenarios. The results show that our method is able to produce a feasible schedule with energy-efficient speed trajectories for all interacting trains.

Delays for passenger trains on a regional railway line in southern Sweden

The aim of this article is to study how selected variables influence delays in train traffic. Data has been collected on train movements, timetables, weather and capacity utilization on a highly utilized single-track railway line in southern Sweden during 2014. Based on this dataset, we have analysed how different factors affect delays in passenger traffic. We measure delays in a novel way, as deviations from the scheduled duration for each line section and station stop, not as deviations from a published or operational timetable, and this allows us to identify when and where the delays first occur. Average delays were much larger at station stops. The most significant factor affecting delays was the scheduled duration time at station stops and the existence of margins on line sections. If trains arrive to a line section or station stop slightly delayed they speed up the activity, otherwise they are typically delayed. The influence of weather was less significant and somewhat contradictory: snow and cold temperatures increase delays on line sections but reduce them at station stops, while precipitation made no difference. Capacity utilization seems to have a negative correlation with delays, but we have too little variation in the levels to be confident. All studied variables, except for precipitation, have impacts that are statistically significant to a very high degree of confidence, using both t-tests and regression analysis. The results of this study have important practical implications for timetable construction; for instance we estimate that a reallocation of scheduled time at stations could reduce delays by as much as 80%. (Less)

Delay management and energy consumption minimisation on a single‐track railway

To become more competitive, railways are developing methods and technologies that enable cost reduction, higher capacity, better punctuality and greater sustainability. The authors of this study address the last two objectives and propose a method that can be used to minimise the impact of a single delay on the system by reducing both the deviation from timetabled arrival at timing points and the energy consumed by trains. The technique uses a combined macro- and microscopic level approach in an optimisation algorithm to calculate the maximum speed a train should travel at on different sections of its route, so that the train meets time constraints and saves energy. The algorithm interacts with the traffic management system to obtain the applicable time constraints. The initial results from a case study based on a single-track railway line show that applying this method to a freight train that needs to pass a late running passenger train at a loop and to arrive on time at its last station allows a 9% reduction in energy use by comparison with a situation where the freight train trajectory is not adjusted as a function of the actual traffic conditions.

Rebuilding track layouts on a single-track railway line to accommodate increased traffic volume

Rebuilding track layouts on a single-track railway line to accommodate increased traffic volume

Capacity of Single-Track Railway Lines with Short Sidings to Support Operation of Long Freight Trains

Use of distributed-power locomotives in heavy-haul service has allowed for greater efficiencies through operation of longer freight trains. In North America, where the majority of main-line routes are single track, the potential economic and operational advantages offered by long trains are constrained by the inadequate length of many existing passing sidings. To implement longer trains, railroad operators may run long trains in a single direction or fleet trains or extend sidings enough to facilitate bidirectional operation of long trains. This research seeks to characterize the interaction between passing siding and train lengths and the subsequent effect on train delay. The operation of a single-track line is simulated under different combinations of freight throughput, percent of long sidings, percent of railcars in long trains, and directional distribution of long trains. The experiment design scenarios are simulated by using Rail Traffic Controller software. Results indicate that routes with roughly 50% of long sidings eliminate any delay-based consequences of running long trains on the route. Thus, to operate with a high percentage of long trains, only half of the sidings on a route need to be extended to maintain the baseline level of service. These results are expanded through discussion of their practical application in planning programs to either extend existing sidings or construct new longer-length sidings. The findings can streamline the decision-making process associated with capital expansion projects and further the understanding of relationships between siding and train lengths, thereby facilitating the sustainable expansion of existing rail corridors in anticipation of future demand.