The railway line planning problem (LPP) plays a crucial role in determining the quality of services provided to passengers, as well as operation costs borne by railway companies. In periodic railway ...LPPs, it is common to consider passenger transfers between train lines to realize a general passenger travel cost setting in the railway system. While detecting passenger transfers requires incorporating passenger routing into mathematical formulations, thereby significantly complicating the problem. Studies on transfer-included LPPs are generally based on the Change&Go network that is constructed based on a pre-given line pool, which however is usually non-exhaustive due to computational intractability. To efficiently include passenger transfers in large-scale railway LPPs, this paper proposes a novel extended direct-service network representation of LPP, where lines are dynamically generated within the optimization process, and part of passenger transfers between lines can be precisely captured without the need for explicit modeling of passengers’ distribution on specific lines. A two-phase solution approach based on the representation is designed. The first phase formulates LPP with part of transfers as a path-based service network design model, solved using a branch-price-and-cut algorithm. The second phase conducts a neighborhood search around the first-phase solution to seek better ones when considering all passenger transfers. Numerical results showcase the good performance of the two-phase solution approach. It delivers optimal solutions in 18 out of 24 test instances for a small case and achieves optimality gaps within 2.85% across all small instances. The large case study of China’s Shandong high-speed railway network whose line pool size reaches millions demonstrates the scalability of the approach and its advantage over the traditional Change&Go method with partial line pools and an exact model developed in the paper.
•A new network representation of periodic railway line planning problem with passenger routing without line pools.•A powerful two–phase solution approach incorporating two mathematical models and a branch-price-and-cut algorithm.•Validated on the Shandong high-speed railway network in China.
Line planning decides critical service contents of a passenger railway schedule. In real-world scenarios, passengers’ travel expectations or preferences on service qualities tend to be heterogeneous ...among different origin–destination (O-D) pairs or even in the same O-D pair, which requires railway operators to schedule train services catering to those diverse passenger demands. However, previous line planning approaches either treated passengers homogeneously or roughly divided simple passenger groups by travel purposes or service types. In this paper, we view each passenger O-D pair as an individual O-D market and propose a line planning approach where concluded train lines can deliver matched service levels of trains for each O-D market. Based on the Set Covering Problem (SCP), we establish a novel bi-objective mixed integer linear programming (MILP) model that considers the benefits of both railway operators and passengers. Multiple service qualities for each passenger O-D pair, such as travel speed, direct or transfer connection, frequency, price, etc. are seen as the objects to be “covered” by train lines, to achieve a more accurate supply–demand match. Facing the potential conflicts between diverse passenger demands and limited railway supply, we formulate a series of non-rigid constraints (NRC) to achieve a non-rigid supply–demand match i.e., each O-D pair’s demands can be either guaranteed to be satisfied or satisfied as much as possible. In this manner, railway operators can testify different marketing policies and make marketing decisions regarding which O-D markets should improve, maintain, or degrade services. A heuristic rule-based adaptive iterative searching approach (ISA) is designed to solve large-scale model structures. We take the Beijing-Shanghai high-speed railway (HSR) line as the case study background. We comparatively evaluate the operation and service performances of multiple cyclic line plan scenarios, discuss the performance difference, and state our policy implication. We also recalibrate the service levels of the real-world non-cyclic line plan. The experiment results show that our proposed approach can efficiently help design the line plans based on customized marketing policies and improve the service levels of the real-world line plan.
This paper proposes a variable domain hybrid decision-based friction optimization control strategy for train multi-wheelsets. This strategy aims to achieve the stable operation of creep speed for ...train on both flat and ramped railway lines. Firstly, a transfer factor-based creep speed prediction model is proposed. The model integrates the axle load transfer mechanism in the prediction process of creep speed by the transfer factor. Then, an adaptive hybrid decision (AHD)-based weight mechanism is proposed. The AHD incorporates a dual adaptive mechanism of the axle load transfer and slipping fault to make weight decisions. Finally, a variable domain transfer search(VDTS)-based friction coefficient allocation method is proposed. The VDTS designs a finite gradient learning to correct the search domain and establishes the transfer search equation based on domain boundaries. The proposed strategy is verified on the hardware-in-the-loop(HIL)-based platform. The detailed comparative analyses are conducted with three other relevant strategies to evaluate the optimization effectiveness of the creep speed for the wheelsets, which encompass the comparison of creep speed differentials as well as the power losses in the train. The test results show that the proposed method can maintain consistent speeds of different wheelsets within the stable domain, while reducing the slipping power loss of wheelsets.
Surface defects in different railway lines experience different wheel-rail rolling contact actions owing to various railway line characteristics and vehicle operation parameters. This study focused ...on the evolution of defective wheel-rail rolling contact fatigue (RCF) behaviour under different operation conditions. Conical defects were created using an indentation apparatus. Wheel-rail RCF tests were performed using a twin-disc testing machine. Various operational conditions were simulated considering different slip ratios and wheel linear velocities on uphill and flat lines, as well as different vehicle axle loads and train configurations. The results indicate that surface damage, crack depths, and wear debris size increased only with decreasing wheel linear velocities, whereas the crack angles increased only with decreasing slip ratio. Meanwhile, both the wear rate and oxidation degree of wear debris were simultaneously affected by the slip ratio and wheel linear velocities. Under rolling conditions on flat lines, vehicle axle loads had a negligible influence on the wheel-rail RCF behaviour.
•Operation conditions were simulated considering uphill and flat railway lines, also axle loads and train configurations.•Slip ratio cannot affect surface damage, crack depths and wear debris sizes, velocities cannot affect crack angles.•RCF behavior under constant and adjustable axle load during rolling contact tests was almost identical.•Crack angles, oxidation degrees of wear debris perform some differences on uphill railway lines.
Most of the railway lines in Slovakia were built in the second half of the 19th century, or until 1918 (the establishment of Czechoslovakia). Except for the post-World War II period, when ...approximately 71 % of the Slovak lines had to be renewed, limited funds have been spent on repair and reconstruction works on the lines located in the Slovak territory. As some trans-European corridors cross the Slovak territory and the Slovak Republic assumed obligations arising from the AGC and AGTC agreements, the line modernization is more than desirable. The primary objective of the modernisation of railway lines in the territory of Slovakia is to ensure a high-quality and safe railway, which by its qualitative parameters corresponds to the standards of developed European countries. In this context, the paper deals with a section of the modernised corridor no. Va, specifically the section Považská Teplá - Žilina. During the period 2014-2017, quality diagnostics of the performed work was carried out on the sub-ballast layers of the above-mentioned line. Consequently, we carried out an analysis of the obtained values of the deformation resistance of the subgrade surface, as the weakest element in the construction of the sub-ballast layers.
In the field of civil engineering, specifically within railway projects, the adoption of Building Information Modeling (BIM) has become imperative. However, the sector's adherence to traditional ...methods for infrastructure design and management has delayed the widespread adoption of BIM. This paper describes a BIM-centered methodology applied to a real-world High-Speed Railway Line (HSRL) project. Through an extensive examination of HSRL design parameters and the integration of various BIM-based tools, a 3D parametric design model is generated. This model serves as the foundation for evaluating up to five design alternatives, considering technical and economic aspects. Furthermore, a degradation model is proposed to assess alternative performance over the infrastructure's full lifecycle under specific rail traffic assumptions. This facilitates a rapid evaluation of alignment design's impact on maintenance costs. The paper draws two main conclusions with potential benefits for both private companies and railway administrations: Firstly, BIM proves feasible and advantageous despite some interoperability challenges, highlighting the need for continued advancements in BIM software compatibility. Secondly, the proposed approach can potentially lead to up to 40% cost savings in maintenance for railway administrations.
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•The influence of the horizontal alignment design of a High-Speed Railway Line (HSRL) on its maintenance period is analyzed.•A BIM-centered method has been proposed to evaluate both construction and tamping costs.•The importance of considering the maintenance costs during the design phase has been demonstrated.•The interoperation between an alignment design tool and a budget management software has been tested.•The method is applied to a real HSRL project in Spain.
•The integration of line planning, timetabling and robustness is new.•Coordinated line plans and timetables are built from scratch.•Two insights and proofs on timetable-infeasibility are ...proposed.•The inclusion of limited shunt capacity in line plan and timetable optimization.•The approach is validated on the DSB S-tog network in Copenhagen.
We propose a heuristic algorithm to build a railway line plan from scratch that minimizes passenger travel time and operator cost and for which a feasible and robust timetable exists. A line planning module and a timetabling module work iteratively and interactively. The line planning module creates an initial line plan. The timetabling module evaluates the line plan and identifies a critical line based on minimum buffer times between train pairs. The line planning module proposes a new line plan in which the time length of the critical line is modified in order to provide more flexibility in the schedule. This flexibility is used during timetabling to improve the robustness of the railway system. The algorithm is validated on the DSB S-tog network of Copenhagen, which is a high frequency railway system, where overtakings are not allowed. This network has a rather simple structure, but is constrained by limited shunt capacity. While the operator and passenger cost remain close to those of the initially and (for these costs) optimally built line plan, the timetable corresponding to the finally developed robust line plan significantly improves the minimum buffer time, and thus the robustness, in eight out of ten studied cases.
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.
•There is a possibility how to increase capacity of a segment of the single track line without doubling in a full length.•This research is a chance for trains running in opposite directions, but it is usable also for trains in the same direction.•The utility of extended Switch Point Area is on line capacity and timetable stability.
The quantitative concentration of alloying elements in low-alloyed copper alloys is an important factor in forming electrical and mechanical characteristics. It is known that severe plastic ...deformation is accompanied by both a substantial refinement of the structure and changes in the kinetics of phase transformations during the deformation and the post-deformation thermal treatment. This paper presents the results of a comparative analysis of the Cu–0.2Cr and Cu–1.1Cr alloys subjected to equal-channel angular pressing at room temperature. The analysis was performed for the grain structure, solid solution, and second-phase particles using transmission electron microscopy, scanning electron microscopy, X-ray crystal analysis, and the small-angle diffraction method. It was found that the level of structure refinement and mechanical characteristics after equal-channel angular pressing was almost the same for both studied alloys. Post-deformation aging of the Cu–0.2Cr alloy leads to the development of polygonization and re-crystallization within it. The aging of the Cu–1.1Cr alloy shows a better thermal stability than that of the Cu–0.2Cr alloy. In the Cu–1.1Cr alloy, after aging, in comparison with Cu–0.2Cr, a denser-packed ensemble of fine particles with an average size of 54 ± 2 nm is formed. In this case, the average size of fragments is 270 ± 15 nm and the ultimate tensile strength reaches 485 MPa.
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