Elaborated in several forms before being formally defined, virtually coupled train sets (VCTS) have become an issue for capacity increase with obvious shorter train intervals. As the station ...organization strategy is still ambiguous due to the lack of literature, the receiving routing problem for VCTS is studied in particular. First, the existing concept of VCTS is explained, which refers to the virtual connection of trains through safe and reliable communication technology, allowing short-interval collaborative operations without the need for physical equipment. Subsequently, the operating characteristics and receiving requirements are analyzed. With a summary of factors affecting receiving operations, a mathematical model is proposed with the objectives of minimizing operation duration and maximizing effectiveness, which is solved by an improved genetic algorithm (GA) with an elitist and adaptive strategy. Numerical tests are carried out 250 times based on a practical station and EMU parameters. The macro results show the valid pursuit of designed objectives with an average duration of 204.95 s and an efficiency of 91.76%. Microevolution of an optimal scheme indicates that safety requirements are met while the process duration is only 35.83% of the original CTCS-3 mode.
Busy, complex railway stations that serve as origin and termination points for a significant proportion of trains are essential to regional railway networks. Resolving conflicts between ...arrival–departure operations and shunting operations of cross-line trains and originating or terminating passenger trains in the throat area is important for safety in these multidirectional stations. The main task of this paper is to study the train platforming problem, and we consider the integration of track and route allocation with shunting route allocation on the basis of the traditional TTP problem, so as to formulate a strong anti-interference track allocation plan for busy, complex railway stations. Therefore, in view of the complex characteristics of train operation in busy, complex railway stations, we extensively examine the technical operational characteristics of various trains in multidirectional stations, which are the key constraints of the model, and establish a mixed-integer linear programming model. This model aims to balance the buffer time for track occupation and optimize the routing and scheduling of trains in stations. Furthermore, an improved genetic algorithm is proposed to effectively implement the developed model. In the case study of Guangzhou Station, the occupation analysis after the optimization of the method in this paper indicates that the shunting operations significantly interfere with arrival–departure operations in throat areas. The optimization of buffer times and track utilization times resulted in notable reductions of 30.55% and 77.82%, respectively, in quadratic differences. These outcomes provide empirical evidence supporting the feasibility of the proposed model and algorithm for addressing train platforming problems, particularly in complex, multidirectional, and heavily trafficked railway stations.
Pakistan Railway (PR) is vital to the country's transportation infrastructure, facilitating passenger and freight transportation. However, the growing number of accidents associated with PR has ...raised concerns about its overall safety. In addition, there have been limited research efforts to investigate PR accidents and their underlying causes The present study conducts a comprehensive risk assessment and safety management of PR using a semi-quantitative risk matrix approach. The study combines historical accident data and expert evaluations to assess the likelihood and consequences of different railway accident types and potential contributing factors. The descriptive statistics analysis has revealed varying degrees of severity for different types of railway accidents in Pakistan. For instance, accidents like passenger and goods train derailments and collisions at unmanned level crossings were identified as extreme and intolerable, whereas train fire accidents were categorized as high and undesirable. Moreover, accidents attributed to human error are classified as extreme and intolerable, while those caused by negligence of road users and track defects are classified as high and undesirable. The study utilized the risk matrix approach and identified critical risk areas that can help the decision-makers prioritize effective risk mitigation strategies. In light of the present study's findings, policy implications, such as investment in infrastructure to mitigate risks associated with aging or deteriorating tracks, bridges, and tunnels, and human resource development for railway personnel to improve their skills, decision-making abilities, and awareness of safety protocols, are recommended.
This paper presents the scheduling models for trainplatforming problem (TPP) by using mixed integer linear programming and job shop scheduling theory. First, the operation procedures and scheduled ...time adjustment costs of different train types specific to busy complex passenger stations are explicitly represented. Second, a multi-criteria scheduling model (MCS) for TPP without earliness and tardiness time window (ETTW) and a time window scheduling model (TWS) with ETTW for TPP are proposed. Third, various dispatching rules were designed by incorporating the dispatcher experiences with modern scheduling theory and a rule-based metaheuristic to solve the above model is presented. With solution improvement strategies analogous to those used in practice by dispatchers, the realistic size problems in acceptable time can be solved.
In order to promote the cost reduction and efficiency improvement of the logistics distribution process and to guarantee the safety of goods transportation, this paper studies the portfolio ...optimization of goods loading and the problem of simultaneous pickup and delivery vehicle routing. A balanced loading constraint was introduced to restrict loading through two aspects of axle weight bearing and lateral center-of-gravity offset. With the shortest total route length as the objective, this paper constructs a simultaneous pickup and delivery vehicle routing model with three-dimensional (3D) balanced loading constraints (3BL-VRPSPD). Additionally, a hybrid tabu search (TS) algorithm embedded loading test was proposed to solve this problem. Firstly, a heuristic insertion method was applied to determine the initial routing scheme, and the node swapping and relocation operators were designed to construct the tabu neighborhood scheme for routing optimization. On this basis, the 3D balanced loading was incorporated into the routing iteration process. A balanced loading algorithm, combining multiple-indicator ordering and maximum space division strategies (MOMD), was formulated to develop a 3D-balanced loading plan for goods with a pickup and delivery vehicle routing scheme. Finally, standard instances verified the effectiveness of the method. The results show that the proposed method can effectively optimize 3BL-VRPSPD and outperform other algorithms.
Railway out-of-gauge freight (ROF) is beyond railway gauges in its dimensions, which could be risks leading to serious railway accidents. This article presents a new methodology to search for a ...safest and more economic route of ROF by taking safety and cost objectives into consideration. In this method, a mathematical model is proposed based on the transport costs as optimization objectives with the constraints of flow balance and safety gap clearance in which ROF transport routing generation, loading outline and railway gauge double-checking algorithms are established, and then a ROF transport routing model combining transportation costs, loading outlines and railway gauges are developed. The proposed method can be used to determine the safest and more economic ROF route. A case study is used to demonstrate the application of the proposed method.
•A new ROF route generation method is established considering historical data, current ROF loading outlines and existing railway gauges.•Double-checking approach is developed to check railway gauges, safety gap clearances and operation conditions a safe ROF transportation.•A ROF route optimal model is developed by taking safety and economics into consideration to determine a ROF safe and economic transportation route.•The proposed method can be incorporated into expert systems to enhance the safe and economic operations for railway transportation.
Balancing constraints and objective functions in constrained evolutionary multiobjective optimization is not an easy task. Overemphasis on constraints satisfaction may easily lead to the search to ...get stuck in local optimal regions, and overemphasis on objectives optimization may lead to substantial search resources wasted on infeasible regions. This article proposes a constrained multiobjective optimization algorithm, called CMOEA-SDE, aiming to achieve a good balance between the above two issues. To do so, CMOEA-SDE presents a strictly constrained dominance relation and a constrained shift-based density estimation strategy. Specifically, the former defines a new dominance relation that considers both constraint satisfaction and the objective functions. It favors good feasible solutions but still leaves room for infeasible solutions to be selected. Unlike most density estimation methods, which only consider the diversity of solutions, our shift-based density estimator covers both the feasibility and the diversity of solutions. That is, our estimator shifts the solutions' positions based on the extent of the constraints they violate so that solutions violating constraints more severely are shifted to crowded areas, thus being eliminated early. Systematic experiments were conducted on four benchmark test suites and six real-world constrained multiobjective optimization problems. The experimental results suggest that the proposed algorithm can achieve very competitive performance against state-of-the-art constrained multiobjective evolutionary algorithms.
Dispatchers often set noncrossing block sections (NCBSs) for railway out-of-gauge train (OGT) running on double-track railway line for safety reasons. In this paper, we will investigate the best ...location, length, and number of noncrossing block sections to reduce railway capacity loss due to the operation of OGTs. Firstly, yielding, overtaking, stopping, starting, and other operation rules for OGTs running on double-track railway line were designed, and a simulation model based on cellular automata was further put forward. Then, an assessment model for double-track railway line capacity loss due to the operation of OGTs was set up. Some simulation experiments and the comparisons of these results were further given to achieve the optimal setting of NCBS for OGTs running on double-track railway line. In the case of NCBSs number minus one, capacity loss caused by the operation of OGTs can be reduced up to 15.2% in the upstream direction and 6.3% in the downstream direction. Also, the NCBSs should lie at the nearest block sections (BSs) to depot stations and the NCBSs lengths should be as less as possible.
For constrained multiobjective optimization problems (CMOPs), the ultimate goal is to obtain a set of well-converged and well-distributed feasible solutions to approximate the constrained Pareto ...front (CPF). Various constraints may change the position and/or shape of the CPF. This poses great challenges to the approximation of the CPF. This is especially true when the CPF mainly lies on constraint boundaries (i.e., CPF and unconstrained PF have little or even no intersection). To tackle this issue, we propose a novel dual population algorithm for approximating the CPF from both sides of the constraint boundaries. Specifically, Population1 uses the constrained-domination principle to approximate the CPF from the sides of feasible regions only; Population2 adopts an improved ϵ-constrained method to approximate the CPF from both the feasible as well as infeasible regions. Offspring generated by both populations are merged and combined with Population1 and Population2. In addition, some selected members of Population1 and Population2 are permitted to migrate to the combined populations to facilitate knowledge sharing. Systematic experiments carried out on three benchmark test suites and 10 real-world CMOPs show the proposed algorithm achieved superior or competitive performance, especially for CMOPs where the CPF is mainly located at constraint boundaries. Therefore, on the basis of dual population, approximating CPFs from both sides of feasible and infeasible regions contributes an alternative approach to solving CMOPs.
•A novel dual population algorithm for approximating the CPF from both sides of the constraint boundaries is designed.•Selected members are permitted to migrate to the combined populations to facilitate knowledge sharing.•DPACMO achieved superior performance, especially for CMOPs where the CPF is mainly located at constraint boundaries.
•A reconstruction model is developed for route planning of multimodal transportation of oversize and heavy cargo.•A method is presented to transform transportation network into multi-prism network.•K ...shortest paths algorithms are proposed for multi-route planning problem of multimodal transportation.•Improved A* algorithm is employed to enhance computational performance.•The reconstruction transportation scheme is better than the non-reconstruction one.
This paper investigates the multi-route planning problem of multimodal transportation for oversize and heavyweight cargo based on reconstruction (MM-OHC-R). Considering required reconstruction of lines or nodes, a reconstruction model for route planning of OHC is proposed. The model aims to simultaneously determine the transportation route, modes of transport as well as the lines or nodes required to be reconstructed to minimize the total cost. To attain multiple solutions, the K shortest paths algorithm is introduced and improved to solve MM-OHC-R problem. The proposed algorithm is derived from a virtual network named multi-prism network and Yen algorithm. Moreover, the algorithm is improved by introducing improved A* algorithm. A case study is conducted to validate the feasibility of the proposed model and algorithms. The results demonstrate that the usage of reconstruction measurements is able to optimize the transportation schemes and the proposed algorithm is capable of developing multiple transportation schemes to provide the support of decision making and risk prevention and control for the carrier. For the constrained MM-OHC-R problem, the improvement of the A* algorithm enhances the computation performance by reducing the size of the candidate path set effectively.
PDF
