This paper is concerned with the train timetabling problem that minimizes the total train travel time subject to a set of operational and safety requirements on a single-track rail line. A generalized resource constrained project scheduling formulation is proposed to consider segment and station capacities as limited resources, and a branch-and-bound solution procedure is presented to obtain feasible schedules with guaranteed optimality. The proposed search algorithm eliminates train conflicts chronologically by adding precedence relation constraints between conflicting trains, while the resulting subproblems are solved by the longest path algorithm that determines earliest start times for each train at segments. In order to effectively reduce the search space, a Lagrangian relaxation based lower bound rule is used to dualize segment and station capacity constraints and decompose the original complex problem into single train scheduling problems. Another exact lower bound rule is also embedded into the branch-and-bound search procedure to estimate the least train delay for resolving each existing crossing conflict in a partial schedule. In addition, this paper applies a beam search heuristic method to provide tight initial upper bounds. Based on a real-world train timetable, comprehensive numerical experiments are conducted to illustrate the computational performance of lower bound rules and evaluate several constructive heuristic methods.

Single-Track Train Timetabling with Guaranteed Optimality: Branch-and-Bound Algorithms with Enhanced Lower Bounds

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Дослідження інтенсивності руху спеціалізованих поїздопотоків в умовах ризиків

Purpose. Scientific research is aimed at gaining new knowledge about the structure of a typical regulatory and technological document (regulation) of access for private-owned train locomotives to public railway infrastructure. Methodology. To obtain relevant empirical data, the authors performed a review of previous studies on the topic of work using full-text and abstract databases. In accordance with the principles of system analysis and mathematical logic, structural-logical models of the order of interaction between the units of the operator (owner) of the public railway infrastructure and representatives of the owner of private locomotives have been developed. Findings. The authors proved: 1) the regulation of access of private train locomotives to public infrastructure is a certain procedure (technological process) for the interaction of the owner (operator) of private locomotives with the units of the owner of the infrastructure (dispatch or operational personnel, employees of commercial and carriage facilities); 2) the structure of the typical regulation includes the following blocks: the technological process, the procedure for processing transportation documents and charging fees, the procedure for operating private locomotives and preparing of locomotive’s foot-plate staff for the tour; the procedure and responsibility of the parties in case of emergency situations. Originality lies in improving the models for the organization of railway carriage traffic volumes and the movement of trains on public railways, which, unlike the existing ones, imply the decentralized management of the locomotive fleet. Practical value lies in the possibility of direct practical application of the proposed models for the creation of standard recommendations for drawing up rules for the access of private locomotives to the hauling operations on the public railway infrastructure and their practical testing in the corresponding pilot project on one of the railway lines in Ukraine. According to the research results: 1) the necessary structure of the access regulation of private train locomotives to the public railway infrastructure was determined; 2) a logical order for interpreting the interaction between the relevant units of the owner (operator) of the public railway infrastructure and locomotive traction operators (owners of private locomotives) has been created.

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Концепція регламенту доступу приватних поїзних локомотивів до залізничної інфраструктури загального користування

Purpose. The work is aimed to investigate the feasibility of transferring automatic control to low-density stations of the sections (according to the principle of supervisory control of trainline) to the operators at principal stations. Methodology. The article analyzes the work of heavy traffic sections of the Ukrainian Railways JSC. It was found out that the information workload of dispatchers who control the train movement at the sections of the main course, constantly exceeds the permissible level. The possibility of using the technology of supervisory control of train movement by the introduction of operational zones has been investigated. Findings. The authors found out that the capacity of receiving and departure tracks at the stations of the sections is extremely limited. The occupancy of run-around tracks by the out-of-work trains hinders any regulatory measures at the sections. Trains pass one after another without giving priority, that is, they pass through the section in the order in which they entered it. Due to the limited number of tracks at the pre-section intermediate station, freight trains are placed for run-around by the passenger ones at the distant approaches. This leads to a loss of service speed and reduces the level of utilization of the sections` working capacity. The introduction of operational zones will significantly reduce information flows and facilitate the work of the train dispatchers, create the necessary conditions for creative decision-making on the inter-sectional regulation, and will contribute to increase in the service speed of trains. Originality. The article developed a new technology to improve the management of train sections by dividing them into operational zones. In each zone, consisting of two or three run-arounds, the duty officer of the principal station, performing in this case the functions of the train dispatcher, can control the train movement. Practical value. It has been proposed to put trains from technical stations that idle due to uneven movement, especially the trains from the terminal stations (division points) of the locomotive circulation sections, to reserve routes of the pre-section intermediate stations. Laying the reserve tracks and their maintenance, taking into account the periodicity of use and reduced permissible speed, can be allowed according to less tight standards for the construction of the roadbed, ballast section, sleeper density, taking into account the use of switches and decommissioned tracks.

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H. I. Nesterenko

Papers

Improvement of supervisory control of train movement by means of introduction of operational zones