Abstract
It is a common practice to improve the punctuality of a railway service by the addition of time margins during the planning process of a timetable. Due to the capacity constraints of the railway network, a limited amount of time margins can be inserted. The paper presents a model and heuristic technique to find the better position for the limited amount of time margins (headway buffers and running time supplements) in a train timetable. The aim of reallocating the time margins is to adjust an existing timetable to minimize the sum of train delays at the event of the operational disturbances. The model consists of two basic parts. Firstly, the paper treats the train timetable as a Directed Arc Graph (DAG) with the aggregation concept and proposes a heuristic technique known as Critical Time Margins Allocation (CTMA), which is based on the critical path method (CPM), to reallocate the time margins. Secondly, the paper evaluates the original and modified timetable under different disturbed situations. The case study is developed on a hypothetical small railway network and a practical timetable of single-line train timetable for the track segment of Rawalpindi to Lalamusa, Pakistan. The results show that the timetable modified with the CTMA reduces the total delay time by an average of 3.25% for the small railway network and 5.18% for the large dataset. It suggests that adding the time supplements to the proper positions in a timetable can reduce the delay propagation and increase the robustness of the timetable.
Highlights
The disturbances in railway traffic are caused by many factors within the system or from the external source
Due to the disruptions in the real-time railway operations, trains may not reach the destination on the planned time
The paper aims to contribute to the research work on the robustness as follows: (1) The paper proposes the minor but significant adjustments to the train timetables at the design stage to increase the robustness against the daily life operational disturbances
Summary
The disturbances in railway traffic are caused by many factors within the system or from the external source. (1) The paper proposes the minor but significant adjustments to the train timetables at the design stage to increase the robustness against the daily life operational disturbances. (2) The paper presents the train timetable as Directed Arc Graph (DAG) and uses the sensitivity of the critical path method (CPM) technique to reallocate the margins. Model considers both runtime supplements and headway buffers for single track train timetables and reallocates the margins to the significant activities of the train timetable.
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