Fact-checking of timetabling principles: a case study on the relationship between planned headways and delays

The tradeoff between reliability and level of service is a central focus for railway operators and infrastructure managers. A well-performing timetable must include an optimal level of buffer time between conflicting train movements, such that a high service delivery and a high service quality are maintained. This focus on buffer time has informed the research within the fields of timetable optimization, capacity utilization and delay propagation modeling. Despite recent and ongoing advancements in these fields, there are still disconnects between the theoretical models and their application in the design, planning and evaluation of railway timetabling. Parameters that are used in timetabling, as well as, as input to the analytical assessment models, are typically derived from practical experience and based on the macroscopic limitations of a system, rather than the microscopic conflicts inherent in its signaling system. The objective of this paper is to support the design of fact-based timetables by introducing a method of applying statistical analysis of the relationship between planned headways and recorded delays to estimate the minimum feasible headway between conflicting train movements in a railway system. This method is applied on the busiest railway line in Denmark and the results from recorded operations are validated through microsimulation.

可靠性与服务水平之间的权衡是铁路运营商和基础设施管理者关注的核心问题。一份性能优良的时刻表需在列车运行冲突之间设置最优缓冲时间（buffer time），以维持高水平的服务交付与服务质量。这种对缓冲时间的关注为时刻表优化、容量利用率及延误传播建模（delay propagation modeling）等领域的研究提供了指导。尽管这些领域近年来取得了持续进展，但理论模型与其在铁路时刻表设计、规划及评估中的应用之间仍存在脱节。时刻表设计中使用的参数，以及作为分析评估模型（analytical assessment models）输入的参数，通常源于实践经验并基于系统的宏观限制，而非其信号系统（signaling system）中固有的微观冲突。本文旨在通过引入一种方法来支持基于事实的时刻表设计——该方法应用统计分析探究计划行车间隔（planned headways）与记录延误（recorded delays）之间的关系，以估算铁路系统中冲突列车运行之间的最小可行行车间隔（minimum feasible headway）。此方法已应用于丹麦最繁忙的铁路线，且记录运行的结果通过微观仿真（microsimulation）得到了验证。