Improving train service reliability by applying an effective timetable robustness strategy

ABSTRACT

To avoid propagation of delays in dense railway timetables, it is important to ensure robustness. One strategy to improve robustness is to provide adequate amount of buffer times between trains. This study concerns how “scheduled minimum headways” should be determined in order to improve robustness in timetables. Scheduled minimum headways include technical minimum headway plus some buffer time. We propose a strategy to be implemented in timetables at the final stages of planning and prior to the operations. The main contributions of this study are 1) to propose a strategy where the size of the scheduled minimum headways is dependent on trains' travel times instead of a fixed-sized time slot and it is called “travel time dependent scheduled minimum headways” or TTDSMH, 2) to evaluate the effects of the new strategy on heterogeneity, speed, and the number of trains in timetables, 3) to show that a simple strategy can improve robustness without imposing major changes in timetables. The strategy is implemented in an Mixed Integer Linear Programming framework for timetabling and tested for some problem instances from Sweden. Results show that TTDSMH can improve robustness. The proposed strategy can be applied in intelligent transportation tools for railway timetabling.     

Short-line railroad managers discuss their industry

In the United States, the 1980 Staggers Rail Act created a positive regulatory environment for the creation of new short-line railroads. At present there are about 450 of these railroads that have less than 250 miles of trackage. This study asked managers/owners of these railroads two basic questions. First, what do you believe is the single most important trend that is currently taking place in your industry. The most frequently noted trend was the frustration of working with the larger Class 1 railroads. Five additional trends were also identified by the respondents. The second question asked the respondents if they thought the short-line sector of the rail industry will become more or less important in the next ten years and why. About 70% of the owner/managers believed their industry would become more important in the next decade. The most commonly expressed reason for this position is that the Class 1 railroads will increasingly specialize in mainline service only. Three other rationales were also enumerated. For the managers that thought their industry would become less important, the most noted reason was their trackage would not safely transport the newer very heavy bulk commodity freight cars.     

既有线不等长缓和曲线和曲线半径优化方法的探讨

本文探讨在既有线改建中无控制点或有控制点不等长缓和曲线及曲线半 径的优化方法。推荐了精度较高的不等长缓和曲线理论半径计算式。时 提供初值和优化过程中控制点的相对浮动问题提出解决办法。      

铁路施工期水力侵蚀实用预测方法

我国交通建设项目的环境评价已经开展了多年,其中施工期水力侵蚀加速系数法已在现有水土保持方案的编制工作中使用.本文对铁路工程环评中的加速侵蚀系数法进行阐述,采用USLE模型参数进一步分析、重点探讨铁路建设施工期各参数的取值和计算.根据工程特点,得出平原和丘陵地形、不同路基填料和不同土壤条件下铁路施工期水力侵蚀加速因子参考表.