The impact of rail terminal design on transit service reliability

Ensuring reliable rail transit services is an important task for transit agencies. This paper describes research of the effects of various terminal configurations on reliability of services. Besides terminals, the results could also be used for short turning infrastructure. Short turning is a very widespread measure to restore service after major disturbances and in many rail networks, additional switches are constructed to enable short turning.
In this paper, it is suggested to consider reliability already during infrastructure design and the mechanisms and effects of infrastructure design are shown. Calculations of the average delay per vehicle, regarding three main types of terminals, show the effect of frequency on the one hand and occupancy time (determined by the distance from the switches to the platform (i.e. length of the terminal), technical turning time and scheduled layover time) on the other. The substantial effect of arrival variability and the number of lines using the terminal is illustrated as well. It is shown that using stochastic variables, delays will occur, although they are not to be expected in the static case. The best performance regarding reliability is achieved, when double crossovers are situated after the platforms. Single tailtracks facilitating the turning process are only acceptable if frequencies are low. Although, , they are often used in practice as short tuning facility for high frequent services. This research shows the large impact of occupancy time on expected delays. It is recommended to minimize this time by designing short distances between switches and platform and tailtracks. Capacity management is not common use in transit. However, increasing frequencies and large deviations force to consider limited capacity, while planning infrastructure. If not, delays will occur and additional measures are necessary to solve them. This could be more expensive in the long run.

Read the full paper: Paper TRR Van Oort 2010

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