捷運系統列車折返號誌時隔分析模式

An Analytical Model of Signal Headway at Turn-back Station for Mass Rapid Transit System

大眾捷運系統具有班次密集、便捷、環保等特性，在全世界節能減碳的風潮趨勢下，捷運系統將是紓緩都會區交通問題的重要運輸工具之一。然而捷運系統班次密集程度並非沒有限度，主因在於捷運列車運轉過程中為避免發生追撞或對撞，列車之間必須保持一定的安全間距，故號誌時隔影響列車密度甚鉅，國內外號誌時隔的研究甚多，但大多以路線中的一般通過車站作為分析對象，但實際上列車於端末站折返時亦有可能造成班次密度瓶頸，特別是配置司機員的系統。故本研究針對國內高運量捷運系統最常見的折返方式建立號誌時隔分析公式，同時以臺北捷運南港站做案例分析，經分析發現南港站折返號誌時隔約為113秒；此外由敏感度分析發現，影響折返時隔較敏感的因素包括停站時間、列車減速度、煞車有效因子、間隔安全係數與巡航速度。本研究所提出的號誌安全時距公式與敏感度分析結果，可作為未來分析列車折返效率與提升路線容量的參考。

A Mass Rapid Transit (MRT) is an electric railway system in an urban area with frequent, convenient, and green services. Under the trend of energy saving and carbon reduction, MRT has become an important transportation system in urban areas to relieve traffic congestion. However, the capacity of an MRT line is not unlimited. To avoid traffic collisions, two adjacent trains must be separated by appropriate signal headways. Consequently, signal headway becomes a key element that controls rail capacity. Most previous studies on signal headway assume that the busiest intermediate station is the bottleneck of an MRT line. However, sometimes the turn-back stations may become the bottleneck, especially for those systems with train drivers. Thus, this paper proposes an analytical model to estimate signal close-in time for common turn-back movements of MRT in Taiwan. Real parameters of Nan-gang station in the Taipei Rapid Transit System are selected for the case study. The result shows that the signal close-in time at Nan-gang station is about 113 seconds. In addition, the sensitivity analysis demonstrates that signal close-in time is highly sensitive to the station dwell time, train deceleration rate, train separation factor and cruising speed. The proposed model and the results of this study can be used to analyze the efficiency of turn-backs and to evaluate the needs of capacity improvements.