CAPACITY OF BICYCLE PLATOON FLOW AT TWO-PHASE SIGNALIZED INTERSECTION: A CASE ANALYSIS OF XI'AN CITY

摘要

Although much is known about the operation of signalized intersections, little or no empirical research has been conducted regarding bicycle capacity at these locations and the correspondent contributory factors. The purpose of this study is to accurately quantify the capacity ofbikeway at signalized intersection through a fluid dispersion approach, and ultimately the lane group capacity. Using this total dispersion of bicycle flow, a relationship is also described between bicycle volume per hour and per unit width, signal parameters (length of signal cycle and green time), bicycle flow (arrival rate, density, moving velocity) and geometric intersection distance. Through the videotaping of four intersections that have significant bicycle traffic around Xiaozhai in Xi'an, China, it is ascertained that bicycle capacity varies linearly (but limited by an asymptote domain) associated with the adjustment of these parameters. The analytical results indicate that the impact saturation flow of lane groups containing right-turning vehicles and pedestrian flow at signalized intersections on bicycles is being underestimated. If this is the case, then capacity is being overestimated through the HCM 2000 capacity model and JJ37-90 approach and intersections are not being adequately designed, due to the neglect of conflict nature of mixed traffic arrivals in competing for space.%鉴于目前对信号交叉口处自行车通行能力研究不足的 实际情况,本文基于流体扩散理论提出了一种单位宽度的 自行车流通行能力分析方法,进而可推广到整个信号交叉 口进口道的计算,同时可量北分析信号参数(信号周期、 绿灯时间)、交通流参数(到达率、密度、穿越速度)及 交叉口尺寸等指标变化对通行能力的影响.依据西安市小 寨商业区周边四个典型信号交叉口的自行车流视频采集数 据,分析结果表明上述指标变化对通行能力值的影响呈线 性关系,而通过本文所提出方法所计算得到的通行能力值 较HCM 2000标准更为接近于观测值.据此可推断以往研 究中对右转车流和行人交通对自行车通行能力影响的估计 偏低,但若采用JJ37-90计算自行车道的通行能力则结果 显然偏大,究其原因在于其忽略了对中国城市中混合交通 这一基本前提的考虑.