城市主干路交通功能可靠度量化评价方法

为了定量评价城市主干路交通功能的实现程度, 建立了城市主干路交通功能可靠度的计算方法; 分析了主干路交通功能的3个主要特征, 即承载较大交通流量, 具有较高运行速度与服务于中长距离出行, 应用可靠度理论, 提出了城市主干路交通功能可靠度的概念; 选取行程速度和直行率之积作为可靠度的计算指标, 构建了基于概率论的交通功能可靠度计算方法; 分析了2个计算指标的阈值范围, 对比了交通功能可靠度与服务水平的区别与联系; 针对郑州市2个主干路单元, 评价了其高峰和非高峰时段的交通功能可靠度。计算结果表明: 行程速度与直行率之积不相关, 且可认为二者相互独立; 主干路与支路交叉口的直行率均大于主干路与次干路交叉口的直行率, 实测的4组数据中直行率分别高出0.271、0.062、0.229和0.034;连接老城区与高新区的科学大道在高峰和非高峰时段的交通功能可靠度分别为0.803和0.702, 交通功能实现程度处于较高水平; 老城区的东风路在高峰时段的交通功能可靠度为0.386, 其交通功能特征和实现程度相对较弱, 远低于科学大道; 科学大道上3个交叉口的服务水平均为一级, 高峰和非高峰时段的路段服务水平分别处于C级、B级, 而高峰时段东风路上3个交叉口的服务水平分别为二级、二级和三级, 路段服务水平处于C级, 科学大道的整体服务水平优于东风路。可见, 交通功能可靠度评价结果与服务水平分析结果的趋势基本一致, 但与服务水平相比, 交通功能可靠度更能体现主干路的功能特征和外界因素对交通运行的随机影响。 

Quantitative evaluation method of traffic function reliability for urban arterial roads

A calculating model of traffic function reliability for urban arterial roads was established to quantitatively evaluate its achievement degree. The key features of traffic functions of arterial roads were analyzed, including the following three aspects: undertaking larger traffic volumes, having higher speed, and serving medium-long distance travel. The definition of traffic function reliability of urban arterial roads was proposed by the reliability theory. The travel speed and product of straight rates were selected as the corresponding indicators for the traffic function. The calculation method of traffic function reliability based on the probability theory was constructed. The threshold ranges of two calculation indicators were analyzed. The differencesand connections between the traffic function reliability and service level were compared. The traffic function reliability during the peak and off-peak hours was evaluated for two arterial road units in Zhengzhou. Calculation result shows that there is no correlation between the travel speed and product of straight rates, and they are further considered to be independent. The straight rates at the intersections between the arterial roads and branch roads are higher than those at the intersections between the arterial roads and sub-arterial roads. The four measured groups of straight rates are 0.271, 0.062, 0.229, and 0.034 higher, respectively. During the peak and offpeak hours, the traffic function reliability of Kexue Road, which connects the old district and high-tech development district, is 0.803 and 0.702, respectively. The achievement degree of traffic function on Kexue Road reaches a high level. The traffic function reliability of Dongfeng Road, which is located in the old district, is 0.386. The reliability characteristics and achievement degree of traffic function of Dongfeng Road are far lower than that of Kexue Road. The service levels of three intersections on Kexue Road are all level one. During the peak hours and off-peak hours, service levels of segments on Kexue Road are class B and C, respectively. The service levels during the peak hours of three intersections on Dongfeng Road are level two, level two, and level three, respectively, and the service level of segment on Dongfeng Road is class C. The service level of Kexue Road is better than that of Dongfeng Road in general. The evaluation results of traffic function reliability are basically consistent with the analysis results of service level. However, compared with the service level, the traffic function reliability for urban arterial roads can better reflect the function characteristics and effects of external factors on the urban roads traffic operation.