基于交通流生存函数的交叉口通行能力计算模型

针对基本通行能力不能全面反映道路交通状况的缺点, 提出了城市道路随机化通行能力概念; 依据评价体系定义交通中断与持续中断, 量化了城市道路交通拥堵程度; 研究了现有通行能力估计方法, 利用乘积限与寿命分布列构造并估计了交通流分布函数; 结合交叉口各入口交通流数据特性改进传统连续交通流参数模型, 提出了基于交通流生存函数的交叉口通行能力计算模型; 将该模型估计结果与道路通行能力手册HCM2010中的模型估计结果和交叉口实测流量进行误差对比。分析结果表明: 生存函数模型计算出的中断、持续中断交叉口通行能力与HCM2010中的模型计算结果误差均值分别为0.162 1与0.116 4, 方差分别为0.029 0与0.015 2, 两者误差波动均较小; 提出的计算模型结果与实测较大流量相对误差分别为9.720%、3.822%和4.936%、4.779%, 统计意义下提出的计算模型相对误差为5.871%, 估计效果稳健; 城市道路交通中断次数、可接受中断概率、交通流、速度与道路通行能力之间存在生存函数乘积限对应关系, 研究交叉口的通行能力为7 632 pcu·h^-1, 提出的计算模型估计结果更具有可靠性。可见, 提出的计算模型适用性较好, 特别在不同拥堵程度的城市道路交通区域, 通过可接受中断概率估计通行能力, 可为城市道路交通组织与管理部门提供优化目标、科学决策和易于接受的理论依据。

Calculation model of intersection capacity based on traffic flow survival function

The concept of stochastic traffic capacity of urban road was proposed for the disadvantage that the basic traffic capacity was unable to fully reflect the road traffic conditions. According to the evaluation system, the traffic breakdown and continuous breakdown were defined to quantify the degree of urban road traffic congestion. The existing estimation methods of traffic capacity were studied, and the product-limit and lifetime distribution were used to construct and estimate the traffic flow distribution function. The parameter model of traditional continuous traffic flow was improved by combining the characteristics of traffic flow data of each intersection entrance, and a calculation model of intersection capacity based on traffic flow survival function was proposed. The estimation result of the calculation model was compared with Highway Capacity Manual 2010 model and practical traffic flow of intersection to analyze the computation errors. Analysis result shows that the mean errors of intersection capacity with traffic breakdown and continuous breakdown calculated by the survival function model and HCM2010 model are 0.162 1 and 0.116 4, respectively, and the variances are 0.029 0 and 0.015 2, respectively, both have small error fluctuation. The relative errors between the results of the proposed calculation model and the measured greater traffic flow are 9.720%, 3.822% and 4.936%, 4.779%, respectively. The relative error of the proposed calculation model in a statistic sense is 5.871%, and the estimation effect is robust. There is a product-limit survival function between the traffic breakdown time, probability of acceptable breakdown, traffic flow, speed and traffic capacity. The traffic capacity of the researched intersection is 7 632 pcu·h-1, so the estimation result of the proposed calculation model is more reliable. Therefore, the proposed calculation model has high practicability, especially in urban road traffic areas with different congestion degrees. By estimating traffic capacity of the acceptable breakdown probability, the optimization objective, scientific decision and acceptable theoretical basis can be provided for urban road traffic organization and management department.