城市快速路瓶颈交通流失效生存分析

Survival Analyses of Traffic Flow Breakdown at Urban Expressway Bottlenecks

瓶颈处交通流失效(breakdown)是导致快速路拥堵的重要原因,其致因则是交通需求、驾驶行为及设施设计等多因素交互作用的结果.针对快速路常发性瓶颈失效的随机特征,基于海量检测数据,提出了快速路瓶颈失效的生存分析模型.该模型首先以速度、密度组合阈值法判断失效是否发生;然后统计失效发生时刻及发生前的交通流参数,利用生存函数描述失效发生概率与瓶颈通行能力的关系;进一步采用Cox回归模型分析瓶颈失效的影响因素.上海市内环3个典型双车道常发性瓶颈点277个交通流失效事件分析表明,在50%的失效概率下,3个瓶颈每车道通行能力分别为1341,1 552,1 662veh.h-1;通过调控主线车速及驶入匝道流量可对瓶颈失效起到有效的保护作用.利用该方法可精细化确定瓶颈点概率通行能力,并为快速路主动交通管理措施设计提供理论依据.

A major cause for the urban expressway congestion is the traffic flow breakdown at bottlenecks due to the combined effects of traffic demand, driving behavior and design of traffic facilities. For the probabilistic nature of breakdown at urban expressway recurring bottlenecks, survival-analysis models of breakdown were proposed based on a large scale of detector data. First, breakdowns were identified according to speed and density thresholds, and then traffic parameters before or during breakdown interval were collected, and the relationship between the breakdown probability and the bottleneck capacity was described by survival function. Finally, factors of bottleneck breakdowns were analyzed with Cox regression models. An analysis of 277 breakdown events at three typical two-lane recurring bottlenecks in the inner ring in Shanghai shows that the traffic capacities of a single lane at these bottlenecks are 1 341, 1 552 and 1 662 veh ·h^-1 respectively when the probability of breakdown is at 50 %. To adjust or control both the speed on the main lane and the ramp capacity can effectively prevent bottlenecks from breakdown. The probability capacity of bottlenecks can be quantified more precisely with the proposed method, which provides a theory support for an active traffic management strategies and designs.