Abstract: With the increase of traffic pressure at urban intersections, the prohibition of left-turn vehicles has become an important means to alleviate supersaturated traffic congestion and improve traffic efficiency. The purpose of this paper is to overcome the limitations of the existing left-turn prohibition methods, which mostly investigate only a single intersection, but lack of scientific evaluation basis for left-turn prohibition measures in arterial roads and regions. Based on the advantages of regional traffic state description of Macroscopic Fundamental Diagram (MFD), the evaluation method of the left-turn prohibition traffic organization has been established for different evaluation scopes, such as an isolated intersection, multi-intersections, and regional intersections, respectively. Firstly, the left-turn prohibition flow transfer of intersection is described based on the logit model. Secondly, the MFD after the left-turn prohibition is constructed with the transfer proportion of left-turn flow and the road grade as the key factors, and the evaluation model of the left-turn prohibition traffic organization based on MFD is established. Finally, the reliability of the model is evaluated by an example analysis of the Beijing Road area in Kunming. The results show that the use of left-turn prohibition at an isolated intersection or arterial road can improve the traffic operation efficiency of the road network when the proportion of left-turn traffic is less than 15% in the simulation area; only left-turn prohibition at the isolated intersection can improve the operation efficiency of the road network when the proportion of left-turn traffic is 15%~ 20%; and in any state of left-turn traffic ratio, prohibition left-turn on the whole region will reduce the traffic operation efficiency.

Key words: urban traffic, left-turn prohibition, macroscopic fundamental diagram, traffic simulation, traffic organization

摘要： 随着城市交叉口交通压力增加，采用禁止左转车辆通行成为缓解过饱和交通拥堵和提升通行效率的重要手段。为克服现有禁左方法多以单个交叉口为研究对象，而对干道和区域禁左措施缺乏科学评价依据的局限性，本文基于宏观基本图(Macroscopic Fundamental Diagram，MFD) 区域性交通状态刻画的优势，分别建立单点、干道及区域等不同评价范围的禁左交通组织评价方法。首先，基于Logit模型刻画交叉口禁左后流量转移；其次，以左转流量转移比例与道路等级为关键因素构建禁左后的MFD，得出基于MFD的禁左交通组织评价模型；最后，通过对昆明市北京路片区VISSIM交通仿真分析评价模型可靠性。结果表明：在仿真区域内，当左转车流占比小于 15%时，采用单点禁左或干道禁左可以提升路网交通运行效率；当左转车流占比为15%~20%时， 仅单点禁左可以提升路网运行效率；而在任何左转车流比例状态下，对区域禁左均会降低交通运行效率。

关键词: 城市交通, 禁左, 宏观基本图, 交通仿真, 交通组织