中文摘要：

为定量研究间接左转对无信号平面交叉口交通安全的影响,选取了壶柄型交叉口和领结型交叉口两种间接左转接入形式,从交通冲突和速度方差的角度与直接左转的交叉口进行了对比分析。分析发现：领结型和壶柄型间接左转的交叉口交通冲突指数均有大幅下降,分别为直接左转交叉口冲突指数的45%和68%;在相同的主路流量、左转比例情况下,领结型和壶柄型间接左转的交叉口交织区的速度方差分别为直接左转交叉口的44%和84%。可见间接左转接入方式对无信号交叉口的交通安全有明显的改善,在次要道路条件满足的情况下,领结型交叉口对交通安全的改善作用更显著。研究结果可为合理选择间接左转接入方式提供理论依据和技术支撑。

英文摘要：

In order to quantitatively study the effects of indirect left--turning（ILT）on traffic safety at non-- signalized intersection,two types of ILT including Jug- handle intersection （JI）and Bowtie intersection （B I）are selected {or analysis. The two types are compared with direct left turning （DLT） from the perspectives of traffic conflict index and speed wriance. The analysis shows that traffic conflict indexes of JI and BI both decline significantly which are 45 % and 68% of DLT respectively. Under the same traffic volume and proportion of leftturning,the speed variances of weaving areas of JI and BI also. decline obviously which are 44% and 84% of DLT respectively. Those reductions indicate that traffic safety of indirect left turning at non--signalized intersection has improved significantly when compared to DLT and the effect of Bowtie intersection is more significant if the road conditions are suitable. The research provides a theoretical and technical support to choose reasonable ILT types for planners and designers in China.