中文摘要：

以一级公路非信号控制路口为研究对象，旨在改善非信号路口车辆行驶的效率性和安全性。对不同的道路条件、交通流组成及交通控制等因素对远引掉头选位的影响进行分析，根据非信号控制路口交通流的特点确定远引掉头形式。采用TSIS微观仿真方法，以主路速度方差、交织区平均速度以及路网车辆平均延误作为评价指标，从行车安全性及行车效率两方面综合分析远引掉头方式的使用对路网交通流的影响。研究结果表明：当主路流量较少或过多时均不适合采用远引掉头的组织方式；当交通量适合的情况下，一级公路安全性的提高和延误的降低并非是同步的，只有当流量超过一定值（4车道为1250pcu／h，6车道为1800pcu／h）时，增加远引掉头与交叉口的距离才会达到同时提高安全与效率的改善效果。

英文摘要：

The unsignalized intersections of first class highway are taken as the research object to improve the efficiency and safety of vehicles at unsignalized intersections. The influence of different factors such as road conditions, composition of traffic flow and traffic control on U-turn location is analysed, and the U-turn form is determined according to the characteristics of traffic flow in unsignalized intersections. Using TSIS as the simulation software and taking the evaluation indexes which consist of speed variance of main-road, average speed of vehicle in weaving area and average vehicle delay of the whole road network, the impact of utilizing U-turn as the alterative of direct left turn on traffic flow is comprehensively analyzed from the aspects of safety and efficiency. The result shows that （1） it is unsuitable to choose U-turn when the main road traffic is less or too much; （2） the improvement of safety and the reduction of delay of first class highway are not synchronized when using U-turn under a suitable traffic flow condition, and only when the traffic flow exceeds a certain value （ 1 250 pcu/h for 4-lane condition, 1 800 pcu/h for 6-lane condition） will improve both safety and efficiency by increasing the distance between U-turn and unsignalized intersection.