我国早期交叉路口的设计，为避免交通流的冲突，多采用环形岛。这类方法在交通量相对较小的情况下有一定的作用。随着交通需求量的飞速增长，环形交叉口通行能力的缺点逐渐显露出来。按照交通工程学的理论，当一个路口的通行能力达到６０００辆／小时以上，往往采用拓宽路口、 China’s early intersection design, in order to avoid traffic flow conflicts, the use of annular island. Such methods have a certain effect in the case of relatively small traffic volume. With the rapid growth of traffic demand, the shortcomings of the traffic capacity at the roundabout gradually revealed. According to the theory of traffic engineering, when the traffic capacity of an intersection reaches more than 6000 vehicles / hour, it is often used to broaden the intersection,