这个标识代表什么意思?What does this symbol represent?

这个标识代表什么意思?What does this symbol represent?
前方环岛Ahead roundabout
前方龙卷风多发地带Ahead tornado-prone area
前方道路有两个方向Ahead road with two directions
前方道路车流汇集Ahead road with heavy traffic flow.

死记硬背题