wigwag signal

例句：

1. 1. The wigwag signal is used to indicate the direction of traffic.
   交通信号灯用于指示交通方向。
2. 2. The wigwag signal was a crucial part of the early warning system.
   交通信号灯是早期预警系统的重要组成部分。
3. 3. The wigwag signal helped to improve safety on the busy road.
   交通信号灯帮助改善了繁忙道路上的交通安全。