扳道员

例句：

1. 1. The train driver was a professional signalman.
   火车司机是一名专业的信号员。
2. 2. The engineer had to be careful while operating the track.
   工程师在操作轨道时必须小心谨慎。
3. 3. The signalman gave the green light for the train to proceed.
   信号员为火车发出了前进的信号。