How did the Transcontinental Railroad Work?

How do railroad crossing signals work?

• railroad

• Answer:

  There are sensors placed into the rails that detect the approach of a train or engine. If two or more of these are activated and stay that way, then the crossing signals are activated. If the sensors detect that the movement is stopped they are arranged so that the signals de-activate and the arms come back up. They are very complex and naturally anything that complex can and will fail. The safest crossing device ever invented is the simplest and cheapest, a safe attentive driver. Sadly, they apparently are of very limited production.