A Train Protection System So Simple, No One Can Improve On It

When you have a railroad snaking around mountains in areas where few people live, there's always the possibility of rockslides or even single boulders that can wreck a track and derail a train. In 1882, John Anderson came up with a system for the West Highland Line that travels through the Pass of Brander in Scotland, to warn approaching trains of falling rocks. It was so simple that it will remind you of when you were a child and set a rabbit trap you saw in a cartoon. The system is called Anderson's Piano, and it's worked fairly well for 140 years. It's not a perfect system- the parts get rusty and are hard to replace, but it doesn't depend on a power supply. As Tom Scott explains, so far, no one's come up with anything better.