3 ms·

the UK's railways have a cheap and simple solution: two transmitters at different frequencies inside the track, the distance between them controls the maximum s

• jameshart 11y ago
  That's a very elegant solution; has the disadvantage that its failure mode is not safe - if the train fails to detect a signal at all, then it will just continue at whatever speed it likes. And of course, like a lot of physical engineering solutions, it's not built to be secure against malicious actors. Someone who broadcast fake signals could slow a train down - or confuse it into ignoring the real signals. This is the kind of thing which autonomous-driving skeptics need to keep in mind when they worry about 'how will you stop people from continually stepping out in front of self driving cars to stop them', or 'how will you stop people from jamming your lidar sensors?' How do trains stop people from interfering with these safety systems? They don't - the fact that interfering with the safe operation of a train is dangerous and subject to huge legal consequences is what stops people from doing it. Same applies to your worries about car technology. What stops people interfering with lidar? The fact that most people are not psychopaths, and they would probably go to prison if they did.