It's surprising that ATC works in such a human-driven manual way. Compare to train signalling, where tracks are divided into signalled sections, and a train can

It's surprising that ATC works in such a human-driven manual way. Compare to train signalling, where tracks are divided into signalled sections, and a train cannot enter the next section until the section ahead is clear, with automated braking if a red signal is run. This system was developed over many tragic accidents. Even the Victorians came up with ways to minimise human error (see https://en.wikipedia.org/wiki/Token_(railway_signalling) https://en.wikipedia.org/wiki/Token_(railway_signalling) )