Automatic train protection
Speaking from another industry point of view. ATP has been around for more than a decade. There are dedicated train systems that have no driver, and a faultless safety record.
They did strike a problem not anticipated.
People did not want to ride a train with no driver, and ticket sales plummeted. Hence they employed a "safety operator" to sit where the driver would normally sit, and make all the pax feel good.
If a train fails it simply comes to a stop, and people were still uncomfortable. How many people will trust a pilotless plane?