You can get way more 9s if you roll your own procedures - and each step has a way of handling failure of the other steps. Old trains had paper tickets, the loc

You can get way more 9s if you roll your own procedures - and each step has a way of handling failure of the other steps. Old trains had paper tickets, the locomotive was its own power source, the conductor had a flashlight, and the conductor could sell tickets for cash. And if everything else failed, the conductor would just let you ride for free. Now everything's so interconnected that any one part failing brings everything to a halt.