Remember that the Schengen 90/180 is for a midnight to midnight day. The day counter starts as soon as you enter a Schengen country, even if that is one minute to midnight it counts as a day. When you are leaving the Schengen area again if you are in a Schengen country for as little as a minute after midnight it counts as a day. Time on transportation, such as a bus, still counts as time in the Schengen area.
I never advise people to push the 90 days right to the limit for exactly the reason implicit in your question - things happen, even things over which you may have no control. What if the bus has a breakdown and you are delayed beyond midnight? Or a weather delay? You are then an illegal overstayer and subject to a huge fine.
There was a story on this website some time back of the daughter of one of our regular posters who was over by a few hours and wound up with a €500 fine. I don't completely remember if she was also banned from the Schengen Area for some years but I think so.
I don't think that any visa is automatic, even for a bell ringer. It may be easy but there is always a person making the final decision.