This is a subject that has been studied quite a bit, as there are a bunch of jobs where people have to monitor for rare emergencies, and react fast if an emergency should arise. Things like pilots on flights with autopilot; lifeguards watching for swimmers in distress; CCTV monitoring; operating airport X-ray machines, and so on.

One such study is "Performance consequences of automation-induced 'complacency'" (Parasuraman, Molloy & Singh, 1993) https://www.pacdeff.com/pdfs/Automation%20Induced%20Complace...

Previous studies had found that a human and a computer performed markedly better than either a human alone or a computer alone - but in those studies failures were quite common, so they didn't give the humans time to get bored or distracted.

When researchers got test subjects to perform a simulated flying task, monitoring a system with 99%+ reliability, they found the humans were proportionally much worse at stepping in than they were on less reliable systems.

Swimming pool lifeguards will often change posts every 15-20 minutes and and get a 10-15 minute break every hour, to keep things interesting enough that they can pay attention. Good luck getting drivers to do that.