tricia
Conductor
That works too; I was just thinking they'd be locked by default so only the passengers booked could access. No system will please everyone. Using a PIN system eliminates the need for physical keycards, but some passengers may have trouble keeping track of their PIN. On the other hand passengers may forget to take their keycard with them to the diner/toilet/shower and lock themselves out anyway. Letting passengers use their phone as a key raises issues of its own, and would still need a backup option. The SCAs presence should alleviate lockouts.
Any system where the door locks with the key left behind in the room is going to have the SCA up all night opening doors for sleepy passengers who walk down the hall to the bathroom without their key. Not a good scenario.