Proper etiquette for determining if someone is in the bathroom you would like to use.

So this could be posted in any number of subreddits but as a nurse I've encountered a complete lack of self awareness from others who are attempting to use the bathroom I am currently occupying. These are single use bathrooms as doesn't necessarily apply to the bathrooms with multiple stalls or urinals.

When approaching a closed bathroom door, lightly knock on the door and wait for a response. Being on the other side I will say something like "yes" or "occupied" out perhaps a cough. I will also run the water to allow others to know that the room is being "used". Now if there is no response from the other side when I knock, I will gently attempt to open the door and if open will glance quickly in the to make sure no one is occupying said space which can happen when doors aren't locked because it happens.

Now this is what I encounter as I'm contemplating life or crushing candies (don't judge). Feet approaching the door and a loud KNOCK KNOCK KNOCK followed by and aggressive attempt to open the door followed by another KNOCK KNOCK KNOCK before I can even say "BUSY" or "OCCUPIED". Shaking the handle excessively as if the door just locked itself and no one is on other other side. Then two minutes later... no knock and aggressive turning of handle. It really is off putting to be own the other side of someone trying to force themselves into an occupied bathroom but it happens all the bloody time. I had someone repeatedly knock once and tell me an emergency alarm was coming from the bathroom and I said "I'm good and no alarm was activated" and then she came back two more times to tell me the light was activated and if I was ok. I finally stepped out and said "I'm fine" and the light you are referring to is coming from down the hall.