I work at a smallish (30 something person) company based in NYC. The office consists of 2 floors, with most of the engineers on the first floor and the executive staff on the second. Due to the construction of our office, there is are only two bathrooms on the first floor, and a single bathroom on the second floor. The bathrooms on the first floor are gender specific, whereas the second floor bathroom is not. Additionally, the second floor bathroom is single person, whereas the first floor bathrooms have space for multiple people to be in them at one time. However, there is only 1 toilet available in the mens bathroom. The vast majority of our staff is also male. This means that there are around 25 men on the first floor that need to share the first floor bathroom. There are no rules against engineers on the first floor using the upstairs bathroom, but it is quite awkward as it is clearly setup for use by the executives and a particular executive who sits in front of the second floor bathroom has a penchant for making poop jokes, exacerbating any embarrassment regarding the use of the bathroom.
I provide all this context to explain my issue. I have a particular male coworker who will take extended periods of time (around 15 minutes or so) in the bathroom, occupying what is effectively the only toilet. I frequently use this toilet and make a point to get in and out as quickly as possible, as a courtesy to my other colleagues. While I absolutely understand that this person enjoys spending their time in the bathroom (as I do at home), it's pretty rude to occupy what is an essential resource for the other staff. Personally, I've had to wait quite uncomfortably for some period of time for this fellow to leave the bathroom. What can I do to alleviate this issue without confronting this person in a rude manner?