This regulation is so vaguely written by the FAA as to being meaningless. Speaking from experience operation a restricted category aircraft ( duster), we run into these three “restrictions” all the time. One fsdo’s definition of densely populated is not the same as anothers. Same goes for a busy airway. As for pasenger carrying airport, every airport that has a guy giving his neighbor a ride, is a passenger carrying airport. These so called restrictions were designed to be vague for the specific purpose of giving the feds legal latitude in case of an incident.

I can tell you practically speaking they are ignored.