Dear Dumb Runner,
Is it OK to knock on someone's door if I really, really have to use the facilities? Emergency purposes only, of course.—Brandon
I assume that by "facilities" you mean "bathroom." And that by "emergency" you mean "shitting ASAP." If that's the case, my first advice would be for you to stop beating around the bush. Just come out and say it: I really, really have to use the bathroom. For shitting. When your bowels are about to erupt, there's no time for highfalutin euphemisms.
Anyway, in a bathroom emergency—i.e. when evacuation is imminent, and you and your body both know it—you have one of two choices. You can ruin your pants, or you can pull them down. Ruining your pants is seldom truly a choice, though, is it? So that leaves pulling them down, and the sooner the better.
For a runner mid-run, this usually means ducking behind some bushes or something—whatever's nearby that affords a reasonable level of privacy.
Ideally, of course, it would mean ducking into an actual restroom. In Japan. They have fantastic bathrooms in Japan. Very clean, very high-tech. But emergencies have a way of happening at inconvenient times and in inconvenient places—like the residential neighborhood you allude to in your note. In these cases, you really are in a pickle—there are lots of prying eyes, and any bushes tend to belong to the owners of those eyes.
Yes, you could knock on someone's door. But I would advise against that. Unless you chance upon an insanely nice and unbelievably trusting person, the best you could hope for is an awkward, "Sorry, no." The worst would be a paranoid gun enthusiast who's just watched a cable news documentary on home invasions. Or a guy with a dry well in his basement and a healthy supply of lotion and baskets.
Not worth it.
And yes, I understand that this may leave you no choice but to squat behind the nearest tree. You've gotta do what you've gotta do.