The beginning of a mini-marathon

Benjamin Franklin Boulevard, cutting from City Hall all the way up to the Art Museum, is normally a main feature in any Philadelphia bike or foot race, and usually represents either the first or the last stretch of concrete that the athletes must tread. You can often tell when the city is gearing up for a weekend of racing by one major sign: blue port-a-potties appear lined up neatly on either side of the street, boxy and patient, like colorfully dressed soldiers waiting for orders. There are sometimes a few, sometimes hundreds of them, secured by little plastic locks, shiny and clean, reporting proudly for duty. Every time I see them lined up, I always have the same reaction, and the same conversation with myself: Firstly, I can't imagine why there is a need for so many of them - surely all the athletes won't need a potty all at the same time - then I reason that maybe there's a certain capacity the potty can reach, so that once, say, 20 people have used it, it's gone from decently clean to disgusting to absolutely unusable, and whatever it is inside the potty that holds all that unpleasant stuff is at a dangerous capacity. At that point, there would be a need for the next potty, so that the next 20 people can use it. So the port-a-potty company might figure, if you saturate the area with potties and there are lots of potties to choose from, different folks will choose different ones, reducing the probability of one potty going bust to a safe recess. I then try not to think about the process of cleaning all of those potties, and the poor people who have the job of doing it. Who knows. I suppose, though, if I ever do run that marathon, having a new, clean potty to use at the end of the race will be all the more incentive to cross the finish line sooner.