I had been hoping to attend the Presidential Inauguration next week since it is in my backyard (DC is 95 miles from my house, and I have the option of taking a train part or all of the way). But since predictions for the number of people attending the inauguration events keeps climbing, I decided to stay home. Particularly since the last estimate I saw predicts that I95 will back up all the way to Richmond, meaning that I shouldn’t bother to even leave my house.
But more recent predictions by crowd experts indicate that predicted estimates are usually grossly inflated. After all, many people want to see a historically high turnout for the inauguration. Bigger is better, and big estimates signify the importance of the event in our culture.
Predicting the number of people who can attend the inauguration is a science, and it can be determined by asking these three questions, according to crowd expert Clark McPhail:
- What is the square footage of the available public space?
- What proportion of that space is occupied?
- What is the density ratio of that occupation?
McPhail indicates that simple geometry and points of view cause bad crowd estimates:
Large gatherings are usually more densely packed at the front and middle than at the back or sides. Estimates made from the front of the gathering and from a vantage point at or near ground level are victim to the perceptual illusion that the entire gathering is as densely packed throughout as it is at the front. This leads to the erroneous conclusion that the gathering is much larger than it more accurately appears when viewed from overhead. Organizers on a stage, looking at the gathering spread out before them, often fall victim to this illusion. So do inexperienced police observers and journalists.
The National Park Service is planning on having 5,000 portable toilets available on Inauguration Day. (I found this interesting, since I am no stranger to portable toilets–I reluctantly use one before every race I run. They key difference is that everyone goes to the bathroom at the same time before a race, where bathroom usage is likely more random at the Inauguration.) If one million people show up for the Inauguration, then there is one toilet for every 200 people and if four million people show up (the current inflated estimate), then there is one toilet for every 800 people. As Carl Bialik writes for WSJ, this is likely way too few toilets:
The New York City Marathon last November had one toilet for every 17 runners. The U.S. Army’s standard is one commode for every 25 males and one for every 17 females, according to Albin Majewski of the Army’s material systems directorate. And the International Code Council requires one toilet for every 40 people at nightclubs, and more than one for every 50 people in an office building.
Yeah, there is definitely some potty-parity going on. The average time spent in public restrooms is 47 seconds for men and 79 seconds for women. Most researchers find that women take about 70% longer in the bathroom and need more toilets. Bathroom science is fascinating.
So, now I don’t know what to do for Inauguration Day. I want to attend the Inauguration (and it looks like I’ll be able to make it if I take the train). But I’d also like to use a bathroom at some point during the day.
January 13th, 2009 at 10:50 am
You know, I still say go . . . Just seems like a good chance that this inauguration shouldn’t be missed.
January 13th, 2009 at 7:54 pm
As sales rep to a leading porta potty rental company, I went to my handy dandy user calculator to see what it predicts is needed for an event like this and the number is something like 20,000 toilets and they should be pumped every 8 hours!
The Porta Potty Queen
Potty Rentals Good Enough For Any President
January 14th, 2009 at 6:58 am
Go … but don’t drink too much before you go!
It is interesting to see the figures that you quote for bathroom science. There was an amusing paper which touched on the subject in:
A quintet of queueing quirks
(Mathematics Today (2000) 36, 2: 38-40)
Robert Matthews (1University of Aston, Aston Triangle, Birmingham B4 7ET, UK)
With its probabilistic roots, queueing theory offers a promising hunting ground for surprising and counter-intuitive results. The author highlights five such results that emerge from elementary queueing theory, and shows how they cast light on several long-standing issues, such as ‘Murphy’s Law of Queues’ and the length of queues at public toilets.
Matthews quotes differing mean times, (slightly less for men) and pointed to the relevance of provision in theatres where the usage peaks during the interval. Back in the 1970’s, the Operational Research Quarterly (I don’t have the reference to hand) described a study to find the mean times, and the problems of measurement without invading privacy or affecting the results.