In a city as large as New York, we are blessed with many nerds and a number of obsessed New Yorkers with a passion for the minutiae of city life. I say blessed, because how else would you learn about the horrors of certain trains using mixed fonts in the Do Not Lean on Door signs? The primary font in the subway system is Helvetica - see Train of Thought, my story of June 9, 2010, about subway fonts and other obsessions, such as H I K O P T U X Y.
It was noticed by some, however, that there were a number of trains where signs were actually using a mixture of fonts. Apparently, the possible dangers of falling out of trains or any other obvious reasons for not leaning on (and blocking) subway doors is secondary to the nuances of typography. In a 2009 Gothamist article about this discovery, a war of words in the comments section reveals this gem:
I noticed these when the R160s were new. I wanted to take my copy of Massimo Vignelli's 1970 New York City Transit Authority Graphics Standards Manual and thwack someone over the head with it, but that wouldn't be a good idea since I might damage a valuable book.
Regulations like Do Not Lean on Door mean very little in New York City. Often, all available seating is taken and with trains lurching, leaning, and stopping abruptly, riders who are standing need to stabilize themselves. Holding onto vertical or overhead poles for extended periods is tiring. Leaning against exit doors becomes a preferred resting spot for many, with each individual door just right for one person. The eight doors (4 pairs per car) become coveted spots.
Like jaywalking, these regulations are virtually never enforced. The signs do provide many functions however - a good opportunity for study of fonts, a record of unenforced policies, a clean surface to lean against, a chance to display requisite New York City Street Cred and attitude, and an opportunity for the less courageous for an act of defiance which will assuredly go unpunished. A sign and siren for the amateur lawbreaker and Aspiring Rebel :)