New York City Transit Authority Graphics Standards Manual
In 1970 the New York City Transit Authority released this brand identity manual designed by Massimo Vignelli and Bob Noorda of Unimark International. Pentagram recently tweeted that it was found in a locker under some old gym clothes, and that their employees Niko Skourtis, Jesse Reed, and Hamish Smyth have created an online archive: thestandardsmanual.com where the book can be seen in its entirety.
Further Reading
The (mostly) true story of Helvetica and the New York City Subway