TIL the director the French Connection paid an official at the New York Transit Authority a $40,000 bribe to overlook the rules and allow the famous chase sequence to be filmed.

http://www.wnyc.org/story/htt-william-friedkin/

https://www.reddit.com/r/todayilearned/comments/15l067m/til_the_director_the_french_connection_paid_an/