Sorry, it was _just_ the removal of the conductor (the one in the middle of the train that opens and closes the door. That was enough to scare people. They did it in 2005 and tried again in 2009.

http://www.nytimes.com/2005/06/20/nyregion/on-l-train-driver...

http://www.nydailynews.com/archives/news/conductorless-train...

http://nymag.com/daily/intelligencer/2009/02/subway_riders_s...

The plan was to take out even the operator, but unions kept the train operator in. http://www.nytimes.com/learning/teachers/featured_articles/2...