This doesn't seem like it's at all close to happening, but the Daily News reports that the MTA is at least looking into the possibility of someday erecting screen doors along the edge of subway platforms as a way to prevent straphangers from falling or jumping on the tracks, which seems to happen way too often. According to a probably mostly accurate list on Wikipedia, you may have experienced these screens already if you've taken the subway recently in Tokyo, Kyoto, Osaka, Nagoya, Yokohama, Kobe, Fukuoka, Sapporo, Sendai, Seoul, Busan, Daejeon, Daegu, Incheon, Gwangju, Dubai, Hong Kong, London, Taipei, Kaohsiung, Beijing, Tianjin, Shanghai, Guangzhou, Shenzhen, Chongqing, Kuala Lumpur, Singapore, Bangkok, Copenhagen, Paris, Rennes, Toulouse, Lille, Torino, St. Petersburg, Barcelona, Seville, or São Paulo.
But here's what they look like in the London Tube if you haven't seen them.
Cool! This would undoubtedly save dozens of lives a year! So what's the holdup? Oh, right the hundreds of millions of dollars that the MTA is not even close to having.