The London Post Office Railway ran from 1927 until 2003 shuttling mail between eight sorting offices. The system, inspired by the Chicago Tunnel Company, ran driverless trains between the stations soley for the purpose of sorting mail. In 2003 at the end of service, only three stations remained. The other stations closed because the sorting offices above them had been relocated. Service was given up in favor of trucks because it is said that operating the railway is 3-5 times more costly than using trucks. The railway carried over 4 million parcels during each of its 19 hour days. The line was 6.5 miles in length and very successfully solved the problem of transporting large volumes of mail quickly across a capital city.
Further Reading: http://www.mailrail.co.uk/ http://mikes.railhistory.railfan.net/r023.html Wikipedia
Information About Closure: http://www.guardian.co.uk/uk_news/story/0,3604,940742,00.html http://www.thisislocallondon.co.uk/news/topstories/display.var.301893.0.final_delivery_for_mail_rail.php
While checking out the Zeitgeist on ReConnectingAmerica.org, I found this amazing video of a fancy staged dinner party on the London Underground (see video below).