Saishuu Chikan Densha
English name: Midnight Sleazy Train
Genres: Hentai
Type: OVA, Episodes: 3
Aired: Sep 25, 2002 to Feb 25, 2003
Studio: T-Rex
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
In a crowded train, strangers are likely to end up being too close for comfort. But for some people, being too close is a comfort. When a poor conductor witnesses the bizarre yet inviting ritual of anonymous train sex, he jumps on the opportunity to turn it into a business. Every night after the midnight train ends its route, he turns it into a rolling bordello. Get ready to climb aboard... the sleazy train is coming. 

(Source: ANN)