This a probably an episode of Twilight zone or Tales of the unexpected, Alfred Hitchcock presents or similar series. Definitely from 80's-90's. Color, not black and white.
There was this man that was obsessed with making model trains and railways. His neglected wife was growing more and more jealous of this hobby until she decided to pick it up, too. This started a rivalty between the two. Finally the wife electrocuted the husband and buried him inside a huge landscape railway model. When the police arrived they started playing with the trains and the train got stuck in a tunnel. When they reached for it, they pulled out husbands hand. At the end the wife was in a (the) train and entered a tunnel.
Do you know this movie/episode?
Edit: So far it's not "Track 29", nor "So You Want a Model Railroad"