If you have a digital copy of the movie and need a separate .srt file, you can search reputable community libraries. Popular sites for English subtitles include:
If buying the film, ensure the specific edition includes English subtitles: Terror Train (4K UHD) - Kino Lorber Home Video Terror Train titlovi Engleski
Known for having a vast catalog, including rarer older films. If you have a digital copy of the movie and need a separate