the source everyone reports for this PDF is gone, and it's not exactly easy to find swiss train law documentation when you don't even speak german
but here's a current link: https://www.hech.ch/wp-content/uploads/2018/07/I-30111_09122018_Anhoerung.pdf
page 123, section 4.8.4 "Zugbildung"
German is a good language. any language that has a single word that means "a face in search of a backhand" is a good language.
@firstname.lastname@example.org's anti-chud pro-skub instance for funtimes