@lynnesbian Oh hey! I'm the person who originally submitted this to reddit.
As far as I know, this rule is no longer in place. It still shows up in some recent-ish documents (like [1]), but a train driver I know showed me a screenshot of a document explicitly stating that this paragraph was made obsolete.
It also doesn't show up in the current R 300.5 anymore. [2]
[1]: https://www.bav.admin.ch/bav/de/home/rechtliches/rechtsgrundlagen-vorschriften/fdv.html
[2]: https://www.bav.admin.ch/bav/de/home/rechtliches/rechtsgrundlagen-vorschriften/fdv.html
@draemmli @lynnesbian
Otoh, the German LZB linear train control is 8-bit to its core. One sector is up to 12.7 km long, 127 × 100 m loop sections, for signed 8-bit position counters.
@lynnesbian Whoops, link [1] was supposed to be this: http://eisenbahnberatung.ch/Dokumente_Web/R%20I-30111.pdf
@draemmli thanks for clearing this up! i managed to find a slightly more recent document mentioning it, but you're right, it seems to have disappeared now
@lynnesbian I think the original limitation was caused by mechanical counters with eight physical bits (so, not actually software), which have now been phased out.