Interesting that it uses 20 minutes. I guess that's optimistic if you need to account for delays, but that's much longer than I often take to transfer (5 minutes often being workable if the trains are generally reliable, and you're able to catch a later train if you miss the intended one).
Swizerland (SBB) has some nice data on this with 98.9% connection punctuality, 40% of connections <5min and 77% under 10min. Though they might be an outlier here given the integrated timetable.
Indeed the 20 minute interchange assumption interacts quite badly with Swiss schedules, because actual Swiss interchanges are routinely much tighter than that, so each is penalized with 30 or 60 minutes extra for the next connection.
It depends on the station. If you're in Leipzig Central and you need to switch from platform 20 to platform 6, 5 minutes is very stressful because of the sheer number of platforms you need to walk past.
> In reality there is a train e.g. every hour or so, or even none at the same day
That really depends on your route. Some busy lines in the UK have trains every 30 minutes, 15 minutes or even 10 minutes. Across London, it might be every 5 minutes or even every 2.
