It's a perfectly flat straight section, so I wonder why there is a 70km/h speed limit near Jeßnitz on Rapid Transit.
I don't know why exactly there, but sometimes speed restrictions on perfectly flat sections happen due to initiatives against noise pollution. So if there is a village or some kind of wildlife/forrest sanctuary, speed restrictions can be a thing. Maybe that's the reason.
There's similar of Hamburg Lubeck where due a weak old bridge the limit drops you from 160km/h to 90km/h (or it could even be 80km/h, although that just be because of PZB kicking in). Its things like this which makes route knowledge so important and when accurately modelled in the game adds to the immersion and makes it challenging (especially when driving no HUD).
Actually, there is a route in Southwest Germany where you have to slow down to 40 or 25 due to the way 1 single level crossing is set up. On a mainline.
What's so special about this level crossing? I believe it's not uncommon for German level crossings to have a higher speed limit, is it?
The speed restriction of a level crossing in germany depends on the way it is maintained and the infrastructure status. If it is automatic and operated automatically, there is no speed restriction. In this case the level crossing isnt modernized and also had some incidents over the past years.