When I replaced city road with else road, graphics changed - but not speed. So it called me speed 50 km/h for road where it should call speed 130 km/h.
I always thought this was a feature, and not a bug, because it also happens in older versions of Simutrans. You need to destroy the city road and rebuild the new road to get the higher speed.
I was used to statement you described - regardless of I think it is not right.
... but in 4180 this behavior was not present. There you could build road of higher quality and it got right speed of that road you built - like it should be. Outside of cities it is irrelevant (it means that there city roads can be destroyed and then replaced by new one) - but inside cities it would be really good if this would be changed back to statement of 4180.
Imho nothing has changed with respect to this behavior in the recent past.
Then it is very strange - and bug in 4180. But as I wrote, It would be good if replacing of city road with road of higher quality would be complete - it means also with change of speed.
I think the current way is better.
It's unusual to have a +70km/h road inside the city, unless on a different grade, usually an elevated highway.
AEO: Of course. I often use tunnels for roads for lines where I need higher speed - instead elevated ways. It is a little better.
Full rebuilding of city roads is important mostly for roads what appeared inside city limits area but they are still quite distant from city, itself.