I'm not sure, if it is necessary to define separate sets of freight/passengers/shunters by means of 0 cargo type,
in reality such engines are used without distinction, maybe except express passengers.
But large shunters or freight locomotives are common used for passengers trains (there is no heating issue because most USSR carriages have individual heating AFAIK), lets give user oportunity to decide what locomotive to use.
Unfortunately there are no CBs to control it
I was refering to retire_early - if vehicle life is 40 years, model life should have retire early period about 30 years.
For example, there is small tender locomotive 'klop', it dissapear from menu before diesel 3-axle shunter is available,
therefore I should be able to buy some steam shunters and keep them for future use without loosing maximal reliability.
What form do you intend? I can't find anything about it in the Ikarus set I have
Version 6 have green/yellow/red string refering to fast/medium/slow loading time and long/medium/high aging rate.
I'm not sure how those numbers are defined for xUSSR set - based on real parameters or just magic,
but if you are interested, I have proposal of macro to define it basing on doors number, (non)compartment etc.
Early freight wagons were also found (on photos) in the passenger trains. That means they were used with the speed of the fast passengers trains - up to 120 km/h. We understand, that was not common, but because it happened, we decided to allow it in the set too.
I doubt that ordinary plain bearings allow speed above 80 kmph in case of heavy freight wagons. 120 kmph is for modern rolling bearings.
It is possible, that there were some designs for fast reefers or covered cars for express cargo, but gondolas and flat cars have probably limited speed and mixed passenger/freight trains was not very fast.
From gameplay point of view, some freight cars should have limited speed to promote use of some freight locomotives, instead of using passenger locomotives for both passenger and freight trains.