The game suffers from several typical “newbie” mistakes. Mostly around the UI, but not always. It overuses the ‘render to texture’ feature. That one is slow as hell. Most games will grudgingly use one or two RtR viewports. TF will happily open 100 of such windows. Another issue lies with, what 3D programmers call “batch count”. Generally, the usage of 3d API is not optimized, making too many heavy rendering calls for trivial issues. You can see this in, for example, line management window. Just go to any corner of the map, look away from the map, where you get a very high frame rate, and open the line manager.
I get a drop from 60fps to 40fps in such case. That is appaling.
The simulation part of the game does not seem to all that slow, to be honest, its the graphics part that pulls it down.