My FPS when trains are stopped:

When I launch the trains (I think 7 in total) by addin missing rails path near the player FPS gradually goes down to an average of 19 and then stay in between 18.0 and 19.7
My FPS ~30 seconds after I have laucnhed trains (connected rails):

Quite surprising that such small amount of trains on a pretty simple rail network would cause so much lag.
PC specs: https://dl.dropboxusercontent.com/u/164 ... 20Spec.txt
All game options designed to increase FPS are turned on.