it would be intersting to know what the gradient actually are in this game. maybe one of the devs who reads this can shed some light onto it?
if we presume that the height contours are spaced in a logical manner of say 5 or 10 m of height, we might roughly calculate the gradient according to phytagoras from the building costs of track.
just the track costs 50 moneys per metre, with the steepest incline it costs 6800 moneys to go straight from one contour line to the next, which equates to 136 metres. according to phytagoras that makes either 2,1 or 4,2 degree depending on whether the height lines are at 5 ot 10 metre intervals. that again equates to an inclination of either about 3,6 or about 7,4 percent for the steeper gradient. from the looks of it, i would think it is the steeper one.
its abvious however, that even though tractive effort is considered by train fever, it seems not to be calculated 1:1 to real physics. even a strong modern electric is not able to pull too many wagons up a gradient of 3,6 percent, let alone one of 7,4.