@crimsonmote try using a map size larger than small

Of course one can aim at 1:1 scale. But then not until the game can allow hundreds of kilometers of maps, the possible size of maps is just too small, not even close to being large enough for a metropolitan area. So it beats the purpose: what's gonna be the point of having industries and high speed rail?
The scaling problem in the game is so severe and it affects everything. Capacity, population, parameters and mechanisms are designed from ground up to have scaling in mind. Still it is severely out of proportion. For example, when you want a map to represent hundreds of kilometers, literally the long station needed for long enough high speed or commuter trains you need covers half a city.

While I understand the math behind what you are doing, I agree with GaftLukas that most maps are scaled. Playing country sized maps, I find that the curves already need to be way larger than the scaled distance between major cities would indicate.
I have have actually thought that the curvature penalties should be reduced or possible have a modifier that comes from the specific map to represent ground scale.

It all depends on how you build. You can aim for 1:1 scale.

@GrafLukas Agree. Acceleration and curve limits are out of scale. It should be faster.

No doubt this is interesting. However, since the game is scaled, I'm not sure this adds realism. It is annoying enough that in the campaign alone the train hardly reached it max. speed ever in the Japan or the Germany scenario, even though the cities are very very far apart. Same is true for custom maps - on a London to Oxford nonstop run, a speed of more than 100mph is in reality no problem. On most maps in the game this is impossible, though.

I think what the game actually needs is a boost of accelleration and curve speed, rather than a buffer, or some possibility to link this to the scale - take the average distance between two of the larger cities on the map and make sure the trains can reach 100% speed in less than 1/3 of that distance.

Vanilla game values are much much faster than they should be. In this picture [ibb.co] axis X is curve radius and axis Y is speed in meters per second. Blue line represents default game values, green line represents moded not superelevated values and pink one are superelevated values.

Interesting, and how are the results compared to the standard game values? Faster, slower, other differencies?