Thank you very much for reporting this. I am afraid that I cannot reproduce the issue that you describe, however: the Class 172/0 (with three carriages) will reduce its speed to 93km/h on an 8 tile corner such as this, which is the correct speed for a curve with a radius of 1,000 meters according to the formula here
, and an 8 tile radius curve at 125m/tile is indeed 1,000 meters in radius.
The Class 172/0 travelling at 120km/h through the corner would be a bug, but note that it will only slow down when it reaches the second
of a pair of 45 degree corners, as it cannot know the radius of the corner until it has passed two 45 degree turns.
Can you upload a saved game in which the issue of the Class 172/0 travelling at 120km/h around an 8 tile corner can reliably be reproduced?Edit
: I should note that curve radii based speeds have not been abolished: what was abolished was the old system of having a corner speed limit based on the speed of the underlying way. That there cannot be a shallower turn than 45 degrees is accounted for by the fact that the vehicles will only slow down on the next
45 degree turn, based on an inferred radius taking into account the two different turns and the space between them, which might be a radius so large that there is no reduction in speed at all.