A train will stop 20m short of a trackmarker, if your train is speeding at a high rate, it might slide right on through a trackmarker that takes AI by suprise ...so you would need to slide the trackmarker backwards to get the train to stop earlier ... and too, place ever slower incremental speedboards to slow a train from down from120km ... to 60 km, to 30km, to 15km to make more gradual stops.
I know some excellent imperial, and metric speedboards, some are invisible in driver.
A train traveling down a steep slope, may not be able to stoop completly, and may continue to slide, with it's wheels locked up.
A train will immediately slow by seeing a lower speedboard ... but will only speed up to a higher speedboard, once the last car passes.