Vertical kink
Work in progress: This section is still a work in progress — content is being added and revised continuously.
What is checked? Does the grade change sign (uphill → downhill or vice versa) without a sufficient level section in between?
Why does it matter? At a crest or sag the car ends lift or dip abruptly — long, stiff vehicles lift their wheels (crest) or ground their couplers/skirts (sag), and couplings part “by ghost hand”. Prototype and model both ease vertical transitions; as a model rule of thumb a level section of two car lengths suffices (plus gentle run-ins, approximated with short track pieces on sectional track).
How to fix it: Insert a level section of at least two car lengths; additionally ease the ramp ends with short pieces (entry/exit easing ≈ one car length).
Numbers & defaults: level section ≥ 2 × longest car (H0 default: 528 mm).