FA-67003 / Railway interlocking logic / Member archive

Level crossing warning timeline: crossing proving point · case 03

A four-quadrant crossing is proven before its exit barriers are down.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Strike-in at t0 starts amber; red follows 3 s later; entrance barriers are down 4 s after red plus lower_s; exit barriers 4 s after that. Half-barrier crossings are proven at entrance-down, four-quadrant crossings at exit-down. Train arrival is t0 + floor(distance*3.6/speed). The protecting signal clears at max(proven, obstacle clear) and never without an obstacle confirmation (None). warning_ok needs arrival-red >= min_warning_s and a clear time no later than arrival - sighting_s.

Why this case matters

Interlocking logic decides whether trains may be given authority; a wrong decision at this point either grants unsafe movements or strands traffic.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: four-quadrant proving	`{"arrive": 80, "proved": 15, "signal_clear": 25, "warning_ok": true}`	`{"arrive": 80, "proved": 19, "signal_clear": 25, "warning_ok": true}`	Failed

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