FA-67068 / Railway interlocking logic / Member archive

ATP braking curve supervision: line speed ceiling · case 03

The permitted speed exceeds the line speed far from the target.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Permitted speed at the train is sqrt(vt^2 + 2*a*d) with vt the target speed in m/s, a = decel_cms2/100 m/s^2 and d = max(distance - safety margin, 0); convert back to km/h, truncate to an integer (never round up) and cap at line speed. Action is brake if speed > permitted + brake margin, else warning if speed > permitted + warn margin, else none.

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: curve above line speed	`{"action": "none", "permitted": 210}`	`{"action": "brake", "permitted": 120}`	Failed

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