FA-66954 / Railway interlocking logic / Member archive

Sectional route release: fault latch · case 04

Release resumes after a track circuit clears without having been occupied.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Sections of a locked route are released in route order as the train passes. A section is released when it clears, it was seen occupied earlier, its predecessor is already released (or it is the first), and the next route section is currently occupied (or it is the last). A clear of a never-occupied route section latches a fault that stops all further release. Events for sections outside the route are ignored. Output released sections in release order and the fault flag.

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: phantom clear on first section	`{"fault": false, "released": ["T1"]}`	`{"fault": true, "released": []}`	Failed

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