FA-66854 / Railway interlocking logic / Member archive

Route request admission: opposing detection scope · case 04

Routes in the opposite direction anywhere on the layout block each other and opposing routes are misreported.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

x has a route table (sections, overlap sections, required point positions, direction), the locked routes, occupied sections and a requested route. Return unknown-route, already-set, occupied (any path section occupied), opposing:<r> (shared path/overlap with an opposite-direction locked route), section-conflict:<r>, point-conflict:<r> (a shared point needed in the other position) or granted. Locked routes are examined in sorted order. Overlap may overlap another overlap.

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: opposite direction elsewhere on the layout	`"opposing:S8-S6"`	`"granted"`	Failed

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