FA-66937 / Railway interlocking logic / Member archive

Approach locking time release: set admission · case 02

Setting a route clears an active approach lock early, or a route cannot be set for an approaching train.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

A route can be set only when free. pass_signal moves a set route to in-use; train_clear frees an in-use route. Cancelling a set route frees it at once unless a train is in the approach section, in which case it is approach-locked until cancel time + release_s (released when an event time reaches the deadline). approach_occ/approach_clear track the approach section. query appends set, free, in-use or locked-until:<t>.

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: set attempted while locked	`["set"]`	`["locked-until:62"]`	Failed

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