FAILURE MAP
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FA-66981 / Railway interlocking logic / Open access

Track circuit pick-up delay: pick-up delay boundary · case 01

A section stays occupied one sample longer than its pick-up delay.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The accumulated unshunted time must strictly exceed the delay.

THE FAILURE

The accumulated unshunted time must strictly exceed the delay.

Unsuccessful approach: Measuring from the first unshunted sample as time zero still delays clearance by a period.

Case contract

Samples arrive every period_ms: True is shunted, False unshunted, None a power or receiver failure. The section starts occupied. A shunt or a failure makes it occupied immediately and restarts the pick-up count; it becomes clear once consecutive unshunted samples span at least pickup_ms (count*period_ms >= pickup_ms). Output the state after every sample.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    state = 'occ'
    run = 0
    out = []
    for s in x['samples']:
        if s is None or s:
            state = 'occ'
            run = 0
        else:
            run += 1
            if state == 'occ' and run * x['period_ms'] > x['pickup_ms']:
                state = 'clr'
        out.append(state)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: pick-up exactly at the delay', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False]}, ['occ', 'clr', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('boundary: never clears', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [False, False, False]}, ['occ', 'occ', 'occ']), ('control 1', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, False, None, False, False, True, False, True, False, None, None]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 4', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, False, False, True, True, False, False, True, False, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 7', {'period_ms': 100, 'pickup_ms': 500, 'samples': [False, False, True, False, None, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('sampled regression 18', {'period_ms': 250, 'pickup_ms': 500, 'samples': [True, None, False, False, None, False, False, False, False, False, False, False, None, False]}, ['occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ']), ('sampled regression 6', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, True, False, False, None]}, ['occ', 'clr', 'clr', 'occ', 'occ', 'clr', 'occ']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('control 12', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, True, False, False, None, None, False, True, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 15', {'period_ms': 250, 'pickup_ms': 750, 'samples': [False, False, True, True, None, True, None, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('sampled regression 21', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, False, False, False, False, True, False, False]}, ['occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'clr'])], [('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('sampled regression 55', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, None, None, False]}, ['occ', 'clr', 'clr', 'occ', 'occ', 'occ']), ('sampled regression 19', {'period_ms': 100, 'pickup_ms': 500, 'samples': [False, True, False, False, False, False, False, False, False, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'occ']), ('boundary: never clears', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [False, False, False]}, ['occ', 'occ', 'occ']), ('regression: train arrives on a clear section', {'period_ms': 100, 'pickup_ms': 100, 'samples': [False, True, False]}, ['clr', 'occ', 'clr']), ('control 23', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, None, None, False, True, False, True, False, False, None]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 26', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, None, False, False, True, None, None, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 29', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, True, False, False, False, True, True, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('sampled regression 77', {'period_ms': 250, 'pickup_ms': 500, 'samples': [None, True, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'clr']), ('control 37', {'period_ms': 250, 'pickup_ms': 300, 'samples': [False, True, False, False, False, False, False, False, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'clr']), ('regression: pick-up exactly at the delay', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False]}, ['occ', 'clr', 'clr']), ('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('control 34', {'period_ms': 250, 'pickup_ms': 300, 'samples': [True, False, False, False, False, False, False, True]}, ['occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ']), ('control 40', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, None, False, False, False, False, True, None, False, False, None, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 43', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [True, False, None, None, False, False, True, False, None, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: train arrives on a clear section', {'period_ms': 100, 'pickup_ms': 100, 'samples': [False, True, False]}, ['clr', 'occ', 'clr']), ('sampled regression 3', {'period_ms': 250, 'pickup_ms': 750, 'samples': [True, False, False, False, False, False, False, False, True, True, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('sampled regression 60', {'period_ms': 100, 'pickup_ms': 300, 'samples': [None, False, True, False, False, False, False, None, False, None, None, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'occ']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('sampled regression 45', {'period_ms': 250, 'pickup_ms': 500, 'samples': [True, False, False, False, True, False, None, False, False, None, True, False]}, ['occ', 'occ', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'occ']), ('control 48', {'period_ms': 250, 'pickup_ms': 750, 'samples': [False, False, True, True]}, ['occ', 'occ', 'occ', 'occ']), ('control 51', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, None, True, False, False, False, True, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: pick-up exactly at the delay['occ', 'occ', 'clr']['occ', 'clr', 'clr']Failed
regression: receiver failure on a clear section['occ', 'occ', 'occ', 'occ']['occ', 'clr', 'occ', 'occ']Failed
regression: bobbing shunt while occupied['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'clr']Failed
regression: receiver failure mid pick-up['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'clr']Failed
boundary: never clears['occ', 'occ', 'occ']['occ', 'occ', 'occ']Passed
control 1['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed
control 4['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed
control 7['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed

SHA-256 / f4c3751e3a8f9e84f98ee412066845ef8dbe1be27581b7a052cbbba0ab859336

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    state = 'occ'
    run = 0
    out = []
    for s in x['samples']:
        if s is None or s:
            state = 'occ'
            run = 0
        else:
            run += 1
            if state == 'occ' and (run - 1) * x['period_ms'] >= x['pickup_ms']:
                state = 'clr'
        out.append(state)
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: pick-up exactly at the delay', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False]}, ['occ', 'clr', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('boundary: never clears', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [False, False, False]}, ['occ', 'occ', 'occ']), ('control 1', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, False, None, False, False, True, False, True, False, None, None]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 4', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, False, False, True, True, False, False, True, False, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 7', {'period_ms': 100, 'pickup_ms': 500, 'samples': [False, False, True, False, None, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('sampled regression 18', {'period_ms': 250, 'pickup_ms': 500, 'samples': [True, None, False, False, None, False, False, False, False, False, False, False, None, False]}, ['occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ']), ('sampled regression 6', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, True, False, False, None]}, ['occ', 'clr', 'clr', 'occ', 'occ', 'clr', 'occ']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('control 12', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, True, False, False, None, None, False, True, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 15', {'period_ms': 250, 'pickup_ms': 750, 'samples': [False, False, True, True, None, True, None, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('sampled regression 21', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, False, False, False, False, True, False, False]}, ['occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'clr'])], [('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('sampled regression 55', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False, None, None, False]}, ['occ', 'clr', 'clr', 'occ', 'occ', 'occ']), ('sampled regression 19', {'period_ms': 100, 'pickup_ms': 500, 'samples': [False, True, False, False, False, False, False, False, False, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'occ']), ('boundary: never clears', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [False, False, False]}, ['occ', 'occ', 'occ']), ('regression: train arrives on a clear section', {'period_ms': 100, 'pickup_ms': 100, 'samples': [False, True, False]}, ['clr', 'occ', 'clr']), ('control 23', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, None, None, False, True, False, True, False, False, None]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 26', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, None, False, False, True, None, None, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 29', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, False, True, False, False, False, True, True, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('sampled regression 77', {'period_ms': 250, 'pickup_ms': 500, 'samples': [None, True, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'clr']), ('control 37', {'period_ms': 250, 'pickup_ms': 300, 'samples': [False, True, False, False, False, False, False, False, False, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'clr']), ('regression: pick-up exactly at the delay', {'period_ms': 250, 'pickup_ms': 500, 'samples': [False, False, False]}, ['occ', 'clr', 'clr']), ('regression: bobbing shunt while occupied', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, True, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('control 34', {'period_ms': 250, 'pickup_ms': 300, 'samples': [True, False, False, False, False, False, False, True]}, ['occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ']), ('control 40', {'period_ms': 100, 'pickup_ms': 1000, 'samples': [False, False, None, False, False, False, False, True, None, False, False, None, True]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('control 43', {'period_ms': 250, 'pickup_ms': 1000, 'samples': [True, False, None, None, False, False, True, False, None, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])], [('regression: train arrives on a clear section', {'period_ms': 100, 'pickup_ms': 100, 'samples': [False, True, False]}, ['clr', 'occ', 'clr']), ('sampled regression 3', {'period_ms': 250, 'pickup_ms': 750, 'samples': [True, False, False, False, False, False, False, False, True, True, False, True, False, False]}, ['occ', 'occ', 'occ', 'clr', 'clr', 'clr', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']), ('sampled regression 60', {'period_ms': 100, 'pickup_ms': 300, 'samples': [None, False, True, False, False, False, False, None, False, None, None, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'occ']), ('regression: receiver failure mid pick-up', {'period_ms': 100, 'pickup_ms': 300, 'samples': [False, False, None, False, False, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'clr']), ('regression: receiver failure on a clear section', {'period_ms': 100, 'pickup_ms': 200, 'samples': [False, False, None, False]}, ['occ', 'clr', 'occ', 'occ']), ('sampled regression 45', {'period_ms': 250, 'pickup_ms': 500, 'samples': [True, False, False, False, True, False, None, False, False, None, True, False]}, ['occ', 'occ', 'clr', 'clr', 'occ', 'occ', 'occ', 'occ', 'clr', 'occ', 'occ', 'occ']), ('control 48', {'period_ms': 250, 'pickup_ms': 750, 'samples': [False, False, True, True]}, ['occ', 'occ', 'occ', 'occ']), ('control 51', {'period_ms': 100, 'pickup_ms': 750, 'samples': [False, None, True, False, False, False, True, False]}, ['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: pick-up exactly at the delay['occ', 'occ', 'clr']['occ', 'clr', 'clr']Failed
regression: receiver failure on a clear section['occ', 'occ', 'occ', 'occ']['occ', 'clr', 'occ', 'occ']Failed
regression: bobbing shunt while occupied['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'clr']Failed
regression: receiver failure mid pick-up['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'clr']Failed
boundary: never clears['occ', 'occ', 'occ']['occ', 'occ', 'occ']Passed
control 1['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed
control 4['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed
control 7['occ', 'occ', 'occ', 'occ', 'occ', 'occ']['occ', 'occ', 'occ', 'occ', 'occ', 'occ']Passed

SHA-256 / 10bdef7e95b02afd1c278deb569dff8dca41033b255709c17a6dcc5d73da8ea0

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

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Verification & scope

Stipulated toy interlocking contract for a bounded teaching model; it makes no claim of conformance to any railway signalling standard and omits real safety cases. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:47:48.733266+00:00.

Case digest / f70b44e21399f64944b37a7cc3a722eb5774a7bc4331addb8ed4010d72d94836