FA-67161 / Railway interlocking logic / Open access

Signal lamp proving and aspect degradation: double yellow lamp set · case 01

A double yellow is displayed with one of its two lamps dark.

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

ROOT CAUSE

The double yellow aspect only proves one yellow lamp.

VERIFIED REPAIR

Require both yellow lamps for the double yellow aspect.

Unsuccessful approach: Proving only the upper yellow still shows a single yellow as a double yellow.

Case contract

Aspects need lamps: G needs G; YY needs Y1 and Y2; Y needs Y1; R needs R. A lamp is lit if its main or auxiliary filament works. If the requested aspect cannot be lit, show the next more restrictive aspect that can (G, YY, Y, R); if even R cannot be lit the signal is DARK. alarm is raised if the signal is DARK or any lamp used by the shown aspect runs on its auxiliary filament. degraded means shown != requested.

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):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y2'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = shown == 'DARK' or any(not lamps[l]['main'] for l in need[shown])
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 17', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('sampled regression 13', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False}), ('control 21', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 2', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 47', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 65', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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 fixture	Actual	Expected	Outcome
regression: upper yellow dead under double yellow	`{'alarm': False, 'degraded': False, 'shown': 'YY'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Failed
boundary: lower yellow dead under double yellow	`{'alarm': False, 'degraded': True, 'shown': 'Y'}`	`{'alarm': False, 'degraded': True, 'shown': 'Y'}`	Passed
sampled regression 17	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Failed
boundary: second yellow on auxiliary	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	Passed
boundary: green on auxiliary filament	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	Passed
control 1	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 4	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 7	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	Passed

SHA-256 / 42a6f8c8be6f655914f52aa2a1b4f8bf0c2afadfbed4fbf6bcc81928a6144a74

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y1'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = shown == 'DARK' or any(not lamps[l]['main'] for l in need[shown])
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 17', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('sampled regression 13', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False}), ('control 21', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 2', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 47', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 65', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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 fixture	Actual	Expected	Outcome
regression: upper yellow dead under double yellow	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Passed
boundary: lower yellow dead under double yellow	`{'alarm': False, 'degraded': False, 'shown': 'YY'}`	`{'alarm': False, 'degraded': True, 'shown': 'Y'}`	Failed
sampled regression 17	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Passed
boundary: second yellow on auxiliary	`{'alarm': False, 'degraded': False, 'shown': 'YY'}`	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	Failed
boundary: green on auxiliary filament	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	Passed
control 1	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 4	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 7	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	Passed

SHA-256 / 8e5eef88b03451bd6350cd543ea1e8f2a77dd152242076497bacd9fe5bc3453c

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y1', 'Y2'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = shown == 'DARK' or any(not lamps[l]['main'] for l in need[shown])
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 17', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('sampled regression 13', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False}), ('control 21', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 2', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 47', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('sampled regression 65', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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 fixture	Actual	Expected	Outcome
regression: upper yellow dead under double yellow	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Passed
boundary: lower yellow dead under double yellow	`{'alarm': False, 'degraded': True, 'shown': 'Y'}`	`{'alarm': False, 'degraded': True, 'shown': 'Y'}`	Passed
sampled regression 17	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	`{'alarm': False, 'degraded': True, 'shown': 'R'}`	Passed
boundary: second yellow on auxiliary	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	`{'alarm': True, 'degraded': False, 'shown': 'YY'}`	Passed
boundary: green on auxiliary filament	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	`{'alarm': True, 'degraded': False, 'shown': 'G'}`	Passed
control 1	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 4	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	`{'alarm': False, 'degraded': False, 'shown': 'G'}`	Passed
control 7	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	`{'alarm': False, 'degraded': False, 'shown': 'R'}`	Passed

SHA-256 / 1f4ea21d999c6991a38f5ac68111d8678975be310fb3ef59a5cb9909959952ab

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 2026-09-29T14:47:50.333371+00:00.

Case digest / 1d7a374ac2c91fc8259faf165ec874f6537f468d66f4bfb19eb2212883a90215