FA-67928 / Traffic signal timing plans / Member archive
Yellow and all-red intervals: the far crosswalk is added when no pedestrians are present · case 03
Yellow and all-red intervals returns a wrong result when the far crosswalk is added when no pedestrians are present.
Case contract
Input {speed_mph, grade_pct (uphill positive), reaction_tenths, decel ft/s^2, width_ft, veh_len_ft, crosswalk_ft, ped}. v = 1.467*speed ft/s; yellow = t + v/(2a + 2*32.2*grade/100), rounded UP to 0.1 s and clamped to [3.0, 6.0]; a non-positive denominator returns 'invalid'. All-red = (W + vehicle length)/v where W includes the far crosswalk when ped is true, rounded UP to 0.1 s and clamped to [1.0, 6.0]. Return tenths.
Why this case matters
Signal timing arithmetic is exact and integer or rational; a wrong rule silently produces unsafe or inefficient timing plans.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| timing oracle 0 | {"red_tenths": 17, "yellow_tenths": 30} | {"red_tenths": 20, "yellow_tenths": 30} | Failed |
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