FA-67913 / Traffic signal timing plans / Member archive

Yellow and all-red intervals: the grade term omits the factor of two · case 03

Yellow and all-red intervals returns a wrong result when the grade term omits the factor of two.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

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 fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
timing oracle 0	`{"red_tenths": 21, "yellow_tenths": 35}`	`{"red_tenths": 21, "yellow_tenths": 34}`	Failed

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