FA-67940 / Traffic signal timing plans / Member archive

Pedestrian walk and clearance timing: the flashing dont walk interval is truncated · case 05

Pedestrian walk and clearance timing returns a wrong result when the flashing dont walk interval is truncated.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input {crossing_ft, walk_speed_tenths (ft/s*10), min_walk, yellow_tenths, red_tenths, min_green, ped_call, split}. FDW = ceil(crossing*10/speed). Walk starts at min_walk and is extended so that walk + FDW >= ceil((crossing + 6)/3.0) (pushbutton-to-far-curb check at 3.0 ft/s). FDW may overlap yellow and all-red, so with a ped call the vehicle green is max(min_green, ceil(walk + FDW - (yellow+red))). Without a call green = min_green. fits is green + yellow + red <= split. Return {walk, fdw, green, fits}.

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	`{"fdw": 18, "fits": true, "green": 19, "walk": 6}`	`{"fdw": 19, "fits": true, "green": 19, "walk": 5}`	Failed

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