Traffic Signal Timing: clearance_interval
HCM 6th Edition (TRB 2016) traffic signal timing parameters — base saturation flow rates, adjustment factors (lane width fw, heavy vehicles fHV, grade fg, parking fp, bus blockage fbb, area type fa, turning fLT/fRT), LOS thresholds A–F by control delay, startup and clearance lost time, yellow/all-red interval design values, pedestrian WALK and FDW timing (MUTCD 2009), Webster optimal cycle length parameters, and v/c ratio thresholds.
| parameter type | record id | description | notes | unit | value typical (varies) |
|---|---|---|---|---|---|
| clearance_interval | yellow_45mph | Yellow change interval — 45 mph approach | Y = 1.0 + 45*1.47/(2*10) + 0 ≈ 4.3s, typically set to 4.0–4.5 s | s | 4 |
| clearance_interval | yellow_55mph | Yellow change interval — 55 mph approach | Y ≈ 1.0 + 55*1.47/(2*10) ≈ 5.0s | s | 5 |
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