Traffic Signal Timing: cycle_length
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 max (varies) | value min (varies) | value typical (varies) |
|---|---|---|---|---|---|---|---|
| cycle_length | max_cycle | Maximum recommended cycle length | Cycles >120 s yield diminishing returns; FHWA recommends ≤120 s for actuated; 150 s practical maximum for pretimed | s | 150 | 120 | 120 |
| cycle_length | min_cycle | Minimum cycle length (typical) | Practical minimum 40 s for 2-phase; 60 s for 4-phase; shorter cycles reduce delay at low volumes | s | 60 | 40 | 60 |
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