Traffic Signal Timing: saturation_flow
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) |
|---|---|---|---|---|---|---|---|
| saturation_flow | base_sfr | Base saturation flow rate (ideal conditions) | Ideal conditions: 12-ft lane, level grade, no parking, no HV, no turns, no pedestrians, no buses; HCM 6th uses 1900 as standard | pc/h/ln | 1,950 | 1,800 | 1,900 |
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