Traffic Signal Timing: volume_capacity
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 typical (varies) |
|---|---|---|---|---|---|---|
| volume_capacity | vc_near_capacity | v/c ratio — near capacity | 0.85 ≤ v/c ≤ 1.0: approaching instability; high sensitivity to demand variations | dimensionless | 1 | 0.9 |
| volume_capacity | vc_undersaturated | v/c ratio — undersaturated condition | v/c < 0.85: normal operating range; good signal progression | dimensionless | 0.85 | 0.7 |
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