Traffic Signal Timing: adjustment factor
fg plus3 to fp no parking
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 | unit | value max (varies) | value typical (varies) |
|---|---|---|---|---|---|
| adjustment factor | fg plus3 | fg for +3% upgrade (uphill) | dimensionless | 0.985 | 0.985 |
| adjustment factor | fg plus6 | fg for +6% upgrade | dimensionless | 0.97 | 0.97 |
| adjustment factor | fhv 10pct | fHV at 10% heavy vehicles | dimensionless | 0.909 | 0.909 |
| adjustment factor | fhv 15pct | fHV at 15% heavy vehicles | dimensionless | 0.87 | 0.87 |
| adjustment factor | fhv 2pct | fHV at 2% heavy vehicles | dimensionless | 0.98 | 0.98 |
| adjustment factor | fhv 5pct | fHV at 5% heavy vehicles | dimensionless | 0.952 | 0.952 |
| adjustment factor | flt exclusive | Left turn adjustment factor fLT exclusive protected | dimensionless | 0.95 | 0.95 |
| adjustment factor | fp 20maneuvers | fp with parking 20 maneuvers/hr single lane | dimensionless | 0.9 | 0.9 |
| adjustment factor | fp no parking | fp when no parking (reference) | dimensionless | 1 | 1 |
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