Signal Timing (Webster Method)

Optimum cycle length and green splits for an isolated signalised intersection using Webster’s formula. Flows in veh/h or pcu/h.

1. Global inputs

Sum of start-up + clearance lost times for all phases (e.g. 4 s per phase × 4 phases).
Optional bound. Set to 0 to ignore.
Optional bound. Set to 0 to ignore.

Webster optimum cycle: C₀ = (1.5·L + 5) / (1 − Y), where Y = Σ (qᵢ / sᵢ) over critical movements.
Effective green per phase: gᵢ = (yᵢ / Y) · (C₀ − L).

2. Phase data

Enter one row per phase. Use the critical lane (or critical movement) flow for each phase.

# Phase name Flow qᵢ (veh/h) Saturation sᵢ (pcu/h)