Traffic Signal Timing Calculator
Calculate optimal cycle length, green time splits, and phase durations for a signalized intersection using Webster's method.
Intersection Parameters
Typical range: 3–5 s. Default is 4 s/phase.
Applied to each phase. Typical: 1,500–1,900 vphg.
Phase Volumes (peak-hour, veh/hr)
Enter intersection parameters and click Calculate Timing to see results.
Phase Timing Breakdown
| Phase | Volume (veh/hr) | Sat. Flow | v/s Ratio | Green (s) | % of Cycle |
|---|
Cycle Allocation
Formula: Co = (1.5L + 5) / (1 − Y), where L = total lost time, Y = sum of critical flow ratios.
Cycle length is rounded to the nearest 5-second increment. Minimum applied cycle: 40 s. Maximum displayed: 180 s.
Results are for preliminary design only. Always verify with pedestrian minimums and local traffic engineering standards.
Summary
Calculate optimal cycle length, green time splits, and phase durations for a signalized intersection using Webster's method.
How it works
- Enter the number of signal phases (2–6) for your intersection.
- Provide the saturation flow rate (vehicles per hour of green) — typically 1,500–1,900 veh/hr.
- Enter the peak-hour volume for each phase in vehicles per hour.
- The calculator computes the flow ratio (v/s) and critical-lane volume for each phase.
- Webster's optimal cycle length formula (Co = (1.5L + 5) / (1 - Y)) is applied.
- Green time is distributed proportionally to each phase's flow ratio.
Use cases
- Preliminary signal timing design for new intersections.
- Re-timing existing signals to reduce delay and improve level of service.
- Transportation engineering coursework and exam preparation.
- Evaluating signal efficiency for traffic impact studies.
- Comparing timing plans for peak vs. off-peak periods.
- Quick feasibility checks before full simulation software runs.