Transportation Engineering
Traffic Signal Timing Calculator
Intersection Parameters
Enter the intersection parameters to calculate optimal signal timing. Based on the Webster method for signal timing.
Phase-Specific Volumes
| Phase | Volume (veh/hour) | Turn Type |
|---|---|---|
| Phase 1 (NB Through) | ||
| Phase 2 (SB Through) | ||
| Phase 3 (EB Through) | ||
| Phase 4 (WB Through) |
Signal Timing Results
Cycle Length
90
seconds
Effective Green Time
67
seconds
Total Lost Time
12
seconds
Optimal Cycle Length
90
seconds
Phase Timing Details
| Phase | Green Time (s) | Yellow Time (s) | All-Red (s) | Total (s) |
|---|
Signal Timing Diagram
Capacity and Performance
Calculation Methodology
This calculator uses the Webster method for traffic signal timing design. Key formulas include:
- Cycle Length (C): C = (1.5 * L + 5) / (1 – Y) where L is total lost time and Y is the sum of critical flow ratios
- Green Time (g): g = (y / Y) * (C – L) where y is the flow ratio for each phase
- Flow Ratio (y): y = V / S where V is volume and S is saturation flow
Additional considerations:
- Yellow time is typically 3-5 seconds based on approach speed
- All-red time is based on intersection clearance needs
- Pedestrian crossing time must be accommodated in the green phase
| Parameter | Typical Value | Description |
|---|---|---|
| Saturation Flow | 1600-2000 veh/h/lane | Maximum rate of flow under ideal conditions |
| Lost Time | 2-4 seconds/phase | Time when no vehicles can move during phase change |
| Cycle Length | 60-120 seconds | Total time for one complete sequence of signal phases |
| Yellow Time | 3-5 seconds | Warning interval following green phase |
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