Signal timing plan inputs
Use the responsive form below to test cycle length, green allocation, phase capacity, and delay.
Sample intersection scenario
Use this illustrative dataset to understand how the calculator distributes effective green and estimates delay.
| Phase | Volume (veh/h) | Saturation Flow (veh/hg) | Start-up Lost (s) | Yellow (s) | All-red (s) | Min Green (s) |
|---|---|---|---|---|---|---|
| North-South Through | 420 | 1850 | 2 | 3 | 1 | 12 |
| East-West Through | 390 | 1750 | 2 | 3 | 1 | 12 |
| North-South Left | 310 | 1700 | 2 | 3 | 1 | 10 |
| East-West Left | 280 | 1650 | 2 | 3 | 1 | 10 |
| Example output metric | Illustrative value |
|---|---|
| Cycle mode | Auto cycle using Webster method |
| Peak hour factor | 0.92 |
| Estimated cycle length | 180.00 s |
| Total lost time | 24.00 s |
| Effective green pool | 156.00 s |
| Average delay | About 70 s/veh |
| Interpretation | Heavy demand suggests long cycle and close-to-capacity operation. |
Timing model and equations
vadj = v / PHFDemand is increased when the peak hour factor is below 1.00.
yi = vadj,i / siThis compares demand with available saturation flow for each phase.
L = Σ(start-up lost + yellow + all-red)Lost time reduces the cycle portion available for effective green.
C = (1.5L + 5) / (1 - Y), where Y = ΣyiThe calculator caps this value at the maximum cycle you set.
G = C - LThe remaining cycle time is distributed among active phases.
gi = min green + remaining green × (yi / Y)If minimum greens exceed the pool, time is scaled proportionally.
ci = si × (gi / C)Capacity depends on green share and saturation flow.
Xi = vadj,i / cidi = 0.5C(1 - g/C)2 / (1 - Xg/C)This gives an early-planning delay estimate for each phase.
Workflow
- Enter the intersection name and choose auto or manual cycle mode.
- Set the number of active phases from two to four.
- Provide the peak hour factor and maximum auto cycle.
- Fill each active phase with demand volume and saturation flow.
- Enter start-up lost time, yellow time, and all-red time.
- Add the minimum effective green for each phase.
- Press Calculate Timing Plan to display the result above the form.
- Review cycle length, green splits, capacity, v/c ratio, queue, and delay.
- Use the CSV and PDF buttons to export the plan summary and phase table.
FAQs
1) What does this calculator help me decide?
It helps estimate cycle length, green splits, lost time, capacity, v/c ratio, and delay for a multi-phase signalized intersection during early design or review.
2) When should I use auto cycle mode?
Use auto mode when you want a quick planning cycle based on Webster’s method. It is useful for comparing options before field fine-tuning.
3) When is manual cycle mode better?
Choose manual mode when corridor policy, coordinated progression, or agency standards already define the cycle length and you only need split allocation results.
4) Why does the calculator use peak hour factor?
Peak hour factor reflects within-hour demand peaking. Lower values increase adjusted flow, which can raise critical ratios, cycle length, and phase delay.
5) What does a v/c ratio above 1.00 mean?
A value above 1.00 indicates demand exceeds estimated capacity for that phase. This usually signals oversaturation, unstable queues, or the need for timing or geometry changes.
6) Does this replace field timing studies?
No. It is a planning and screening tool. Field observations, detector data, progression needs, pedestrian timings, and agency standards should still guide final implementation.
7) Why are yellow and all-red included as lost time?
These intervals improve safety but reduce the share of the cycle available for effective green. Including them produces more realistic planning-level splits and capacities.
8) Can I use this for left-turn phasing studies?
Yes. You can assign separate protected or permissive-related phases, enter their demand and saturation flow assumptions, and compare timing outcomes across alternatives.