Introduction
Incorrect output sizing can waste budget or require later replacement. This guide explains how to determine the intersection’s required outputs, assess spare capacity and compare suitable GAOQIAO models against the electrical load and expansion plan.
Counting Outputs by Intersection Type
A 3-leg T-intersection with no turn arrows uses roughly 8-10 outputs: 3 vehicle phases (one per leg) plus pedestrian phases for the two side-road crossings. A 4-leg intersection with protected left turns on two approaches uses 18-22 outputs. A 4-leg intersection with protected lefts on all four approaches plus pedestrian phases and bicycle signals uses 28-32 outputs. A complex intersection with arrows, transit signals and preemption can use 40+ outputs.
The rule of thumb: count every red, yellow and green separately for every signal head, including pedestrian heads and bicycle signals. Arrow heads count as another full phase (3 outputs each).
Spare Capacity Rules
Always leave 15-20% spare capacity for:
- Future turn arrows after a traffic study
- New pedestrian or bicycle phases
- Detector expansion
- Preemption for emergency vehicles
- Replacement of a damaged output channel
If your design uses 30 outputs, specify a 44-output controller, not a 22. If your design uses 18, a 22-output controller is fine. The cost difference between controller sizes is small compared to the cost of replacing an undersized controller later.
Common Pitfalls
Three pitfalls to avoid:
1. Forgetting overlap phases: protected left turns often need an overlap phase (4 outputs) that runs with the opposing through movement. Skipping this in the count leaves the controller one output short on day one.
2. Not counting pedestrian and bicycle separately: a 3-aspect pedestrian head uses 2 outputs (red man, green man), not 1. Count by lamp, not by head.
3. Counting the same head twice: output demand follows the independently controlled indications and the approved wiring, not the number of physical heads. Map each round and arrow indication before counting channels.
Featured Products
Browse GAOQIAO’s 22-output controllers, 56-output controllers, and the controller output guide.
Conclusion
Count independently switched signal outputs and check the load on each circuit; lamp count and phase count are not interchangeable with output count. Reserve capacity according to the approved expansion plan. Compare the 22, 44 and 56-output options against the signal schedule before requesting a quotation.
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Frequently Asked Questions
What is the smallest controller GAOQIAO sells?
The 6-output fixed-time controller for very small sites. Most intersections need at least 22 outputs.
Can I expand a 22-output controller later?
Output expansion depends on the controller architecture, output hardware, conflict monitoring, cabinet wiring and power capacity. Confirm whether the selected system supports an upgrade or requires replacement. Determine spare capacity from the approved future signal and load plan rather than a universal percentage.
What is the largest controller you supply?
A 56-output configuration is listed in the GAOQIAO catalogue. Any additional output capacity requires confirmation of the model, output hardware, monitoring and cabinet wiring; expansion must not be assumed.
Relevant GAOQIAO products
These public GAOQIAO catalogue pages are related to the guide. Open them for the representative description, then confirm the latest drawing and configuration before ordering.
- Traffic signal controllersWired and solar controllers with 6, 22, 44 and 56 output options.
- LED traffic signal heads200mm, 300mm and 400mm signal heads with MUTCD, EN12368, GB14886 compliance.
- Signal polesVertical, signal arm and double-arm poles for any intersection geometry.
- Spare parts and accessoriesSpare LED modules, lenses, visors, surge arrestors and anchor bolts.