Why Output Capacity Matters
Output capacity describes the available switched signal circuits, subject to the equipment design and electrical ratings. Detector inputs, communication channels and programmable phases are separate capacities that must also be checked when selecting a controller.
This guide shows when to choose 22, 44, or 56 output controllers and the future-proofing rules that keep your investment flexible.
The Three Standard Capacities
| Capacity | Typical Use | Max Phases | Detector Inputs | Preemption Channels |
|---|---|---|---|---|
| 22 output | Small intersection, single corridor | 4-6 | 8-16 | 2-4 |
| 44 output | Mid-size arterial, 4-8 phases | 8-12 | 16-32 | 4-8 |
| 56 output | Complex intersection, multiple corridors | 12-16 | 24-48 | 8-12 |
Most intersections fit within 22 outputs. Choose 44 or 56 when the intersection has protected left turns, pedestrian phases, transit priority, or future expansion planned.
When 22 Output Is Enough
A 22-output controller handles:
- 4-approach intersection with ball signals
- Up to 2 protected left turns
- 4-8 pedestrian push buttons
- 1-2 preemption channels
- 8-16 vehicle detectors
Potential applications for 22-output controllers, subject to review of the phase plan and electrical loads, include:
- T-intersections with permissive turns only
- 4-leg intersections with no protected lefts
- Rural crossroads with flashing beacon mode
- New developments where traffic patterns are still developing
When 44 Output Is the Right Choice
A 44-output controller covers:
- 4-leg intersection with all 4 protected left turns
- 8-12 phases including overlaps
- Pedestrian phases on all 4 corners
- Transit signal priority (TSP)
- Emergency vehicle preemption on multiple approaches
- Adaptive control integration
Potential applications for 44-output controllers, subject to review of the phase plan and electrical loads, include:
- Urban arterials with frequent transit
- Intersections near hospitals or fire stations
- Mid-size cities building toward smart infrastructure
- Corridors that may add bike signals later
When 56 Output Becomes Essential
A 56-output controller is the right choice for:
- Intersections with bike signals AND transit AND ped AND vehicles
- Complex corridors with multiple preemption agencies
- Intersections integrated with city-wide adaptive systems
- Major junctions with railway preemption
- Borders or customs crossings with variable lane control
Potential applications for 56-output controllers, subject to review of the phase plan and electrical loads, include:
- 5-way or larger intersections
- Border crossings
- Airport access roads
- Port terminal entrances
Future-Proofing Rule
Always choose one size larger than current minimum needs. Here’s why:
If the confirmed requirement is 28 outputs, a 22-output controller is insufficient; assess a 44-output model against the required electrical loads, interfaces and expansion margin. Compare project quotations for the larger initial configuration and any later replacement, programming and commissioning. Upgrade percentages and future costs must be calculated for the actual project.
Add 20-30% spare capacity for:
- Future protected left turn (if permissive today)
- Future transit signal priority
- Future bike signal integration
- Future smart city sensor integration
Capacity Calculation Worksheet
For your intersection, count:
1. Vehicle signals: (number of approaches) × 3 + (protected lefts) × 2
2. Pedestrian signals: (number of crosswalks) × 2
3. Bike signals: (number of approaches) × 3
4. Preemption: (number of agencies) × 1
5. Spare: +20% of total
Example calculation: 4-leg intersection with all 4 protected lefts:
- Vehicle: 4 × 3 = 12
- Left arrows: 4 × 2 = 8
- Pedestrian: 4 × 2 = 8
- Total: 28
- +20% spare: 5.6
- Grand total: 34 → Choose 44 output
When 22 Is Too Small (Common Mistakes)
Three signs you’ve outgrown a 22-output controller:
1. Using overlap phases as workarounds
2. Multiple detection zones sharing one channel
3. Preemption consuming all spare capacity
If any of these apply, upgrading to 44 is more cost-effective than living with the limitation.
Conclusion
Choose 22 output for simple intersections, 44 for most urban signals, 56 for complex multi-modal junctions. Always add 20-30% spare capacity for future expansion. The cost premium for one size up is far less than the cost of upgrading later.
Send your intersection layout to discuss the appropriate output capacity. Programming interfaces, documentation and sizing assistance must be confirmed for the selected model and quotation.
Get a Quote
Send us your intersection drawing and current controller model. We will return a recommended output capacity and a matching quotation.
Email: sky-sale@njgq.net
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Tel: +86-25-84471080
Frequently Asked Questions
Can I upgrade from 22 to 44 outputs later?
The controller hardware is fixed-size. Upgrading means replacing the controller, reprogramming, and re-commissioning. Plan for future growth at install time.
How do I know if I need 44 or 56?
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.
Is 56 output controller more expensive than 44?
About 15-20% more for the controller itself, but the cabinet, conflict monitor, and detector cards are similar. The bigger cost is future expansion.
Can I add outputs to a 22-output controller later?
No. Output ports are physically soldered. Choose the right size at the start.
Related GAOQIAO Products
These public GAOQIAO catalogue pages are related to this article.
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- Spare partsLED modules, lenses, visors and accessories.