How to Wire a Traffic Light
Correct wiring is what turns a signal head into a safe, serviceable part of the intersection. Work to the approved drawing, label every conductor and confirm polarity and earthing before power is applied.
Wiring checklist
| Step | Key point | Check |
|---|---|---|
| 1. Safety | Isolate and verify no voltage | Lockout and qualified electrician |
| 2. Voltage | 110V/220V AC or 12/24V DC | Match the signal head rating |
| 3. Terminals | Red, yellow, green + common | Label at both ends |
| 4. Controller | Correct output channels | Conflict and fail-safe state |
| 5. Test | Continuity before power | Each indication in turn |
1. Safety first
Traffic signal wiring is mains electrical work. Isolate the supply, verify with a voltage tester that the circuit is dead, and follow the local electrical code and working-zone rules. Only a qualified electrician should terminate the cabinet and connect the signal heads.
2. Confirm the operating voltage
LED traffic lights are commonly supplied for 110V AC, 220V AC, or low-voltage 12/24V DC operation, sometimes with a wide input range. Connecting a signal head to the wrong voltage will damage the driver or modules, so confirm the rating on the label before wiring.
3. Wire colours and terminal blocks
Signal heads use a common wire plus one switched wire per indication. Red, yellow and green each have their own terminal, with a shared neutral or common. The exact colour code and terminal numbering come from the signal schedule, so keep the drawing at the cabinet and match every conductor to it.
Label every cable at both ends. A clear label is faster to fault-find later and prevents a red indication from being terminated onto the green output during commissioning.
4. Connecting to the controller
Each signal indication maps to a specific controller output channel. For a standard three-aspect head, the red, yellow and green channels connect in order; for an arrow, countdown or pedestrian head, the additional indications use their own outputs. Confirm the conflict monitor is programmed so opposing greens can never energise together.
5. Countdown, pedestrian and push-button wiring
A countdown display may be powered independently or driven by the controller through a trigger, learning or communication interface. Pedestrian push buttons and audible units use low-voltage control circuits that are separate from the signal power. Wire these according to the controller manual and test each input and output in turn.
6. Common mistakes to avoid
The most common wiring faults are reversed polarity, mixed-up common and switched conductors, undersized cable, unsealed cable glands that let water in, and missing earthing or surge protection. Each of these causes either immediate failure or intermittent faults that are expensive to chase later.
7. Testing before power
Before energising, check continuity and insulation resistance, verify earthing, and confirm the terminal schedule against the drawing. Then power the signal in a controlled test and walk through red, yellow, green, arrow, pedestrian and countdown indications one by one, recording the result.
Relevant GAOQIAO products
Open these public catalogue pages for representative configurations, then confirm the latest wiring schedule and voltage before installation.
- Traffic signal controllersFixed-time and coordinated controllers with defined output channels.
- 300 mm (12 inch) LED traffic lightsBall, arrow, pedestrian and countdown configurations.
- Wired traffic signal controllers22-output and 56-output controllers and cabinets.