4-Aspect LED Traffic Lights

A fourth aspect must have a defined job

A 4-aspect traffic light adds one indication to a conventional signal assembly. That extra face might be a protected-turn arrow, a second red or yellow indication, a public-transport symbol, or a countdown display. Because “four aspect” describes the housing count rather than the operating logic, two products with the same exterior shape may serve completely different traffic plans.

The safest way to request this category is to attach a front-view drawing and a phase sequence. Mark every face with its color, symbol and position. Then state whether the fourth indication is switched like a normal lamp output, synchronized from other signal wires, or driven through a controller data interface.

Common four-aspect arrangements

Information required before the housing can be selected

1. Face schedule: list the four colors or symbols from top to bottom or left to right.
2. Operating sequence: show which indications may appear together and the transition intervals.
3. Controller outputs: provide voltage, load method, terminal allocation and any communication protocol used by a countdown display.
4. Physical limits: give the pole arrangement, mounting height, orientation, bracket points and maximum available space.
5. Optical size: specify the diameter of each face; mixed face sizes should be shown on the drawing.
6. Verification documents: identify the standard, language, labels, drawings and test evidence the tender requires.

Protected arrows require system-level review

Adding an arrow is not only a signal-head change. The controller needs a separate phase or signal group, and the intersection conflict matrix must prevent that arrow from running against an incompatible vehicle or pedestrian movement. Detector inputs, minimum green, clearance timing and fallback operation may also change. Use the controller RFQ checklist to describe the whole intersection before requesting cabinet capacity.

Countdown displays require an interface decision

A countdown can follow the energized red, yellow and green circuits, receive a dedicated trigger, or communicate with a compatible controller. The correct method depends on the display design and the timing operation. Adaptive or frequently changing phases need special attention because the remaining time may not be fixed. Our traffic signal countdown guide explains the questions to settle before ordering.

Four-aspect signal FAQ

Is every four-aspect signal red, yellow, green and arrow?

No. That is a common arrangement, but the fourth face may be a countdown, duplicate color or special symbol. The face schedule must be stated explicitly.

Can different face diameters be used in one housing?

Custom housings can sometimes combine sizes, but the overall dimensions, weight, bracket positions and appearance should be approved from a drawing before production.

Can a fourth module be added to an existing three-aspect head?

It depends on the housing construction, mounting strength, wiring capacity and controller outputs. In many projects, replacing the assembly with a purpose-built four-aspect housing produces a cleaner and easier-to-verify installation.

When is a separate signal head better?

A separate arrow or countdown may be preferable when local placement rules, sight lines, maintenance access or pole loading make a tall four-face housing unsuitable.

Compare the standard 3-aspect range, then send the four-face drawing if the project requires an arrow, countdown or custom indication.