How to Choose 100mm, 200mm, 300mm or 400mm LED Traffic Signals
Signal diameter is a planning input, not a shortcut for the whole specification. The right size depends on approach speed, viewing distance, lane geometry, mounting height, indication type and the authority鈥檚 standard.
Size comparison at a glance
| Nominal size | Typical planning use | Questions to confirm |
|---|---|---|
| 100 mm | Portable, temporary, compact or special-purpose indications | Is the viewing distance short enough, and is the local standard allowing this size? |
| 200 mm | Urban streets, compact intersections and space-limited installations | Will the face remain visible in sun, rain and motorcycle-heavy traffic? |
| 300 mm | General vehicle approaches and many international project specifications | Confirm section count, optical face, visor and controller outputs. |
| 400 mm | Longer viewing distances, wide approaches and high-visibility projects | Check pole load, wind area, mounting bracket and transport dimensions. |
1. Match size to viewing distance and speed
Drivers need enough time to see, interpret and act on the signal. Higher approach speeds and wider intersections usually require a larger optical face or a higher mounting position. Do not use a diameter table as a substitute for a stopping-sight-distance calculation; the road authority鈥檚 approved drawing takes priority.
2. Match size to the indication
A ball, arrow, pedestrian figure and countdown display do not always have the same optical layout. List the indication for every section, including arrow direction and colour. A three-aspect vehicle head, a two-aspect pedestrian head and a single warning flasher should not be quoted under one generic product name.
- Ball signals: red, yellow and green phases for vehicle movements.
- Arrow signals: protected turn or lane movement; specify left, right, straight or combined arrows.
- Pedestrian/bicycle signals: confirm symbol, aspect count, push-button and audible requirements.
- Countdown combinations: confirm timing source and controller data interface.
3. Consider the housing and mounting environment
Larger signals add weight, wind area and transport volume. Confirm the pole, bracket, backboard, cable entry, visor depth and service access before approving a 400 mm option. For coastal or tropical locations, include UV resistance, sealing, drainage and corrosion protection in the request.
4. Use a project selection sheet
- Country, city and road authority.
- Approach speed, lane width and approximate viewing distance.
- Signal diameter and number of sections.
- Indication per section and optical colour.
- Controller model, voltage and wiring method.
- Mounting arrangement, quantity and delivery destination.
GAOQIAO supplies configurable signal heads from compact applications to large intersection equipment. Review the traffic light range, 300 mm signal examples and send the project drawing for a configuration review.
FAQ
Is 300 mm the best default size?
It is a common project size, but it is not universal. Local standards, viewing distance and mounting constraints decide the final selection.
Can different diameters be mixed at one intersection?
Sometimes, especially for pedestrian or auxiliary indications, but the authority should approve the visual hierarchy and mounting arrangement.
What is more important than diameter?
Clear indication, approved optics, controller compatibility, weather protection and a mechanically safe installation are all equally important.
Not sure which diameter fits your project? Share the road layout, required indications and viewing distance.
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