Traffic Signal Head Lens Types and Beam Patterns Explained
Introduction
A traffic signal head lens does two things: it colours the light and shapes the beam. The wrong lens can make a bright LED look dim at the driver's decision point. This guide covers the common lens types and the beam patterns they produce.
Glass vs Polycarbonate
Glass lenses are the legacy choice. They are scratch-resistant, UV-stable and have a clean optical surface, but they shatter on impact and add weight to the housing. Polycarbonate lenses are the modern default. They are impact-resistant (won't shatter), lighter and cheaper to replace. GAOQIAO supplies both, but polycarbonate is the standard in our 200mm, 300mm and 400mm signal heads.
For high-vandalism sites (urban centres, prisons), polycarbonate is the only sensible choice. For airport or industrial sites where replacement is rare and weight is irrelevant, glass is acceptable.
Beam Patterns
Three beam patterns cover most intersections:
- Symmetric: equal intensity in all directions. Used on mid-block pedestrian crossings and at low-speed approaches.
- Asymmetric toward the driver: intensity biased toward the approaching driver's eye line. The default for vehicle signals on straight approaches.
- High-visibility (HB): a tighter, brighter pattern for fog-prone or high-speed approaches.
EN12368 defines intensity classes 1, 2 and 3, with Class 3 the brightest. GAOQIAO signal heads are tunable to any class.
Lens Diameter and Visibility
Lens diameter (200mm, 300mm, 400mm) is the dominant factor in visibility distance:
- 200mm: pedestrian and side-road signals, visible up to ~80 m.
- 300mm: standard urban vehicle signals, visible up to ~200 m.
- 400mm: highway and high-speed approaches, visible up to ~300 m.
Pick the diameter from the design speed and viewing distance, not just the road class.
Featured Products
GAOQIAO supplies signal heads in 200mm, 300mm and 400mm diameters, all with tunable beam patterns.
Conclusion
Glass vs polycarbonate is usually a clear call: polycarbonate for most sites. Beam pattern and intensity class matter more than lens material. GAOQIAO signal heads ship with beam patterns tuned to the diameter and application. Send us your approach speed and viewing distance for a recommendation.
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Frequently Asked Questions
Are polycarbonate lenses as clear as glass?
Modern optical-grade polycarbonate is within 1-2% of glass in transmittance. For driver visibility this is invisible.
Can I replace a glass lens with a polycarbonate lens?
In the same housing, yes, as long as the lens diameter and gasket match. GAOQIAO supplies both lens types with the same mounting geometry.
What beam pattern do I need for a left turn signal?
Asymmetric toward the turning driver's eye line. GAOQIAO's left turn signal heads use an asymmetric pattern that puts peak intensity along the turning radius.
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.