Traffic Signal Visor Types and Functions: Tunnel, Cowl and Directional
Introduction
A traffic signal visor shades the lens from sunlight and prevents sun phantom (the sun making a signal appear illuminated when it is not). The right visor improves visibility and reduces crashes. This guide covers the three common types.
Tunnel Visor
A tunnel visor wraps around the lens like a tunnel, blocking sunlight from any angle except the driver's approach. Tunnel visors provide the best sun-phantom protection and are the default for vehicle signals on straight approaches.
GAOQIAO tunnel visors are made from UV-stable polycarbonate in the same colour as the housing (black, yellow or green) and ship pre-installed on every signal head.
Cowl Visor
A cowl visor is a partial hood that extends from the top of the lens downward. It blocks sun from above but not from the side. Cowl visors are used where the approach angle is mostly from one direction (e.g., a one-way street).
Cowl visors are less effective against sun phantom than tunnel visors but are smaller, lighter and cheaper. GAOQIAO offers cowl visors as an option on all signal heads.
Directional Visor
A directional visor is shaped to limit the visibility of the signal to a specific lane. Used on closely-spaced signals where a signal intended for one lane might be visible to drivers in an adjacent lane. Less common than tunnel or cowl.
Visor Length and Sun Phantom
Visor length (the depth of the hood) is the main lever for sun-phantom protection:
- 100mm visor: minimum, suitable for low-sun-angle regions
- 150mm visor: standard for most regions
- 200mm visor: high-sun-angle regions (low latitude, summer)
- 250mm+ visor: extreme cases, tropical latitudes near the equator
GAOQIAO supplies visors in 100mm, 150mm, 200mm and 250mm depths.
Featured Products
GAOQIAO supplies signal heads with pre-installed tunnel visors and optional cowl or directional visors. See the traffic signal IP ratings guide for related ingress protection.
Conclusion
Tunnel visors are the default and the best sun-phantom protection. Choose cowl for one-way approaches and directional for closely-spaced lanes. GAOQIAO supplies all three with the depth sized to your latitude. Send us your site location for a visor recommendation.
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Frequently Asked Questions
What is sun phantom?
Sun phantom is when direct sunlight reflects off the LED lens and makes the signal appear illuminated even when the LED is off. A proper visor eliminates this.
Should I use a tunnel or cowl visor?
Tunnel is the default. Use cowl only when the approach is strictly one-way and aesthetics favour a smaller hood.
How long does a visor last?
Polycarbonate visors last 10-15 years in normal sun exposure. GAOQIAO visors are UV-stabilised to 15+ years.
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.