Traffic Light Size Chart: 200mm vs 300mm vs 400mm (8 vs 12 vs 16 Inch)
The diameter of a traffic signal head is chosen by the road class, viewing distance and the type of approach. Compare 200mm (8 inch), 300mm (12 inch) and 400mm (16 inch) LED traffic lights before you commit to a specification.
Size comparison table
| Diameter | Inch equivalent | Typical road class | Visibility distance | Driver decision point | Power per lamp |
|---|---|---|---|---|---|
| 100 mm | 4 inch | Pedestrian indoor, bike path | <50 m | Optional | 3-6 W |
| 200 mm | 8 inch | Side-road, parking, low-speed urban | 50-100 m | <60 m | 6-10 W |
| 300 mm | 12 inch | Urban arterial, school zone, intersection | 100-200 m | 60-120 m | 8-15 W |
| 400 mm | 16 inch | Highway, high-speed arterial, fog-prone | 200-300 m+ | 120-200 m | 12-20 W |
1. Why signal head diameter matters
A signal head that is too small is missed at distance. A signal head that is too large is heavy, expensive and hard to mount. The correct diameter matches the legibility distance to the road speed and the approach geometry.
Three factors drive the choice: approach speed (lower speed tolerates smaller diameter), viewing distance from the driver decision point, and required visibility under ambient light, fog or backlight. National standards often mandate a minimum diameter by road class. EN12368 requires 200mm minimum for vehicle signals on most roads, with 300mm required on roads above a design speed threshold; MUTCD references 200mm and 300mm as the standard sizes, with 300mm required on higher-speed approaches. When the project crosses regions, the larger diameter usually wins.
2. 200mm / 8 inch: pedestrian and low-speed use
The 200mm diameter (8 inch) is the typical choice for pedestrian crossings, side-road approaches, parking entrances and low-speed urban streets. It is also the most common diameter for bicycle signals. Visibility is comfortable up to about 60-80 m, which matches design speeds of 30-50 km/h.
Choose 200mm when the road class is local or residential, the approach speed is below 50 km/h, the signal head is for pedestrian or bicycle use, or the authority prefers a smaller, lighter head on existing poles. The 200mm head is also used on signal arm poles where the additional reach of the arm compensates for the smaller face. Watch for backplate and visor compatibility, since not all 200mm housings accept the same accessories as 300mm.
3. 300mm / 12 inch: standard urban intersections
The 300mm diameter (12 inch) is the workhorse of urban traffic signalling. Visibility ranges from 100-200 m, which covers most urban arterials and signalised intersections at design speeds of 50-70 km/h. Most authorities default to 300mm unless the road class or speed requires more.
Choose 300mm when the road is an urban arterial or collector, the approach speed is 50-70 km/h, the intersection is signalised with vehicle and pedestrian phases, or the project mixes with an existing 300mm neighbourhood for visual consistency. The 300mm head is also the most common diameter for arrow, bicycle and pedestrian signals. Confirm the housing accepts the right indication lens and the right mounting hardware for your pole.
4. 400mm / 16 inch: high-speed and long viewing distance
The 400mm diameter (16 inch) is required on high-speed approaches, highways, motorway on-ramps and intersections with long viewing distances. Visibility exceeds 200 m, which gives drivers more time to detect the signal and react.
Choose 400mm when the approach speed is above 70 km/h, the viewing distance from the decision point exceeds 150 m, the site is fog-prone or has high ambient backlight, or the authority mandates 400mm for the road class. The 400mm head is heavier (typically 15-25 kg) and uses more power per lamp. Confirm the pole, arm and mounting hardware are rated for the higher load, and verify that the cabinet power supply can deliver the additional current.
5. Mixing diameters in one intersection
It is acceptable to mix 200mm and 300mm heads at the same intersection, provided the larger diameter is used for the higher-speed approach. For example, a minor side-road approach can use 200mm heads while the major arterial uses 300mm. Mixing 200mm with 400mm on the same approach is uncommon and usually discouraged for visual consistency.
Common combinations: major arterial 300mm plus side-road 200mm (acceptable); major arterial 400mm plus side-road 300mm (acceptable); vehicle 300mm plus pedestrian 200mm (standard); vehicle 400mm plus pedestrian 300mm (high-visibility pedestrian). For new intersections, choose one diameter per approach and stick to it. The visual rhythm helps drivers recognise the signal faster.
6. How to choose: speed, distance, road type
Use this decision flow. What is the design speed on the approach? Below 50 km/h uses 200mm; 50-70 km/h uses 300mm; above 70 km/h uses 300mm or 400mm depending on viewing distance. What is the visibility distance from the driver decision point? Below 80 m uses 200mm; 80-150 m uses 300mm; above 150 m uses 400mm. What is the road class? Local or residential uses 200mm; collector or minor arterial uses 300mm; major arterial or highway uses 300mm or 400mm. Are there national or local standards to follow? Check EN12368, MUTCD, GB14886, AS/NZS for minimum diameter rules. If two rules disagree (for example speed says 300mm but the road class says 400mm), follow the stricter rule and confirm with the local authority.
7. Other sizes GAOQIAO supplies
GAOQIAO also supplies 100mm (4 inch) signal heads for indoor pedestrian crossings, parking guidance and bicycle paths. These are not road-rated but are useful for tunnels, garages and covered walkways where space is limited.
Frequently asked questions
What is the most common traffic light size?
300mm (12 inch) is the most common diameter for vehicle signals on urban roads. 200mm (8 inch) is the standard for pedestrian and bicycle signals, and 400mm (16 inch) is reserved for highways and high-speed approaches.
Can I use 200mm heads on a main road?
In most cases, no. Most national standards require 300mm or larger for vehicle approaches above 50 km/h. 200mm is allowed only on local, residential or low-speed roads, and for pedestrian or bicycle signals everywhere.
What size do I need for a 60 km/h intersection?
60 km/h is at the upper limit for 300mm. If the visibility distance from the driver decision point exceeds 100 m, choose 400mm for clarity. For shorter viewing distances on a 60 km/h road, 300mm is acceptable.
Are 400mm heads worth the extra cost?
For high-speed approaches above 70 km/h, long viewing distances over 150 m, fog-prone sites or motorway on-ramps, 400mm is required and the cost is justified by safety. For a standard urban intersection, 300mm is sufficient and saves money on the head, mounting hardware and power.
Can I mix 200mm and 300mm heads?
Yes, but with care. Mixing is acceptable when the larger diameter is used for the higher-speed approach. Mixing the same approach with different diameters is generally discouraged for visual consistency.
How big are traffic lights in real life?
The standard road-rated diameter is 300mm (about 12 inches). For comparison, a 300mm head is roughly the size of a basketball hoop opening. 400mm heads are larger and more visible from a distance, but require stronger poles and arm hardware.
Does the diameter affect power consumption?
Yes. A 400mm head typically uses 12-20 W per lamp; a 300mm head uses 8-15 W; a 200mm head uses 6-10 W. For a 12-lamp intersection, switching from 400mm to 300mm can save 30-60 W total, which adds up across the network.
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.
- 200mm (8 inch) LED traffic lightsCompact heads for pedestrian, bicycle and low-speed urban applications.
- 300mm (12 inch) LED traffic lightsStandard heads for urban arterials and signalised intersections.
- 400mm (16 inch) LED traffic lightsLarge heads for highways, motorway on-ramps and fog-prone sites.
- Full LED traffic signal head collection100mm, 200mm, 300mm and 400mm heads with matched accessories.