Type III vs. Type V Distribution in Commercial Parking Lot Lighting
Light distribution type determines where lumens are delivered across a parking lot surface. Even with the correct mounting height and lumen package, selecting the wrong distribution pattern can result in uneven coverage, excessive glare, or wasted light outside the target area.
Two of the most commonly specified outdoor distributions for parking lots are Type III and Type V. While both are used for area lighting, they serve very different layout and pole placement strategies.
What Light Distribution Means in Parking Lot Design
Light distribution describes how lumens exit the fixture and spread across the ground plane. In parking lot applications, this determines how evenly light levels are maintained between poles, drive lanes, and pedestrian areas.
- Distribution affects uniformity ratios
- It controls spill light beyond property boundaries
- It influences pole spacing and pole quantity
Distribution type must be evaluated alongside site geometry, pole placement, and mounting height.
Type III Distribution: Forward Throw Explained
Type III distribution is commonly referred to as a forward throw pattern. Light is projected outward in an elongated shape, extending away from the pole.
Where Type III Performs Best
- Perimeter-mounted poles along parking lot edges
- Poles located near building lines or property boundaries
- Layouts requiring light to be pushed forward into the lot
Key Photometric Characteristics
- Asymmetrical distribution pattern
- Reduced backlight behind the pole
- Forward projection that supports edge-to-interior coverage
Type III is commonly used when poles are installed along one side or along the perimeter rather than evenly spaced throughout the site.
Type V Distribution: Circular Coverage Explained
Type V distribution produces a symmetrical, circular light pattern centered beneath the fixture. Light is distributed evenly in all directions.
Where Type V Performs Best
- Interior parking lot poles
- Large open areas with evenly spaced poles
- Layouts prioritizing uniform light levels around each pole
Key Photometric Characteristics
- Symmetrical, 360-degree coverage
- Balanced illumination around the pole base
- Minimal directional bias (not intended to “push” light forward)
Type V is typically selected when poles are positioned within the lot (grid layouts) rather than at boundaries.
Type III vs. Type V: Quick Comparison
| Category | Type III (Forward Throw) | Type V (Circular) |
|---|---|---|
| Distribution Shape | Asymmetrical; elongated pattern that projects outward | Symmetrical; circular pattern around the pole |
| Best Pole Location | Perimeter / edge poles | Interior / grid poles |
| Primary Design Advantage | Pushes light into the lot from edges | Uniform coverage around each pole |
| Common Risk if Misapplied | Hot spots and uneven overlap if used in a tight interior grid | Spill and perimeter trespass if used near edges |
| Typical Use Case | Parking lot perimeters, boundary-adjacent placement | Large open lots, evenly spaced pole fields |
Pole Placement and Layout Strategies
Pole location is the primary factor when choosing between Type III and Type V distributions.
- Perimeter poles typically pair with Type III optics to throw light inward
- Interior poles typically pair with Type V optics for balanced coverage
- Some lots require a mix of distributions based on edges vs. interior zones
Using the wrong distribution for pole placement often forces compensating moves (higher wattage, tighter spacing, excessive tilt) that reduce uniformity and increase glare.
Parking Lot Layout Examples and Distribution Selection
| Layout Condition | Typical Pole Placement | Preferred Distribution | Why It Fits |
|---|---|---|---|
| Perimeter-only layout | Poles around edges; few or none in the interior | Type III | Projects light forward into the lot and limits backlight beyond the boundary |
| Interior grid layout | Poles evenly spaced across the parking field | Type V | Circular coverage supports uniform overlap between poles |
| Mixed layout (edges + interior) | Perimeter poles plus interior poles at higher density zones | Type III (edges) + Type V (interior) | Different zones need different coverage geometry to maintain uniformity and control spill |
| Lot adjacent to residences or roadway | Perimeter poles near sensitive boundaries | Type III (with perimeter control) | Forward throw helps limit backlight while maintaining interior illumination |
Mounting Height and Spacing Considerations
Mounting height affects how each distribution performs on the ground plane.
- Higher mounting heights can support wider spacing, but only when the distribution matches the pole layout
- Lower mounting heights typically require tighter spacing and more careful glare control
- Over-spacing with the wrong distribution increases low-light gaps between poles
Distribution selection should be validated through photometric analysis rather than assumed from fixture wattage or lumen output.
Glare, Light Trespass, and Perimeter Control
Distribution type influences both perceived glare and spill beyond property lines.
- Type III reduces backlight toward buildings, streets, and adjacent properties when used on perimeters
- Type V can create perimeter spill when used near edges because it distributes light in all directions
- Glare risk increases when aiming or tilt is used to compensate for poor pole placement
Where boundary control matters, distribution choice should be evaluated with shielding options and site constraints.
Common Distribution Selection Mistakes
- Using Type V on perimeter poles and then increasing tilt or wattage to reach the interior
- Using Type III in an interior grid and creating inconsistent overlap between poles
- Assuming lumen output can compensate for incorrect distribution geometry
- Ignoring boundary conditions and adjacent uses (residential, roadway, storefront glazing)
Parking lot lighting problems are often the result of distribution and layout mismatch rather than insufficient lumen output.
Related Outdoor Lighting Categories
Type III and Type V distributions solve different placement problems. When the optic matches the pole layout, uniformity improves, glare is easier to control, and fewer compensating adjustments are needed.
Brandon Waldrop
As the lead technical specialist for our commercial lighting technical operations, Brandon Waldrop brings over 20 years of industry experience in product specification, outside sales, and industrial lighting applications.
His career began in physical lighting showrooms, where he focused on hands-on product performance and technical support. He later transitioned into commercial outside sales, working directly with architects, electrical contractors, and facility managers to translate complex lighting requirements into energy-efficient, code-compliant solutions.
Today, Brandon applies that industry experience to architect high-performance digital catalogs and technical content systems, helping commercial partners streamline the specification process and deploy lighting solutions with total technical confidence.
