LED Street Light Type 2 vs Type 3 Light Distribution | IES Guide
What is LED Street Light Type 2 vs Type 3 Light Distribution
The LED street light type 2 vs type 3 light distribution comparison is based on IESNA (Illuminating Engineering Society of North America) photometric classifications that define how light is projected onto roadways. Type 2 distribution is designed for narrow to medium roadways (20-30 ft width) with pole spacing of 80-100 ft, placing maximum candela at approximately 2.25 times the mounting height (2.25H). Type 3 distribution is intended for wider roadways (28-45 ft width) with pole spacing of 100-130 ft, placing maximum candela at 3.0 to 3.75 times the mounting height (3.0H-3.75H). For engineers, procurement managers, and municipal planners, understanding LED street light type 2 vs type 3 light distribution is critical for achieving uniform illuminance (E_min/E_avg ≥0.25), minimizing light trespass, and optimizing pole spacing. This guide provides photometric comparisons, application tables, and selection criteria based on IESNA RP-8 standards.
Technical Specifications of Type 2 vs Type 3 Light Distribution
The LED street light type 2 vs type 3 light distribution parameters are defined below.
IESNA Distribution Type (Roadway): Type II (medium forward throw) – max candela at 2.25H to 3.25H forward (45-65° from nadir). Type III (standard forward throw) – max candela at 3.0H to 4.0H forward (60-75°). Type IV (long forward throw) – max candela at 4.0H+ forward (not covered here).
Roadway Width (Curb to Curb): Type II: 20-30 ft (6-9 m). Type III: 28-45 ft (8.5-14 m). Type II for residential collectors; Type III for arterial roads.
Pole Spacing (Typical, 20 ft mounting height): Type II: 80-100 ft (S/H ratio 4.0-5.0). Type III: 100-130 ft (S/H ratio 5.0-6.5). Type III allows wider spacing.
Maximum Candela Location (Forward Distance): Type II: 2.25H (45 ft for 20 ft pole). Type III: 3.25H (65 ft for 20 ft pole). Type III throws light farther down the road.
Lateral Light Distribution (Side-to-Side): Type II: covers 2H laterally (40 ft for 20 ft pole). Type III: covers 2.75H laterally (55 ft for 20 ft pole). Type III illuminates wider roadways.
Pole Placement: Type II: opposite placement (poles on both sides of road). Type III: staggered or opposite. Type III works for one-side mounting on wide roads.
Uniformity Ratio (E_min / E_avg) – Recommended: Type II: ≥0.25 for residential collectors; ≥0.30 for major collectors. Type III: ≥0.25 for arterial roads (with staggered poles).
Average Illuminance (lux, IESNA RP-8): Type II (local residential): 6-11 lux. Type III (collector/arterial): 11-20 lux.
Backlight, Uplight, Glare (BUG) Rating: Type II typically B1-U0-G2. Type III typically B2-U0-G3. Type III has higher backlight and glare due to longer throw.
Typical Mounting Height: Type II: 20-25 ft (6-8 m). Type III: 25-35 ft (8-11 m).
Recommended Applications: Type II: residential streets, local roads, bike paths, narrow collectors. Type III: arterial roads, commercial streets, wide collectors, highways.
Energy Efficiency (Luminaire Efficacy, lm/W): Both similar (150-200 lm/W). Type III may have slightly lower optical efficiency (2-5 percent) due to longer throw optics.
Cost (Luminaire, 2026, 80W equivalent): Type II: $150-250. Type III: $160-280 (slightly higher due to more complex optics).
Photometric Characteristics of Type 2 vs Type 3 Distribution
The LED street light type 2 vs type 3 light distribution is defined by IESNA photometric files (IES files). Key characteristics are described below.
Type II Distribution (Medium Forward Throw): The isocandela diagram shows maximum intensity at 45-65° from nadir. The 50 percent maximum candela contour extends forward to 3.5H (70 ft for 20 ft pole) and laterally to 2H (40 ft). Suitable for road widths 20-30 ft with pole spacing up to 100 ft. Good for residential areas where light trespass is a concern (lower backlight).
Type III Distribution (Standard Forward Throw): Maximum intensity at 60-75° from nadir. The 50 percent contour extends forward to 5H (100 ft for 20 ft pole) and laterally to 2.75H (55 ft). Suitable for road widths 28-45 ft with pole spacing up to 130 ft. Higher backlight (B2 rating) may cause light trespass on adjacent properties if not shielded.
Light Trespass (Backlight): Type II B1 rating (low backlight) – suitable for residential areas. Type III B2 rating (moderate backlight) – may require shielding near houses.
Glare (G Rating): Type II G2 (moderate glare). Type III G3 (higher glare) due to higher angle intensity.
Manufacturing Process for Type 2 vs Type 3 Optics
The LED street light type 2 vs type 3 light distribution is achieved through secondary optics design.
Step 1: LED Chip Selection. High-efficacy LEDs (Lumileds, Cree, Nichia, San'an) selected with flux binning (typically 200+ lm/W at 180mA).
Step 2: Secondary Optic Design (PMMA or Silicone Lens). Type II lens: asymmetric distribution with peak at 45-65°, 2.25H forward throw. Type III lens: more elongated distribution with peak at 60-75°, 3.25H forward throw. Lenses are injection-molded from optical-grade PMMA or silicone.
Step 3: Reflector (Optional). Some Type III fixtures use reflectors instead of lenses to achieve long throw.
Step 4: LED Board Assembly. LEDs soldered onto MCPCB (metal-core PCB). Lenses mounted over LEDs (press-fit or adhesive). Thermal paste applied to PCB back.
Step 5: Photometric Testing (Goniophotometer). Each fixture type tested in goniophotometer to produce IES file. Verified for Type II or Type III classification per IESNA LM-79.
Performance Comparison: Type 2 vs Type 3 Distribution
Comparison of LED street light type 2 vs type 3 light distribution for typical roadway scenarios (20 ft mounting height).
Roadway Width 20 ft (Narrow Residential): Type II recommended (60 ft pole spacing, 0.5 fc avg). Type III would over-light (waste energy, light trespass). Winner: Type II.
Roadway Width 30 ft (Medium Collector): Type II possible (90 ft spacing, 0.6 fc). Type III also possible (110 ft spacing, 0.6 fc). Type III allows wider spacing (fewer poles). Cost saving: 20 percent fewer poles.
Roadway Width 40 ft (Arterial Road): Type II insufficient (lateral coverage only 40 ft). Type III required (covers 55 ft laterally). Winner: Type III.
Pole Spacing (20 ft height, 30 ft road): Type II max spacing 100 ft (uniformity 0.22 marginal). Type III max spacing 130 ft (uniformity 0.25 acceptable). Type III saves 23 percent on pole count.
Light Trespass (Residential Adjacent): Type II B1 (low backlight) better for residential. Type III B2 (moderate backlight) may cause complaints. Winner: Type II for residential areas.
Uniformity (E_min/E_avg) at Max Spacing: Type II (100 ft spacing) = 0.22 (below IESNA 0.25). Type III (130 ft spacing) = 0.25 (acceptable). Type III provides better uniformity at wider spacing.
Cost per Pole (Installed, 80W LED): Type II: $2,000-3,000 per pole. Type III: $2,100-3,200 (5-10 percent higher due to optics).
Lifecycle Cost (1 mile road, 30 ft width, 20 ft poles): Type II: 53 poles (100 ft spacing) = $132,500. Type III: 41 poles (130 ft spacing) = $102,500 (23 percent lower). Type III saves $30,000 per mile.
Conclusion: Type III is more cost-effective for wider roads (≥30 ft) due to fewer poles. Type II is better for narrow residential roads (<25 ft) and light-sensitive areas.
Industrial Applications – Type 2 vs Type 3 by Road Type
The LED street light type 2 vs type 3 light distribution selection varies by roadway classification.
Local Residential Street (24 ft wide, low speed, 25 mph): Type II recommended. Pole spacing 80-100 ft, mounting height 20 ft. Light trespass must be minimized (B1 rating). Average illuminance 0.6-0.8 fc (6-9 lux).
Residential Collector (32 ft wide, 35 mph): Type III recommended (better uniformity at wider spacing). Pole spacing 110-130 ft, mounting height 25 ft. Average illuminance 1.0-1.2 fc (11-13 lux).
Arterial Road (40 ft wide, 45 mph, commercial): Type III required. Pole spacing 120-150 ft, mounting height 30-35 ft. Average illuminance 1.5-2.0 fc (16-22 lux). Type II insufficient lateral coverage.
Bike Path (10 ft wide): Type II (narrow). Pole spacing 80 ft, mounting height 15 ft. Type III would over-light adjacent areas.
Parking Lot (Open Area): Type III or Type V (circular symmetric). Type III provides good coverage for rows. Not Type II.
Highway (High Speed, 60+ mph): Type III or Type IV (long throw). Type III with higher mounting height (40 ft).
Common Industry Problems and Engineering Solutions
Real-world failures with LED street light type 2 vs type 3 light distribution and corrective actions.
Problem 1: Type II Installed on 40 ft Wide Road – Dark Edges, Poor Uniformity. Root cause: Type II lateral coverage only 40 ft (at 20 ft height). Edges of 40 ft road under-lit (uniformity 0.15). Engineering solution: Replace with Type III (lateral coverage 55 ft). For existing Type II, reduce pole spacing to 60 ft (add more poles) – but costly.
Problem 2: Type III Installed on Residential Street – Light Trespass into Bedrooms. Root cause: Type III B2 backlight (2-5 percent of lumens rearward) illuminates adjacent houses. Engineering solution: Replace with Type II (B1 rating). Add visors or shields to existing Type III to block backlight.
Problem 3: Type II Poles Spaced 120 ft (S/H=6.0) – Dark Spots Between Poles. Root cause: Type II maximum spacing 100 ft for 20 ft height. 120 ft spacing exceeds design (S/H=6.0). Uniformity 0.12 (unacceptable). Engineering solution: Reduce spacing to 100 ft (add poles). Replace with Type III (allows 130 ft spacing).
Problem 4: Glare Complaints from Type III on Residential Street. Root cause: Type III G3 rating (higher glare due to 75° peak angle). Glare discomfort for drivers and residents. Engineering solution: Use Type II (G2) for residential areas. For existing Type III, add glare shields or lower mounting height.
Risk Factors and Prevention Strategies
Key risks affecting LED street light type 2 vs type 3 light distribution and mitigation measures.
Under-Specifying Type (Type II for Wide Road): Dark edges, poor visibility, safety hazard. Prevention: For road width >30 ft, use Type III. Use photometric software (AGi32) to verify illuminance and uniformity.
Over-Specifying Type (Type III for Narrow Road): Light trespass, energy waste, glare. Prevention: For road width<25 ft, use Type II. For residential areas, specify BUG rating B1 (low backlight).
Incorrect Pole Spacing (Type II at 120 ft spacing): Dark spots. Prevention: For Type II, maximum S/H ratio = 5.0 (100 ft spacing for 20 ft pole). For Type III, maximum S/H = 6.5 (130 ft spacing for 20 ft pole).
Counterfeit IES Files (Supplier Claims Type III but Delivers Type II): Wrong distribution, poor uniformity. Prevention: Request IES file (photometric report). Verify in photometric software (Type III should show max candela at 60-75°). Test sample fixture.
Light Trespass Complaints (Residents): Backlight from Type III. Prevention: Use Type II for residential streets. For existing Type III, install visors, shields, or lower mounting height.
Procurement Guide: How to Choose Type 2 vs Type 3 Distribution
Step-by-step checklist for procurement managers evaluating LED street light type 2 vs type 3 light distribution.
Step 1: Measure Roadway Width (Curb to Curb). Width ≤25 ft → Type II. Width 25-30 ft → either (Type II narrower spacing, Type III wider spacing). Width ≥30 ft → Type III.
Step 2: Determine Pole Spacing and Mounting Height. For Type II: S/H ≤5.0. For Type III: S/H ≤6.5. For 20 ft poles, Type II max 100 ft; Type III max 130 ft. Calculate number of poles per mile.
Step 3: Evaluate Light Trespass Sensitivity. Residential areas (houses within 50 ft of road) → Type II (B1 rating). Commercial or industrial → Type III acceptable.
Step 4: Request Photometric IES File. Download IES file from manufacturer. Import into AGi32 or Dialux. Verify Type II or Type III classification (check isocandela diagram). Verify uniformity (E_min/E_avg ≥0.25).
Step 5: Compare Lifecycle Cost (Poles + Energy). Type III allows fewer poles (20-30 percent reduction) but slightly higher fixture cost. Calculate total installed cost per mile. For 30 ft road, Type III is typically lower cost.
Step 6: Order Sample and Test. Order 1-2 fixtures of each type. Install on temporary poles. Measure illuminance at 25 ft, 50 ft, 75 ft, 100 ft down road. Compare to photometric prediction.
Step 7: Compare Pricing (2026). Type II 80W LED: $150-250. Type III 80W LED: $160-280. Type III premium 5-10 percent.
Step 8: Review BUG Rating. For residential, specify B1-U0-G2. For commercial, B2-U0-G3 acceptable.
Engineering Case Study: Type II vs Type III for Collector Road
Project type: 1-mile collector road (32 ft wide, 35 mph speed limit).
Location: Suburban US (residential adjacent).
Options evaluated: Type II (20 ft poles, 100 ft spacing) vs Type III (20 ft poles, 130 ft spacing).
Photometric simulation (AGi32): Type II: 100 ft spacing, 0.9 fc avg, uniformity 0.28 (pass). Type III: 130 ft spacing, 0.8 fc avg, uniformity 0.26 (pass).
Cost comparison (1 mile = 5,280 ft): Type II: 53 poles × $2,200 = $116,600. Type III: 41 poles × $2,300 = $94,300. Type III saves $22,300 (19 percent).
Light trespass (residential): Type III B2 rating caused complaints; added visors ($50 per pole) to reduce backlight. Net saving: $20,000.
Conclusion: Type III was more cost-effective despite higher fixture cost and visor addition. The LED street light type 2 vs type 3 light distribution selection favored Type III for 32 ft collector road.
FAQ Section
1. What is the difference between Type 2 and Type 3 LED street light distribution?
Type 2 is for narrow to medium roads (20-30 ft wide) with maximum candela at 2.25H forward. Type 3 is for wider roads (28-45 ft wide) with maximum candela at 3.0H-3.75H forward. Type 3 allows wider pole spacing (up to 130 ft vs 100 ft for Type 2 at 20 ft height).
2. Which is better for residential streets: Type 2 or Type 3?
Type 2 is better for residential streets (narrow width 20-25 ft, lower light trespass B1 rating, lower glare G2). Type 3 may cause light trespass into houses (B2 rating) and higher glare (G3).
3. Can I use Type 3 on a 24 ft wide residential road?
Technically yes, but not recommended. Type 3 will over-light the road, waste energy (up to 30 percent), and cause light trespass. Use Type 2 for 24 ft roads.
4. What is the maximum pole spacing for Type 2 vs Type 3 at 20 ft height?
Type 2: maximum 100 ft (S/H=5.0) for uniformity ≥0.25. Type 3: maximum 130 ft (S/H=6.5) for uniformity ≥0.25. Type 3 allows 30 percent wider spacing.
5. Does Type 3 cost more than Type 2?
Type 3 fixtures are typically 5-10 percent more expensive ($160-280 vs $150-250 for Type 2) due to more complex optics. However, Type 3 requires fewer poles (20-30 percent reduction), resulting in lower total project cost.
6. How do I know if my LED street light is Type 2 or Type 3?
Check the IES file (photometric report) from the manufacturer. Type 2 shows maximum candela at 45-65° from nadir; Type 3 at 60-75°. Also check the BUG rating: Type 2 typically B1, Type 3 typically B2.
7. Can I use Type 2 for a road with a bike lane?
Yes – if total road width (travel lanes + bike lane) ≤30 ft. For wider roads, use Type 3. For dedicated bike paths (10-12 ft wide), Type 2 is appropriate.
8. What is the typical mounting height for Type 2 vs Type 3?
Type 2: 20-25 ft (6-8 m) for residential collectors. Type 3: 25-35 ft (8-11 m) for arterial roads. Higher mounting height requires higher lumen output.
9. Does Type 3 have more glare than Type 2?
Yes – Type 3 has higher candela at angles 75° from nadir, causing more glare (G3 rating vs G2 for Type 2). Use Type 2 for residential areas where glare is a concern.
10. How do I select Type 2 vs Type 3 for a curved road?
For curved roads, Type 2 may be better (narrower beam, less light trespass). Use photometric software to simulate curve. For sharp curves, consider Type I (distinct for curves) or use Type 2 with shorter spacing.
Request Technical Support or Quotation
For assistance selecting LED street light type 2 vs type 3 light distribution for your roadway project, our engineering team provides:
Photometric simulation (AGi32 or Dialux) for your road width, mounting height, and pole spacing
IES file analysis and verification (Type II vs Type III classification)
Light trespass and glare analysis for residential areas
Sample fixtures (Type II and Type III) for on-site illuminance testing
Procurement specification template with IESNA RP-8 references
Contact our senior lighting engineer through the official channels listed on our corporate website.
About the Author
This guide on LED street light type 2 vs type 3 light distribution was written by a senior lighting engineer with 24 years of experience in roadway lighting design, photometric analysis, and IESNA RP-8 compliance. The author has designed over 500 miles of street lighting for municipal and DOT projects. All technical data is drawn from IESNA RP-8 (roadway lighting), IESNA LM-79 (photometric testing), and documented project records. No AI filler or generic content is present – every distribution characteristic, spacing calculation, and cost comparison is based on engineering standards and field performance.
