Highway Lighting Simulation Design — Sunlurio Technical Center

1. Introduction

Highway lighting design is one of the most demanding branches of outdoor illumination engineering. Unlike local roads or urban streets, highways require luminance-based design rather than simple illuminance compliance. The objective is to maintain continuous visual adaptation for high-speed drivers while minimizing glare, flicker, and energy waste. A properly simulated system ensures that each lumen contributes to the safe, efficient guidance of vehicles over long distances.

This document defines the complete design, simulation, and verification process of highway lighting systems based on EN 13201, CIE 115, and IES RP-8. It serves as a technical guideline for EPC engineers, lighting designers, and infrastructure planners developing Sunlurio smart LED highway solutions worldwide.

2. Design Philosophy

Good highway lighting is not about brightness, but balance — between luminance, contrast, and visual comfort. The key design target is not how much light reaches the road, but how the road surface appears to a driver moving at 80–120 km/h. Therefore, simulation must consider the driver’s eye height (1.5 m), viewing direction (1°–2° below horizontal), and the road’s reflection properties (q₀, r-tables).

The design principles are summarized as:

• Luminance-based design: Prioritize uniform luminance (cd/m²) over raw illuminance (lx).
• Visual uniformity: Maintain constant adaptation; avoid flickering contrasts between poles.
• Glare limitation: Control threshold increment (TI) and discomfort glare index (GR).
• Energy optimization: Apply smart dimming and optical efficiency rather than overdesign.
• Simulation validation: Use DIALux EVO or AGi32 to verify every pole position and luminaire tilt.

3. Standards and Reference Framework

All professional highway lighting designs must reference at least one of the following frameworks:

• EN 13201-2: Performance requirements (Europe, Middle East, Asia)
• CIE 115:2020: Lighting of roads for motor and pedestrian traffic
• IES RP-8: American practice (luminance or illuminance approach)
• CIE 140: Road surface and reflection properties

These standards establish the performance indices listed below:

Criterion	Symbol	Definition	Typical Value (ME2–ME3)
Average Luminance	Lavg	Mean road brightness seen by driver	1.0–1.5 cd/m²
Overall Uniformity	U₀	Lmin / Lavg	≥0.4
Longitudinal Uniformity	U₁	Lmin / Lmax along travel axis	≥0.7
Threshold Increment	TI	Percentage glare-induced loss of contrast	≤10–15%
Surround Ratio	SR	Lavg(surround) / Lavg(carriageway)	0.5–0.7
Upward Light Ratio	ULR	Percentage of flux above horizon	≤1%

4. Photometric Theory

4.1 Luminance Equation

At any point P on the pavement, the luminance observed from the driver’s eye position is computed as:

L(P) = Σ [ (I(θi,φi) · cos³(θi)) / (r_i²) ] × ρ(β,φr)

where:

• I(θi,φi): luminous intensity from luminaire i (cd)
• θi: incidence angle from normal
• r_i: distance from luminaire i to point P (m)
• ρ(β,φr): bidirectional reflection coefficient of road surface (depends on CIE r-table)

4.2 Reflection Models

The road surface reflection determines perceived luminance. Asphalt surfaces are classified by CIE road surface types (R1–R4):

Surface Type	Typical Road	q₀ (cd·m⁻²·lx⁻¹)	Description
R1	Dry asphalt	0.07	Specular, dark surface
R2	Average asphalt	0.10	Medium reflection
R3	Concrete	0.12	Light-colored pavement
R4	Light concrete	0.15	Highly reflective

For wet conditions, reduce q₀ by 20–40% depending on surface texture. In DIALux EVO, use the built-in “CIE Road Surface Type” parameter for accurate luminance simulation.

5. Geometric Layout and Pole Arrangement

Geometric variables strongly affect uniformity, glare, and economic performance. The main parameters are:

• Mounting height (H): 8–15 m typical, affects uniformity and glare.
• Spacing (S): distance between poles along carriageway, typically 3.5–4.5×H.
• Overhang (O): 0.5–2.0 m horizontal offset of luminaire from pole axis.
• Setback (B): 1.5–3.0 m from pavement edge to pole base.
• Tilt angle (T): 0°–15°, smaller angles reduce glare and uplight.

5.1 Arrangement Types

Arrangement	Description	Application
Single-sided	Poles on one side of the road	Urban or narrow highway, ≤2 lanes
Opposite	Poles on both sides aligned	Wider roads, 4–6 lanes
Staggered	Poles alternating sides	Most efficient for wide highways
Twin-central	Poles in median with dual outreach	Expressways and dual carriageways

5.2 Spacing-to-Height Ratio Method

The first design estimate often uses the S/H ratio method:

S/H = (K × U₀ × cos³(T)) / (TI_limit)

where K is a constant derived from the luminaire’s optical class and road width. Practical values are:

• ME1–ME2 roads: S/H ≈ 3.5–4.0
• ME3–ME4 roads: S/H ≈ 4.0–4.5
• Collector/feeder roads: S/H up to 5.0

6. Optical System and Luminaire Selection

• Use asymmetric cut-off optics (Type II, III, or IV) to direct light along carriageway.
• Choose luminaires with BUG rating B1-U0-G1 or better to minimize sky glow.
• Recommended CCT: 3000–4000 K for human comfort and contrast visibility.
• CRI ≥70 is acceptable; CRI ≥80 preferred for mixed traffic and toll zones.
• Use optical efficiency ≥90% and luminous efficacy ≥150 lm/W.

7. Simulation Workflow (DIALux EVO / AGi32)

1. Import CAD geometry or create a parametric road section (width, median, verge).
2. Select the correct road surface type (R1–R4) and define observer positions (eye height 1.5 m, distance 60 m).
3. Insert luminaire model with verified IES/LDT file, set mounting geometry and tilt.
4. Define calculation grid for luminance (10 m longitudinal × 0.5 m transverse).
5. Run simulation; analyze Lavg, U₀, U₁, TI, SR, and power density (W/m²).
6. Iterate pole spacing, tilt, and overhang until uniformity and glare targets are achieved.

8. Electrical and Control Design

• Supply voltage: 220–240 VAC single-phase or 380 VAC three-phase.
• Driver: Constant-current DALI-2 / 1–10 V type, PF ≥0.95, THD ≤10%.
• Surge protection: SPD 10–20 kV at each luminaire, compliant with IEC 61000-4-5.
• Control logic: Astro-timer + photocell + traffic-adaptive dimming (LoRa / NB-IoT compatible).
• Cable sizing: ΔV ≤4% (per IEC 60364), Cu cross-section S ≈ (2 × L × I) / (γ × ΔV).

9. Energy Efficiency and Dimming Strategy

Highway lighting operates typically 4200–4500 hours per year. Smart control reduces energy by 40–60% without affecting safety.

P(t) = P₀ × [Ereq(t) / Emax]^n     (n ≈ 1.2–1.4)

Example: 100% output from sunset–22:00, 70% from 22:00–24:00, 50% after midnight (low-traffic period). Power control through DALI-2 scenes or Sunlurio Cloud gateway allows real-time adjustment based on vehicle flow data.

10. Verification and Field Measurement

• Perform measurement per EN 13201-4 using a calibrated luminance meter or HDR camera.
• Observer height: 1.5 m; measurement grid spacing ≤10 m along road centerline.
• Verification tolerance: Lavg ±10%, U₀ ±0.05, TI ±2%, alignment error ≤1°.
• Test both dry and wet conditions; adjust reflection type accordingly.

11. Maintenance and Reliability

• Maintenance factor (MF): 0.75–0.85 based on environment.
• Replace luminaires when output drops below 80% of initial luminous flux or after 50,000 h operation.
• Inspect SPD counters semi-annually; replace if cumulative surge events >500.
• Integrate asset tracking via Sunlurio Cloud for predictive maintenance.

12. Case Study: Six-Lane Expressway Simulation

Design input: Dual carriageway, 12 m total width, R2 surface, 10 m pole height, 35 m spacing, staggered arrangement, Type III optics, 3500 K, 150 W LED.

Simulation results (DIALux EVO):

Parameter	Result	Requirement	Status
Lavg	1.52 cd/m²	≥1.5 cd/m²	Pass
U₀	0.43	≥0.4	Pass
U₁	0.74	≥0.7	Pass
TI	9%	≤10%	Pass
Power density	1.32 W/m²	—	Efficient

Compared to a legacy 250 W HPS system, energy consumption reduced by 58%, and maintenance interval extended from 12 to 36 months.

13. Environmental and Safety Considerations

• ULR ≤1% to minimize sky glow; use full cut-off optics.
• Spill light to roadside property ≤5 lx (vertical plane at 2 m height).
• Ensure pole foundations comply with EN 40 and local wind load codes (e.g., EN 1991-1-4).
• Corrosion protection: hot-dip galvanized steel (ISO 1461) + powder coating for coastal zones.

14. Deliverables and Documentation

• 3D DIALux/AGi32 simulation report (Eh, Lavg, U₀, U₁, TI, SR, power data).
• IES/LDT photometry database with manufacturer verification.
• Single-line wiring diagrams and pole layout drawings.
• Foundation and structural calculation reports.
• Control topology, addressing map, and commissioning test records.

15. Summary

Highway lighting simulation design is the intersection of photometry, geometry, and human factors. Every pole position, every beam angle, and every reflection coefficient must be validated against physics and driver perception. Through advanced simulation with DIALux EVO and AGi32, Sunlurio engineers transform design theory into measurable safety and energy outcomes. The result: a reliable, efficient, and environmentally responsible highway lighting network built for 24/7 performance.

Author Introduction

Written by the Sunlurio Roadway Lighting Division. The team specializes in EN 13201 / IES RP-8 simulation, optical optimization, and smart dimming system integration for expressways, tunnels, and interchanges across Africa, Southeast Asia, and the Middle East.