Street Lighting Project – Guangdong Mason Technologies Co., Ltd.

Introduction

LED street lighting has rapidly become the global standard for roadway illumination, offering superior energy efficiency, longer lifespan, and better light quality compared to traditional HPS and metal halide systems. For municipalities, contractors, and project planners, understanding the technical fundamentals of LED street lighting is essential to specify the right solution for each application. This guide covers the key technical considerations—from industry standards and photometric performance to optical design, installation, and quality assurance—to help you make informed decisions for your street lighting projects.

1. Industry Standards and Certification Framework

1.1 IES Standards (North America)

The Illuminating Engineering Society (IES) has established the foundational standards for LED lighting measurement and performance:

• IES LM-79 – Approved method for electrical and photometric measurements of solid-state lighting products–. This standard defines the testing environment, procedures, and parameters for measuring total luminous flux, electrical power, efficacy, and chromaticity of LED luminaires–.

• IES LM-80 – Approved method for measuring lumen maintenance of LED light sources–. This standard requires LED packages, modules, and arrays to be tested at multiple case temperatures (typically 55°C, 85°C, and a third temperature) over a minimum of 6,000 hours (recommended 10,000 hours) to measure lumen depreciation–.

• IES TM-21 – Projecting long-term lumen maintenance of LED light sources–. This standard uses LM-80 test data to extrapolate L70 (time to 70% lumen maintenance) and L50 lifetimes.

• IES RP-8 – Recommended Practice for Design and Maintenance of Roadway and Parking Facility Lighting–. This is the comprehensive reference for roadway lighting design, covering illuminance, luminance, uniformity, and glare requirements.

Key Requirement: For street lighting applications, LED light sources should achieve a luminous efficacy of ≥130 lm/W with a CRI ≥70–. LM-80 testing should verify that lumen maintenance reaches ≥90% after 10,000 hours to ensure long-term brightness.

1.2 ANSI C136 Standards (North American Roadway Equipment)

The ANSI C136 series defines the physical and performance requirements for roadway lighting equipment:

IP Rating: LED street light arrays must be protected to a minimum rating of IP65 per ANSI C136.25.

1.3 EN 13201 (European Standard)

Europe’s harmonized road-lighting standard defines lighting classes for motorized traffic (M classes):

M1 is for high-speed highways and major roads; M2 for secondary roads; M3 for local roads with lower traffic volumes.

1.4 Chinese Standards

For projects in China, CJJ45 (Standard for Lighting Design of Urban Road) defines key performance metrics including average road surface luminance, overall uniformity, longitudinal uniformity, average illuminance, illuminance uniformity, glare threshold increment, and surround ratio. GB/T31832-2015 specifies technical requirements for LED urban road lighting applications.

2. Key Performance Parameters

2.1 Correlated Color Temperature (CCT)

CCT defines the color appearance of a white LED, measured in degrees Kelvin:

Selection Considerations:

• 3000K minimizes Rayleigh atmospheric scattering, reduces circadian disruption, and complies with modern environmental regulations

• 4000K is preferred by most State Departments of Transportation for non-residential roadways

• CRI ≥70 is required for street lighting; IESNA recommends CRI of 50 or higher, while DLC requires a minimum CRI of 50 for outdoor roadway luminaires

2.2 Luminous Efficacy and Wattage Selection

Modern LED street lights achieve luminous efficacy of ≥130 lm/W–. Wattage selection depends on pole height, road width, and required illumination level:

Critical Note: Wattage, lumens, and pole height must be considered together. Increasing pole height without adjusting lumen output may leave portions of the roadway underlit.

2.3 Uniformity and Glare

Uniformity is the ratio of minimum illuminance to average illuminance in an area. Recommended uniformity ratios:

• Residential roadways: 6:1

• Commercial roadways: 3:1

Glare is measured by:

• Threshold Increment (TI) : The percentage increase in threshold contrast required to make an object visible in the presence of glare. EN 13201 limits TI to ≤10% for M1/M2 and ≤15% for M3.

• BUG Rating (Backlight, Uplight, Glare): Luminaires should have a U0 rating to minimize light pollution.

To minimize glare, luminaires should be mounted at heights of at least 30 feet (≈9m) and installed to illuminate the ground rather than throw light upward.

3. Optical Distribution and Luminaire Classification

3.1 IES Luminaire Classification System (LCS)

The IES LCS defines luminaire types based on the lateral (transverse) and longitudinal distribution of light on the road surface.

Lateral Light Distribution Types (based on half-maximum candela trace):

Longitudinal Light Distribution (based on maximum candela trace):

For example, a Type III Medium distribution is suitable for roads of medium width with medium pole spacing.

3.2 Pole Spacing Guidelines

A common field guideline for pole spacing is 3 to 5 times the mounting height–:

• Spacing ≈ 6–10 × mounting height is a starting point, but road width, beam distribution, and surrounding structures affect the final decision

• For roads 5–7m wide with 5–7m poles, spacing of 10–25m is typical–

• For 8m mounting height, spacing of approximately 24m is common–

• Pole height should be at least half the road width

4. Installation Best Practices

4.1 Pre-Installation Checklist

Before installation, verify:

• Pole height matches the LED optic specification

• Existing wiring voltage matches the driver rating (120V / 277V / 347V / 480V)

• Road/sidewalk illumination requirements are clearly defined

4.2 Mounting

LED street lights are typically installed using:

• Horizontal arms

• Vertical pole-top mounts

• Adjustable slip fitters

Critical considerations:

• The fixture should sit level or slightly down-tilted – upward tilt causes glare

• Reusing old arms from sodium lamps may not work—LED optics are more focused

• For double-arm installations, luminaires shall be connected through the arms at the top of the pole

4.3 Wiring

• Power off at the breaker before any connection

• Confirm actual line voltage, not assumed voltage

• Proper grounding (not improvised)

• Secure driver connections, especially with photocells

• LED drivers don’t behave like old ballasts—wrong voltage causes failure

Wiring best practices: Use a strain-relief fitting and add a drip loop to minimize water intrusion.

4.4 Post-Installation Aiming

After installation:

1. Turn on the LED street light at night

2. Walk the area and check from actual pedestrian/driver viewpoints

3. If light spills into windows or hits eye level, adjust immediately

“LED street lights are honest. They show mistakes clearly.”

5. Thermal Management

Thermal management is critical for LED longevity. LED junction temperature increases of 10°C can halve the lifespan. Key considerations:

• Heat sink design: Die-cast aluminum heat sinks with optimized fin geometry

• Thermal simulation: Finite Element Method (FEM) analysis is used to predict junction temperatures

• Testing: Real-world aging tests under various ambient temperatures verify thermal performance

Typical design targets:

• Heat sink temperature stability ≤45°C at 25°C ambient

• Junction temperature below 85°C warranty threshold

6. Quality Assurance and Testing

6.1 Laboratory Testing Capabilities

A qualified LED street light manufacturer should offer comprehensive testing, including:

• Photometric testing (IES LM-79 compliant) – total luminous flux, efficacy, intensity distribution

• Lumen maintenance testing (IES LM-80 compliant) – long-term lumen depreciation

• Environmental reliability – temperature cycling, humidity, salt spray

• Ingress Protection (IP) – IP65 minimum for street lighting

• Surge protection – per ANSI C136.2 requirements

• Vibration testing – per ANSI C136.31

6.2 Key Certifications for Market Access

DLC (DesignLights Consortium) certification is particularly important for utility rebate programs in North America and requires minimum CRI of 50 for outdoor roadway luminaires.

Summary Checklist for LED Street Lighting Projects

This guide is intended as a technical reference for specifiers, contractors, and procurement professionals. For project-specific recommendations, consult with your LED lighting manufacturer or a qualified lighting designer.