Buyers Guide to LED Street Lighting

LEDs Make Streets Brighter

Street lights serve a critical function in illuminating walkways, driveways, and roadways to ensure safe navigation for both drivers and pedestrians. Making objects clearly visible allows drivers to identify and avoid potential obstructions or hazards. Research demonstrates that proper street lighting reduces car accidents by approximately 40%, making strategic lighting installation essential for passenger safety.

While brightness matters for street lighting, higher intensity alone isn’t the solution. Excessive brightness creates dangerous shadow spots and blinding glare for drivers. Based on our 17 years of experience in commercial lighting, several key factors determine optimal street lighting performance:

• Lumen output specifications
• Surface reflection values of target areas
• Color rendering capabilities
• S/P ratio and mesopic vision considerations
• Balance between maximum, average, and minimum light levels
• Even light distribution patterns
• Proper fixture cutoff angles
• Mounting pole height optimization: Achieving ideal lighting density requires careful height selection, as light intensity decreases with mounting height

Traditional metal halide street lamps create harsh glare that blinds oncoming traffic. LED technology eliminates this problem through superior optical control and directional light distribution.

Brightness of the Street Lights

The Angle Made by Light Above the Nadir

Nadir represents the downward angle measured from a light fixture’s center point, perpendicular to the ground surface. The Illuminating Engineering Society (IES) uses nadir measurements to classify street lights into four distinct categories based on light distribution patterns:

• Full Cutoff: 0% light output at 90° from Nadir | =10% candlepower at 80° from Nadir
• Cutoff: =2.5% light output at 90° from Nadir | =10% candlepower at 80° from Nadir
• Semi Cutoff: =5% light output at 90° from Nadir | =20% candlepower at 80° from Nadir
• Non-Cutoff: No limitations on light output or candlepower distribution

Full cutoff luminaires direct light downward exclusively, which proves essential for Dark Sky compliance by preventing unnecessary upward light dispersion. This focused approach enables lower wattage requirements since virtually no light gets wasted. Light shields can enhance directionality further, boosting effective brightness while reducing harsh glare production.

Modern LEDs excel at providing inherently directional illumination with superior optics and precise beam control for outdoor applications. While the IES now emphasizes BUG (Backlight, Uplight, Glare) rating systems for comprehensive evaluation, many municipalities still reference traditional cutoff classifications for street lighting specifications.

What Makes the Full Cut-off Lights So Crucial?

Energy conservation and environmental light pollution reduction drive the importance of full cutoff lighting systems. This approach aligns with Dark Sky preservation initiatives that maintain night-friendly skies for astronomical observation while minimizing artificial lighting effects on nocturnal wildlife circadian rhythms.

Reducing fixture contribution to ambient light pollution benefits entire ecosystems. Coastal areas enforce the strictest regulations, though these principles should guide lighting decisions everywhere to protect our natural environment.

Various Luminaries and Their Light Footprint

Different luminaire types serve specific roadway applications according to IES standards. Type 5 fixtures provide 360-degree illumination patterns ideal for roundabouts and four-way intersections, while Type 1 luminaires deliver narrow beam distributions perfect for road medians and walkway lighting.

The Major Hurdle in Calculating the Light Output of Fixtures in Lumens

Standard lumen calculations assume uniform light quality and consistent surface reflection, but reality proves more complex. Surface color significantly affects brightness perception – yellow light striking green objects gets absorbed, making them appear darker than their actual color. However, natural green surfaces like leaves contain multiple pigments including chlorophyll, carotenoids, and xanthophylls that create some yellow light reflection, resulting in grayish appearance.

Low-pressure sodium (LPS) fixtures require higher lumen output because they produce single-spectrum light. LEDs generate full-spectrum illumination that enhances contrast and color differentiation even at lower lumen levels, improving visual perception and driver confidence.

Color Rendering Index (CRI) significantly impacts perceived brightness and object visibility. Higher CRI values make lighting appear brighter with fewer lumens by better stimulating rod cells in human vision. Future LED developments worth considering include:

1. Intelligent Lights

Advanced motion sensor integration allows variable light output based on ambient conditions without compromising visibility. Smart sensors can adjust illumination according to natural light levels while minimizing energy consumption throughout different times of night.

2. Multi-functional Lights

Modern fixtures incorporate data collection capabilities for traffic monitoring, weather sensing, and other municipal information gathering functions.

3. Solar Panels

Solar-powered systems reduce grid dependency while minimizing environmental impact through renewable energy integration.

The Right Light Dispersion for Street Lights

Proper installation techniques prevent glare while ensuring even light distribution for enhanced passenger safety. Light rays extending beyond 75 degrees from nadir create dangerous glare conditions for drivers. LED technology addresses this challenge through anti-glare design and balanced light output, while HPS fixtures produce problematic glare with light distribution extending beyond 150 degrees.

Wide-angled HPS installations demonstrate significant light waste, forcing nearby residents to draw curtains against unwanted illumination. This creates light pollution affecting astronomers and nature observers. LED fixtures eliminate this problem through focused, directional lighting that keeps illumination within target areas. Homes near LED-lit streets no longer require window coverings for privacy, and lower lumen requirements become possible since light reaches only intended surfaces.

Uniform Light Dispersion

Light uniformity becomes measurable only after installation completion. Achieving proper uniformity requires balancing optical properties, reflector quality, spacing between fixtures, and mounting considerations. Three key ratios determine dispersion quality:

• Average to minimum light intensity ratio
• Maximum to minimum light intensity ratio
• Maximum to average light intensity ratio

The first two measurements provide easier calculation methods, making them preferred for most applications. Uniform dispersion directly reduces glare by preventing pupil constriction that limits light reaching the eyes. While daytime methods like blinking, squinting, sunglasses, or visors help manage brightness, nighttime street users lack these options.

Comparison of High-Pressure Sodium and LED

Municipalities nationwide pursue enhanced safety through HPS to LED conversions. Beyond obvious energy efficiency advantages, additional factors require consideration. The National Lighting Product Information Program (NLPIP) analyzed these issues in comprehensive 2010 research examining eight street light samples from leading manufacturers:

1. LED fixtures produced lower initial output than labeled specifications suggested compared to target HPS replacements.
2. Energy savings remained substantial despite requiring closer spacing. Even with additional fixture quantities needed, LEDs maintained superior efficiency over HPS systems.
3. Manufacturers often recommend lower lumen LED fixtures, but proper replacement requires matching HPS output levels with appropriate LED lumen ratings and similar spacing patterns.

Initial LED conversion costs exceed traditional lighting investments significantly. However, NLPIP studies confirm that LED lifespan and operational efficiency far surpass conventional HPS technology, making LEDs the superior long-term street lighting solution.

What is the Cost of Street Light LED Conversion?

1. The Initial Cost of Items like Electrical Wires, Poles, and Bulbs, Plus Installation Cost

Single light pole installation averages approximately $4,000 per unit. Final costs vary based on pole height requirements, foundation specifications, electrical source distance, and fixture efficiency ratings. Rural installations often require longer wire runs to power sources, increasing material costs. Solar-powered alternatives eliminate grid connection expenses but carry higher upfront equipment costs.

2. Cost of energy consumption by the lights

Replacing metal halide fixtures with 100-watt LED lights produces approximately 15,550 lumens of superior quality illumination. Los Angeles operates around 209,000 street lights consuming roughly 197,000,000 kWh annually at 250 watts per hour average. This massive energy consumption drives municipal LED conversion initiatives across major cities.

3. Cost of Bulb Disposal and Changing Fused Bulbs

Maintenance and disposal expenses often get overlooked in lighting cost analysis. Los Angeles spends approximately $42 million annually maintaining 209,000 street lights, equating to $200 per fixture yearly. Elevated mounting heights require specialized equipment including cherry pickers and service trucks, driving up labor costs significantly.

U.S. Naval Observatory research by Christian B. Luginbuhl found LPS fixtures have roughly 6,000 fewer operating hours than HPS systems while requiring increased maintenance. Combined with poor color rendering capabilities, these factors make Low-Pressure Sodium unsuitable for most applications. Metal halide and HPS technologies typically provide 12,000 to 15,000 hours of service life, but suffer from significant lumen depreciation (L50) over time.

Calculating the Replacement Cost of One Bulb

Complete bulb replacement expenses include multiple components: new bulb and ballast costs ($150), two-person crew wages, man lift rental fees, and service truck expenses, totaling approximately $800 per replacement.

Budget-constrained municipalities must deliver quality lighting services within limited funding. Advanced lighting technologies address these challenges through remote monitoring systems that reduce physical maintenance requirements.

LED systems deliver exceptional value with average lifespans extending ten years beyond traditional alternatives. Cities like Ann Arbor benefit significantly from modern lighting technologies that minimize ongoing maintenance demands.

• Lumen Output: LED – 15,500 | High Pressure Sodium – 28,000 | Mercury Vapor – 28,000 | Incandescent – 5,600
• Watts: LED – 100W | High Pressure Sodium – 250W | Mercury Vapor – 400W | Incandescent – 400W
• Lumens per Watt: LED – 155 | High Pressure Sodium – 112 | Mercury Vapor – 70 | Incandescent – 14
• Wastage %: LED – 0.00% | High Pressure Sodium – 50% | Mercury Vapor – 50% | Incandescent – 50%
• Wasted Light (Lumens): LED – 0 | High Pressure Sodium – 14,000 | Mercury Vapor – 14,000 | Incandescent – 2,800
• Actual Light Availability (Lumens): LED – 15,500 | High Pressure Sodium – 14,000 | Mercury Vapor – 14,000 | Incandescent – 2,800
• Available Lumens per Watt: LED – 155 | High Pressure Sodium – 56 | Mercury Vapor – 35 | Incandescent – 7
• Hours of Operation per Night: LED – 10 | High Pressure Sodium – 10 | Mercury Vapor – 10 | Incandescent – 10
• Cost of Electricity ($/kWh): LED – $0.10 | High Pressure Sodium – $0.10 | Mercury Vapor – $0.10 | Incandescent – $0.10
• Annual Consumption (kWh): LED – 383 | High Pressure Sodium – 913 | Mercury Vapor – 1,460 | Incandescent – 1,460
• Annual Electricity Charges ($): LED – $38.3 | High Pressure Sodium – $91 | Mercury Vapor – $146 | Incandescent – $146
• Available Lumens per Dollar: LED – 411.9 | High Pressure Sodium – 153 | Mercury Vapor – 96 | Incandescent – 19
• Cost per 100 Lumens: LED – $0.24 | High Pressure Sodium – $0.65 | Mercury Vapor – $1.04 | Incandescent – $5.21
• Wastage (kWh): LED – 0 | High Pressure Sodium – 456.25 | Mercury Vapor – 730 | Incandescent – 730
• Wastage ($): LED – $0 | High Pressure Sodium – $45.63 | Mercury Vapor – $73 | Incandescent – $73
• Average Life Span (Years): LED – 20+* | High Pressure Sodium – 5 | Mercury Vapor – 4 | Incandescent – 3

Expert Support That Makes Your LED Conversion Decision Easier

LED Lighting Supply’s experienced product specialists eliminate the guesswork from your street lighting conversion project. Our photometric experts calculate exact energy savings based on your current system specifications and provide custom lighting plans tailored to your specific roadways and municipal requirements. With 17 years of commercial lighting expertise, our team analyzes your existing HPS fixtures, evaluates local Dark Sky ordinances, and recommends optimal LED replacements that meet both safety standards and budget constraints. We provide detailed ROI calculations showing your exact payback timeline based on current electricity rates and maintenance costs. This data-driven approach ensures your municipality makes informed decisions backed by precise engineering calculations rather than general estimates.