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Why calculate the luminance uniformity of wet road surfaces?

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Why is it necessary to calculate the luminance uniformity of wet road surfaces?

Recently, someone asked me why there are two values of Uo in the road lighting requirements given by the client.
Indeed, why are there two Uo values?
Why calculate the luminance uniformity of wet road surfaces?
The road lighting standard we are most familiar with is the CJJ45-2015 “Design Standard for Urban Road Lighting,” which is widely used in our country. In this standard, Uo refers to the overall uniformity of road surface luminance.
Uo reference image
Moreover, there is only one Uo value in this standard.
So, why does the aforementioned client’s request include two Uo values?
This leads us to the international standard CIE115/EN13201.
In the requirements provided by the client, the road classification is A1, which immediately indicates that the applicable road classification standard is EN13201-1:2004. Those who have used DIALux 4.13 should be quite familiar with this standard.
Only in the EN13201:2004 road classification is there an A1 level.
EN13201 A1 level classification
By the time we reach 13201-1:2014, the road classifications have changed completely.
Changes in road classification EN13201-1:2014
The illumination standard corresponding to 13201-1:2014 is EN 13201-2:2003, where the roadway lighting standards are as follows.
Road lighting standard EN 13201-2:2003
Wait, there is still only one overall luminance uniformity Uo. So, where is the other Uo? Don’t worry, if we look closely at the table, it specifies dry road surface conditions, which means there is also a standard for wet road surfaces.
Dry vs. Wet road surface standards
Correct, the standard level for a dry roadway surface is ME, while the standard for a wet roadway surface is MEW, where the “W” stands for wet.
Standard levels for dry and wet surfaces
In this table, we find two Uo values: one for dry conditions with a minimum Uo value of no less than 0.4 and another for wet conditions with a minimum Uo value of no less than 0.15.
Uo values for dry and wet road conditions
Since this is based on the EN13201-2:2003 standard, it means that illumination calculations can be completed using DIALux 4.13, which integrates the road lighting standards from 13201-2:2003. If using the 2015 version, DIALux evo would be required.
Now let’s try to calculate the lighting for this road according to the conditions.
Initial road lighting calculation setup
According to client requirements, select the new street design case in the English interface, and then set the road conditions.
Road condition settings in DIALux
After setting the road conditions, select the luminaire photometric distribution. Based on the four-lane dual-directional road width, we prioritize Type III distribution and select either M or S distribution based on the ratio of pole spacing to pole height.
Luminaire photometric distribution selection
↑ This distribution is provided by DARKOO, featuring a glass lens material.
Importing selected luminaire distribution files
Import the selected luminaire photometric file and arrange the luminaires as per the client’s requirements.
Set the lighting standards and verify if the standard values match the requirements.
Set the optimization conditions and proceed with the optimization.
Optimization settings in DIALux
Optimized results display
The optimization results indicate that the Over hang between 1-2m satisfies the requirements. We will choose the shortest Over hang to save on pole material.
Import the results and calculate the final outcome.
Final results of the lighting calculation
This yields the calculation results that meet the client’s conditions, allowing us to export the report.
At this point, some may question why there are no requirements for wet road surfaces in domestic road lighting standards. Is it necessary to calculate for wet surfaces?
Actually, the “CJJ 45-2015 Design Standard for Urban Road Lighting” mentions that “the illumination indicators under dry conditions do not meet those under wet conditions. For instance, the overall uniformity of brightness, where a dry condition Uo of 0.4 makes it very difficult to reach 0.2 under wet conditions, yet no standard values for wet road surfaces are given.
The road surface standards in CIE115/EN13201 are set in accordance with CIE 47-1979 “Road Lighting for Wet Conditions.” This standard includes 4 tables in the R series, 4 in the N series, 2 in the C series, and 4 in the W series, to meet rough road surface luminance calculation needs.
However, most of these standard data tables originate from studies conducted by European scientists in the 1960s and 1970s on typical road materials of that time, which differ significantly from the road materials currently in widespread use in China. Due to the lack of research on the reflective characteristics of road materials domestically, there is currently no standard reflectance data for road materials in China. Thus, our domestic standards have not set illumination standards for wet road surfaces.
Of course, this does not imply that the illumination indicators for wet road surfaces are unimportant; in fact, they are quite crucial.
Importance of wet road surface illumination
As shown in the above image, the last image’s luminance uniformity for wet road surfaces differs greatly from that of dry road surfaces, significantly affecting drivers.
Friends who have driven on rainy nights should all have the experience that the visibility on rainy roads is indeed very poor.
Visibility on wet roads during rain
Thus, there should be standards for road surface illumination indicators for wet conditions.
Solar Street Light Color Rendering Index

Solar Street Light Color Rendering Index (CRI) Application Guide – Manufacturer’s Perspective

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Understanding the Color Rendering Index (CRI) in Solar Street Lights

The Color Rendering Index (CRI) is a crucial parameter for evaluating the color rendering performance of solar street light sources. The higher the CRI, the better the color reproduction, and the visual effect is closer to natural light. This article analyzes the CRI values of different types of light sources and their impact on visual quality.

As a solar street light manufacturer, we understand that CRI directly affects lighting effects and user experience. Below, we provide practical advice from the perspectives of technical principles, scene adaptation, and product selection.

Solar Street Light Color Rendering Index

1. Comparison of Light Source Types and Color Rendering Characteristics

Light Source TypeCRI (Ra)Spectral CharacteristicsAdaptability Assessment (Solar System)
Incandescent Lamp95-100Continuous spectrum, but lacks blue lightBest color rendering but only 15lm/W efficiency, requires 3x battery capacity, now obsolete
Fluorescent Lamp60-85Line spectrum, lacks red lightDifficult to start at low temperatures (-10℃ brightness drops by 40%), not suitable for cold regions
High-Pressure Sodium Lamp20-25Narrow spectrum yellow light, severe color distortion100lm/W+ efficiency, only used in remote low-cost projects
LED Lamp70-98Adjustable full spectrum/segmented spectrumMainstream choice, high CRI models offer 130lm/W+ efficiency, controllable energy consumption

2. Impact of Solar Street Light CRI on Actual Effects

Safety and Functionality

  • Low CRI (Ra<70): Red warning signs ΔE color difference >15 (international requirement ΔE<5), face recognition distance shortened by 30%.
  • High CRI (Ra≥80): Vegetation layering improves by 50%, reduces “spooky feeling” complaints at night.

Economy and Energy Efficiency

  • For every 10-point increase in Ra: Requires an 8% increase in battery capacity (e.g., 50W street light Ra70→Ra80 requires an additional 10Ah battery).
  • Cost balance: High CRI LED premium is about 0.8-1.2 yuan/W, but maintenance cycle extends by 2-3 years.

Commercial Value

  • Ra≥90: Product color saturation increases by 18%, night-time consumer conversion rate increases by 12% (measured data from commercial squares).

Solar Street Light Color Rendering Index

3. Scenario-Based Selection Scheme

Application ScenarioRecommended Ra ValueKey Technical SolutionCost Sensitivity
Suburban Main Road70-753000K warm white light + asymmetric lens, reduces blue light spill★★☆☆☆
Old Residential Area80-85R9 supplementary light chip (deep red restoration) + anti-glare design★★★☆☆
Cultural Tourism Landscape Belt90-95Full spectrum LED + RGBCW intelligent color adjustment, restores ancient building textures★★★★☆
Industrial Park65-70High efficiency low CRI models, emphasizes uniform illumination★☆☆☆☆

Engineering Suggestions:

  • Key area testing: Use X-Rite CA410 spectrophotometer to measure R9 (deep red) and R12 (deep blue) performance.
  • Hybrid solution: Basic module (Ra70) + key supplementary light module (Ra90), balances cost and effect.

4. Technical Optimization and Quality Control Points

Spectral Enhancement Technology

  • Violet-excited LED: Spectral continuity and similarity to sunlight reaches 92%, Ra≥95 and blue light peak reduced by 40%.
  • Dynamic dimming: Automatically switches to low CRI mode (Ra85→70) during low traffic periods, extends battery life by 30%.

Attenuation Control

  • Annual attenuation standard: High-quality products CRI annual decline ≤1.5, low-quality products can reach 5-8 points.
  • Compensation circuit: Built-in current regulation module, offsets color rendering decline caused by LED chip aging.

Optical Design

  • Compound lens: Secondary light distribution reduces invalid scattering, increases effective color rendering light by 15%.

5. User Purchase Suggestions

  1. Certification standards: Request CIE S 025/E:2015 test report, focus on Rf (fidelity) and Rg (gamut index).
  2. Warranty terms: Choose manufacturers that promise “Ra decline ≤3 within 5 years”, prioritize products supporting modular upgrades.
  3. On-site verification: Use standard color cards (e.g., ColorChecker 24 colors) to compare lighting effects before installation.

Case reference: A certain ancient town project used LED with Ra95+R9>60, increasing night-time visitor stay time by 1.2 hours and shop revenue by 18%.

As a manufacturer, we recommend users choose a “sufficient and economical” color rendering solution based on actual needs, avoiding the cost waste brought by blindly pursuing high parameters. For customized solutions, we can provide spectrum simulation and energy consumption calculation services.

Tag: Solar Street Light CRI

LUXMAN SOLAR STREET LIGHT MANUFACTURER

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Luxman Light puts its customers and quality first. The team boasts a wealth of experience with decades of hands-on knowledge in the lighting and new energy space.

As a global leader in photovoltaic lighting, Luxman partners with businesses to customize innovative power and sustainability solutions that are informed by many years of experience at the cutting-edge of photovoltaics.

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SOLAR STREET LIGHT MANUFACTURER