Solar Roadway Lighting: Which Road Types Are Suitable?

In the planning of the roadway lighting project, many engineering teams often fall into the trap of uniform configuration: using the same set of lighting equipment to adapt to all road scenarios. However, in reality, the traffic scenarios, safety standards, and lighting requirements for different levels of roads vary greatly. Residential area roads focus on pedestrian safety, while expressways prioritize the sight distance for high-speed driving and the reliability of traffic flow. There is no universal lighting solution that can adapt to all scenarios, and this is especially true for solar road lighting.

NOKIN will start from the classification of road levels and combine international common lighting standards to clearly break down the feasibility of solar lighting, configuration plans, and applicable boundaries for different levels of roads. It helps municipal engineering personnel, road contractors, and lighting designers quickly determine: which roads can be purely powered by solar energy, which need a mixed solution, and which must rely on grid power.

All lighting parameters in this article refer to the international road lighting standard ANSI/IES RP-8. However, the final implementation of solar road lighting projects must follow the local official regulations and is only used as a basis for scheme decision-making.

Road Classifications for Solar Roadway Lighting

The international road lighting system classifies roads into four core levels based on driving speed, traffic volume, service function, and safety level. Different levels directly determine the illumination standards, uniformity requirements, and power supply reliability thresholds, and are the underlying basis for judging the feasibility of solar lighting.

Core rule: The higher the road level, the higher the illumination requirements, the stricter the uniformity control, and the lower the tolerance for lighting interruptions.

Local Roads and Residential Streets

Low-speed traffic, small traffic volume, mainly for pedestrian and non-motorized vehicle travel. The core lighting goal is to enhance pedestrian safety and avoid short-distance travel safety hazards. The lighting standard threshold is the lowest.

Collector Roads and Branch Roads

Medium driving speed, medium traffic volume, mainly for the connection of residential areas and urban arterial roads, and also for the passage of pedestrians and vehicles. The lighting demand is moderate, and it is the core transitional road of the urban road network.

Urban Arterial Roads

High driving speed, large daily traffic volume, serving the main commuting of the city. The core lighting goal is to ensure vehicle traffic efficiency and avoid high-speed driving hazards, with strict requirements for illumination and uniformity.

Highways and Expressways

High driving speed, extremely large traffic volume, no pedestrian passage. It belongs to the highest-level transportation hub. It requires stable lighting 24/7 and zero tolerance for lighting interruptions. It is the highest level of road lighting standards and reliability requirements.

Solar Street Lighting Feasibility by Road Class

Combining IES RP-8 lighting standards, the characteristics of solar power supply load, stability of battery life, and project implementation experience, we have sorted out the feasibility of solar lighting for all road levels from three dimensions: illumination requirements, system load, and power supply reliability. We have discarded subjective judgment and all based on objective technical logic deduction.

Solar Street Light Configuration by Road Type

Road lighting effect is mainly determined by three parameters: pole height, light spacing, and light type selection. Based on the lighting requirements of different road grades, integrate standardized configuration schemes. All parameters are industry reference values. The final implementation requires verification through Dialux and AGi32 optical simulation.

Solar Roadway Lighting Standards: Illuminance and Uniformity

The two core hard indicators for road lighting compliance are average illumination and uniformity. Among them, uniformity is the most easily overlooked and the main reason for project non-compliance. The IES RP-8 standard clearly stipulates that different road grades must match corresponding illumination values and uniformity ratios.

Lighting Design Principles for Solar Roadway Compliance

Many people mistakenly believe that to improve lighting effect, the single light power must be increased. However, in professional roadway lighting design, light density + precise light distribution control are the core to meet the uniformity standard, rather than simply increasing the wattage of a single light.

Solar street lights can effectively eliminate light spots on the road surface by optimizing light light distribution angles and reasonably densifying light spacing. They can precisely match the uniformity requirements of different road grades, fully meeting international lighting standards.

Photometric Simulation and Lighting Compliance Verification

All formal solar road lighting projects must provide optical simulation reports and IES photometric documents before implementation. They can be rechecked and verified at any time to ensure that parameters such as illumination, uniformity, and glare restrictions are fully compliant.

It should be noted that the parameters in this article are general international standards references. Specific projects must strictly follow local municipal lighting regulations.

Which Roads Are Not Suitable for Standalone Solar Lighting?

Solar road lighting is not a universal solution. Clearly defining the adaptation boundaries is the key to the compliance, stability, and high cost-effectiveness of the engineering solution. Based on practical project experience, the following three scenarios are not recommended to be powered solely by solar energy.

High-Traffic Arterial Roads and Expressways

Urban arterial roads, expressways bear high traffic flow and high-speed traffic pressure. Lighting interruption will directly trigger major traffic safety accidents, belonging to zero-tolerance lighting scenarios. Independent solar systems are affected by weather and power supply capacity, unable to achieve 100% stable power supply throughout the year, unable to meet the reliability standards of high-grade roads.

Roads in Regions with Limited Solar Irradiance

High-latitude regions, continuous rainy and foggy areas, insufficient annual effective sunlight hours. The charging efficiency of solar panels has significantly declined, and the battery cannot guarantee sufficient power supply for night use. In winter, there are often problems such as insufficient lighting and power outages, making it impossible to meet the standards stably.

Roads with Low-Cost Grid Access

Urban core districts and road sections with full power grid coverage. The cost of power grid connection is extremely low and construction is convenient. Renovating solar lighting in such scenarios not only fails to highlight the advantages of no wiring and low cost, but also increases equipment procurement and maintenance costs, resulting in extremely poor economic performance.

Hybrid Solar and Grid Power for High-Traffic Roads

Non-core traffic sections such as expressway ramps, expressway service areas, and auxiliary roads of main roads can adopt a mixed power supply solution of "solar power as the main source, with grid power as a backup", balancing energy conservation and safety.

Most Cost-Effective Applications for Solar Roadway Lighting

The core advantage of solar roadway lighting is not simply energy saving and power consumption reduction, but avoiding the high cost of power grid wiring. For the following four types of road sections, the investment return rate of solar lighting is the highest, making it the optimal implementation scenario.

Roads with High Grid-Connection Costs

Road sections crossing farmland, rivers, forest reserves, and rocky terrains. Traditional power grid wiring requires road excavation, cable laying, and pipeline construction, with extremely high civil engineering costs. The cost per kilometer of wiring can reach several thousand dollars. Solar street lights do not require long-distance wiring, which can significantly reduce civil engineering expenses and shorten the construction period.

Rural Roads Without Grid Access

Remote rural roads and connecting roads between the city and suburbs. The cost of extending the power grid far exceeds the cost of purchasing lights. In such scenarios, using solar lighting eliminates reliance on municipal power grids, allowing for long-term use with a one-time investment, and the overall cost is much lower than the power supply scheme using municipal electricity.

Newly Built Roads and Temporary Traffic Routes

Newly planned roads, temporary construction passages, and short-term scenic roads. Municipal power supply requires cumbersome approval processes and construction periods. Solar street lights can be quickly installed and lit immediately, without the need for power approval, and are suitable for temporary and short-term lighting needs.

Core conclusion: The optimal implementation scenario for solar road lighting is not the urban core main roads, but the road sections with difficult power grid wiring, high connection costs, and complex approval processes.

Solar Road Lighting Project Checklist

To help engineering teams make quick and accurate decisions, avoid mistakes in solar lighting schemes, unqualified acceptance, and cost overruns, a standardized self-check list has been compiled. During project planning, each item can be checked one by one:

• Clearly define the road grade of the project and precisely match the corresponding illumination, uniformity, and power supply reliability standards
• Verify the annual solar conditions of the project location, focusing on evaluating the stability of power supply during winter and rainy seasons
• Calculate the distance to the on-site power grid and the cost of connection construction, and compare the overall cost of the solar solution
• Check for special construction conditions of the road section: crossing rivers, forest areas, no power grid, protected areas, etc.
• Determine whether to adopt a "solar power + grid power" mixed power supply solution to adapt to high-grade road sections
• Complete the optical simulation in Dialux/AGi32 to confirm that the lighting parameters are fully compliant

4 Common Solar Roadway Lighting Myths

In the implementation of solar roadway lighting projects, most problems are not due to equipment defects, but are caused by selection, design, and cognitive misunderstandings. The following clarifies the frequent misconceptions in the industry.

Myth 1: Solar Street Lights Are Not Bright Enough

The core reason for insufficient brightness is incorrect configuration and selection, rather than equipment performance defects. Residential areas and branch roads can meet the standards with standard solar lights; high-grade roads only need to be equipped with high-power split systems and optimized lighting layout to meet high illumination requirements.

Myth 2: All Roads Can Use Standalone Solar Lighting

Low and medium-grade roads are suitable for pure solar solutions, but high-grade roads such as expressways and urban core main roads, which have zero tolerance for reliability standards, are not recommended to use pure solar power supply. Blindly using it will cause significant safety hazards.

Myth 3: Higher Wattage Always Means Better Lighting

The wattage of a single light is merely a basic parameter. What truly determines the compliance of lighting is the light distribution design, the spacing of light placement, and the control of uniformity. Blindly installing high-wattage lights will cause light pollution and waste resources, and cannot improve the overall lighting quality.

Myth 4: No Trenching Means Zero Installation Costs

Solar street lights eliminate the process of digging and laying long-distance cables, but still require the completion of foundation pouring for light posts, and the fixation of the light posts. It is not zero construction or zero cost; the project budget should reasonably reserve relevant expenses.

Conclusion: Choosing the Right Solar Roadway Lighting Solution

The adaptability of solar road lighting is determined by three core variables: road grade, local sunlight conditions, and grid connection costs. The core decision-making logic of the industry is not "can solar energy be used", but "where is it most cost-effective and compliant to use solar energy".

For low-grade residential areas and side roads, solar energy is the optimal solution; for high-grade arterial roads and highways, pure solar energy solutions should be used with caution and a hybrid power supply mode should be preferred; for remote sections with difficult wiring and no grid connection, the value of solar lighting can be maximized.

If you are planning a road lighting project, please inform us of the road grade, road length, project location, and construction conditions. NOKIN will provide you with an exclusive feasibility analysis of solar lighting and precise equipment configuration plan.