LED street lighting is a road lighting device with an LED light source as the core. It features high efficiency and energy savings, long lifespan, and intelligent control, among other benefits. It is primarily used to replace traditional streetlights, reducing energy consumption and improving lighting quality.
- What is the LED street lighting solution?
- LED street lighting uses and scenarios?
- What are the common LED street lighting solutions?
- What is the brightness requirement for urban secondary trunk road/branch road lighting solutions?
- How to determine the installation spacing and height of lamps?
- How to ensure the balance between lighting effect and energy consumption in road lighting design?
- In rural road lighting design, how should different types of lamps be selected?
What is the LED street lighting solution?
LED street lighting solutions are based on LED (light-emitting diode) light source technology, and are an overall solution for systematic planning, design, equipment selection and implementation for lighting needs in urban roads, rural roads, park roads and other scenes. Its core goal is to achieve advantages such as energy saving, intelligent control, long life and environmental adaptation on the premise of meeting basic requirements such as road lighting brightness, uniformity and safety.
Core components of the solution
A complete LED street lighting solution usually includes the following key parts:
1. Lighting demand analysis (preliminary research)
It is necessary to clarify the basic parameters in combination with the road type to ensure that the solution is suitable for the scene:
Road type: such as main roads (large traffic volume and high speed), secondary roads, branch roads, sidewalks, rural roads, etc. (different types have different brightness requirements).
Basic parameters:
Brightness: 15-30cd/㎡ is usually required for main roads, and 5-10cd/㎡ for branch roads (avoiding excessive glare or too dark to affect safety);
Uniformity: The road surface brightness uniformity (minimum brightness/average brightness) must be ≥0.4 to avoid alternating light and dark affecting vision;
Glare control: Use cut-off or semi-cut-off lamps to limit direct strong light (such as the glare index UGR of the driver's perspective must be ≤19);
Illumination range: Determine the illumination angle of the lamp according to the width of the road and the number of lanes (such as 120° wide angle is suitable for wide roads, 60° narrow angle is suitable for narrow roads).
Environmental factors: such as whether there are trees blocking, whether it is close to residential areas (night light pollution needs to be considered), extreme weather (high-grade lamps are required in high-temperature, severe cold, and rainy areas).
2. Selection of LED lamps
The lamps are the core equipment of the solution, and the following parameters should be paid special attention to:
Light source performance:
Light efficiency: lamps with ≥130lm/W are preferred (ordinary high-pressure sodium lamps are about 80lm/W, saving more than 50% energy);
Color temperature: 3000K-4000K (warm white light or neutral light, strong penetration, visual comfort) is recommended for main roads, and cold white light above 6500K should be avoided (easy to produce glare and affect night vision);
Color rendering index (Ra): ≥60 (can clearly distinguish road obstacles, pedestrians and traffic signs).
Lamp structure:
Protection level: IP65 (dustproof + low-pressure water spray proof) is required for outdoor use, and IP66 is recommended for humid areas;
Material: The lamp body is made of aluminum alloy (good heat dissipation) + tempered glass (impact-resistant), avoiding plastic shell (easy to age);
Heat dissipation design: Through fin-type heat dissipation, heat pipe heat dissipation and other structures, ensure that the operating temperature of the LED chip is ≤60℃ (excessive temperature will greatly shorten the life).
Power matching: Select the power according to the road width and brightness requirements, for example:
Main road (width 15-20 meters): 150-200W lamps;
Branch road (width 5-10 meters): 50-100W lamps;
Sidewalk: 30-50W lamps.
3. Lighting design (installation planning)
The installation location and method of the lamps should be determined in combination with the actual layout of the road to ensure that there is no blind spot in the lighting coverage:
Installation height: The height of the lamps from the ground is usually 6-12 meters (8-12 meters for main roads and 6-8 meters for branch roads), to avoid insufficient brightness due to too high a height or glare due to too low a height.
Installation spacing: Determined according to the lamp power and irradiation angle, generally 3-5 times the installation height (e.g. 10-meter-high lamps, 30-50 meters apart), to avoid dark areas due to too large a spacing.
Lighting method:
Single-side lighting: suitable for narrow roads (width ≤ 10 meters), lamps are installed on one side of the road;
Symmetrical lighting on both sides: suitable for medium-width roads (10-15 meters), lamps are installed symmetrically on both sides;
Staggered lighting on both sides: suitable for wide roads (≥15 meters), lamps are installed in staggered positions on both sides to reduce shadows;
Central lighting (such as lighting in isolation belts): suitable for ultra-wide main roads, lamps are centered to illuminate the lanes on both sides.
4. Intelligent control system (optional, improves energy saving and management efficiency)
Modern solutions are often combined with intelligent control to achieve "on-demand lighting":
Basic functions:
Time control: automatically turn on and off lights according to sunrise and sunset (such as 19:00 on and 5:00 off in summer, 17:30 on and 6:30 off in winter);
Light control: sense the ambient brightness through photosensors and automatically adjust the power (such as turning on the lights in advance in the evening on cloudy days, and reducing the power to 70% when there are few cars in the second half of the night);
Remote control: remotely monitor the status of lamps (fault alarm, brightness adjustment) through the Internet of Things (IoT) platform, without manual inspection.
Advanced functions:
Traffic flow sensing: detect vehicles through radar or cameras, turn on the lights at full power when vehicles come, and reduce the power when there are no vehicles (saving more than 30%);
Single lamp control: each lamp is independently connected to the Internet, and the brightness can be adjusted or faults can be checked separately.
5. Power supply and line design
Power supply mode:
Conventional power grid power supply: suitable for urban roads (distribution boxes and cable laying paths need to be designed to avoid conflicts with other pipelines);
Solar + energy storage power supply: suitable for rural roads without grid coverage (sunshine duration needs to be calculated, solar panel power and battery capacity need to be matched to ensure normal operation on continuous rainy days).
Line protection: Cables need to be buried in PVC pipes or galvanized steel pipes (depth ≥ 0.7 meters) to avoid being crushed or corroded; waterproof and sealed lamp wiring points.
6. Cost and benefit calculation
Initial cost: lamp purchase (accounting for 60%-70%), installation and construction, control system, cables, etc.;
Long-term benefits:
Energy saving: Compared with traditional high-pressure sodium lamps, LED lamps reduce energy consumption by 50%-70% (100W LED ≈ 250W sodium lamp brightness);
Maintenance: LED life is 50,000-100,000 hours (sodium lamps are only 10,000-20,000 hours), reducing replacement costs (such as 100 lamps, 5-8 fewer maintenance times per year);
Investment payback period: usually 3-5 years (energy saving + maintenance savings cover initial investment).
Advantages of the solution (compared with traditional sodium lamps)
| Comparison Items | LED Street Lights | Traditional high high-pressure sodium lamp |
|---|---|---|
| Energy consumption | Low (energy saving 50%-70%) | high |
| life | 50,000-100,000 hours (5-8 years) | 10,000-20,000 hours (1-2 years) |
| Brightness Control | Support dimming (intelligent adaptation) | Cannot dim (fixed power) |
| Startup speed | Instant start (no preheating required) | 5-10 minutes to warm up |
| Environmental protection | No mercury, no UV pollution | Contains mercury, which can easily pollute the environment after being discarded |
| Color rendering) | Good (Ra ≥ 60, see the details of the object clearly | Poor (Ra≈20, color distortion) |
Typical application scenarios
Urban trunk roads: 200W LED lamps (4000K color temperature), staggered lighting on both sides (10 meters in height, 40 meters in spacing), with traffic flow sensor control (reduced to 120W when no car), meet the brightness of 20cd/㎡, and save 60% energy annually;
Rural roads: 60W solar LED lamps (3000K color temperature), single-sided lighting (6 meters in height, 30 meters in spacing), no power grid required, suitable for remote areas, and can last for 3-5 days in rainy weather.
LED street lighting uses and scenarios?
LED street lighting has become the mainstream choice for lighting of various roads and public areas due to its advantages of energy saving, long life, high light efficiency and strong controllability. Its core purpose is to ensure the safety of night travel, improve environmental visibility, and adapt to the functional requirements of different scenarios (such as energy saving, light pollution prevention, intelligent management, etc.). The following is a detailed description from the two aspects of specific uses and typical scenarios:
Core Uses
Basic Safety Lighting
This is the most core use: by providing uniform and moderate brightness, pedestrians and vehicles can clearly identify road conditions (such as obstacles, potholes), traffic signs (traffic lights, zebra crossings) and surrounding environment (pedestrians and other vehicles) at night, reducing collisions, falls and other safety accidents.
For example: the main road needs to ensure that the driver of a high-speed vehicle can find the object in front 50-100 meters in advance; the sidewalk needs to allow pedestrians to see the details such as the steps and manhole covers on the road.
Traffic guidance and order maintenance
Through lighting, the visibility of road boundaries (such as lane lines, curbs) and traffic facilities (such as isolation belts, signal lights) is enhanced to guide vehicles and pedestrians to pass according to the rules and avoid behaviors such as driving in the opposite direction and occupying the road due to blurred vision.
Energy saving and cost optimization
Compared with traditional high-pressure sodium lamps, LED street lamps reduce energy consumption by 50%-70%, and have a lifespan of 50,000-100,000 hours (3-5 times that of sodium lamps), which can greatly reduce electricity bills and lamp replacement and maintenance costs, especially suitable for large-scale public lighting scenarios.
Intelligent management adaptation
Support linkage with intelligent control systems (such as time control, light control, and vehicle flow sensing) to achieve "on-demand lighting" (such as reducing power when there are few cars in the second half of the night, and low brightness during no-car periods), further saving energy; at the same time, remote monitoring of faults can be carried out to improve management efficiency.
Environmental friendliness and light pollution control
LED light source spectrum is controllable (no ultraviolet light, no mercury), and the lamps can be designed to cut off light (avoid direct light to residential areas or the sky), reducing light pollution to the surrounding environment (such as not affecting residents' night rest and not interfering with astronomical observations).
Typical application scenarios and adaptation requirements
The road types, traffic volume, and pedestrian density of different scenarios vary greatly, and the requirements for the brightness, power, and lighting methods of LED street lights are also different, as follows:
1. Urban main roads (including expressways)
Scenario characteristics: large traffic volume, high speed (60-80km/h), wide roads (15-30 meters, mostly 4-8 lanes), and the need to clearly identify road conditions and traffic signs at a long distance.
Lighting requirements:
Brightness: 15-30cd/㎡ (average brightness), ensuring that drivers can see obstacles clearly at 50 meters away;
Lamps: 150-200W high-power LED, color temperature 3000K-4000K (warm white/neutral white, strong penetration), cut-off design (reduce glare);
Lighting: staggered on both sides or in the center isolation belt (height 10-12 meters, spacing 30-40 meters).
Example: urban expressway, main road connecting the main urban area and suburbs.
2. Urban secondary road
Scene characteristics: medium traffic volume (speed 40-60km/h), wide road (10-15 meters, 2-4 lanes), taking into account the needs of vehicles and pedestrians.
Lighting requirements:
Brightness: 10-15cd/㎡, uniformity ≥0.4;
Lamp: 100-150W LED, color temperature 3000K-4000K, half-light type (allowing a small amount of light to illuminate the curb);
Lighting: bilateral symmetry or single-side lighting (height 8-10 meters, spacing 25-35 meters).
Example: Regional roads connecting main roads and branch roads in the city (such as main roads around residential areas).
3. Urban branch roads and alleys
Scene characteristics: small traffic volume (speed ≤30km/h), narrow roads (5-10 meters, 1-2 lanes), many pedestrians, and need to avoid excessive brightness that affects surrounding residents.
Lighting requirements:
Brightness: 5-10cd/㎡ (avoid glare);
Lighting: 50-100W LED, color temperature 2700K-3000K (warm white light, soft and non-disturbing);
Lighting: single-side lighting (height 6-8 meters, spacing 20-30 meters), can be matched with intelligent light control (power reduced to 50% after 12 o'clock at night).
Example: internal roads in residential areas, alleys in old urban areas, and branch roads around vegetable markets.
4. Sidewalks and pedestrian streets
Scene characteristics: no motor vehicles (or only low-speed non-motor vehicles), dense pedestrians, need to see road details (such as steps, manhole covers, obstacles), and the atmosphere needs to be comfortable.
Lighting requirements:
Brightness: 3-5cd/㎡ (avoid being too bright to dazzle the eyes, and not too dark to cause tripping);
Lighting: 30-50W low-power LED, color temperature 2700K-3000K (warm white light, warm feeling), anti-glare design (light is tilted toward the ground and does not shine directly into pedestrians' eyes);
Lighting: installed along the edge of the sidewalk (height 3-6 meters, spacing 15-25 meters), can be combined with landscape design (such as modeling lamps).
Examples: Commercial street pedestrian street, park trail, riverside/riverside sidewalk.
5. Rural roads and township roads
Scene characteristics: small traffic volume (mostly agricultural vehicles and private cars), narrow roads (3-8 meters), may not be covered by the power grid, low cost and easy maintenance are required.
Lighting requirements:
Brightness: 5-10cd/㎡ (just enough for basic recognition, no need for excessive brightness);
Lamp: 50-100W LED, preferably solar + energy storage (no need to pull the power grid, suitable for remote areas), protection level IP66 (anti-rainstorm, sand and dust);
Lighting: single-side lighting (height 6-8 meters, spacing 25-40 meters), can simplify control (only light control or time control).
Example: highways connecting towns and villages, and roads around rural industrial parks.
6. Special scene roads
Tunnel entrance/exit: It is necessary to avoid the "light and dark adaptation problem" and adopt a gradual brightening/darkening design (the brightness of the entrance section is gradually reduced to the standard in the tunnel, and the brightness of the exit section is gradually increased), the lamp power is 100-200W, and the color rendering index Ra≥70 (traffic signs can be seen clearly).
Bridges and flyovers: Consider the windy and humid environment. The protection level of the lamps should be IP66 or above. The lamps should be installed along the guardrails or piers to avoid shadows (for example, the lower level of the flyover needs additional lighting to prevent it from being blocked by the upper level).
Campus/park internal roads: Taking into account both lighting and atmosphere, low-brightness (5-8cd/㎡), styling LED lamps can be used, with intelligent control (power reduction after 10 pm).
Summary
The essence of the purpose of LED street lights is to "provide safe, energy-saving, and scene-adaptive lighting on demand", and the core differences in scenes are traffic volume, speed, road width, pedestrian density and environmental conditions. By matching the brightness, power, lighting methods and additional functions (such as intelligent control and solar power supply) of different scenes, LED street lights can not only meet basic safety needs, but also achieve energy saving and management optimization, and are the preferred solution for various types of road lighting.
What are the common LED street lighting solutions?
The design of LED street lighting solutions needs to be combined with factors such as road type, functional requirements (such as energy saving, intelligent management), environmental conditions (such as whether there is a power grid, climate characteristics), etc. Common solutions can be divided into the following categories according to core design goals or technical characteristics. Each type of solution has a clear applicable scenario and implementation logic:
Conventional solutions are divided by "basic functional requirements"
This type of solution is the most common application form, with the core of meeting basic lighting + adapting to road types, focusing on matching the brightness and power requirements of road grades (such as main roads and branch roads).
1. Urban main road/expressway lighting solution
Core goal: to ensure the long-distance vision (50-100 meters) of high-speed vehicles and reduce glare and visual fatigue.
Solution design:
Lamp selection: 150-200W high-power LED street lamp (luminous efficiency ≥130lm/W), color temperature 3000K-4000K (warm white/neutral white, strong penetration), cut-off lamp (shading angle ≥30° to avoid direct light into the driver's eyes).
Lighting method: staggered lighting on both sides (when the road width is ≥15 meters) or lighting in the central isolation belt, installation height 10-12 meters, spacing 30-40 meters (to ensure that there is no obvious shadow on the road surface).
Brightness requirements: average brightness 15-30cd/㎡, brightness uniformity ≥0.4 (to avoid visual discomfort caused by alternating light and dark).
Applicable scenarios: urban expressways, main roads connecting the main urban area (such as two-way roads with more than 6 lanes).
2. Urban secondary roads/branch road lighting plan
Core goal: balance vehicle traffic and pedestrian safety, and take into account energy saving (no need for excessive brightness).
Design:
Lighting selection: 100-150W LED street lights, color temperature 3000K-4000K, half-cut light type (allowing light to cover the curb, convenient for pedestrians).
Lighting method: bilateral symmetrical lighting (road width 10-15 meters) or single-sided lighting (width <10 meters), height 8-10 meters, spacing 25-35 meters.
Brightness requirements: average brightness 10-15cd/㎡ (secondary trunk road) or 5-10cd/㎡ (branch road), uniformity ≥0.3.
Applicable scenarios: secondary trunk roads around residential areas, branch roads in old urban areas, auxiliary roads in commercial areas.
3. Sidewalk/pedestrian street lighting plan
Core goal: to ensure that pedestrians can see the details of the road surface (steps, manhole covers), avoid glare, and create a comfortable atmosphere.
Solution design:
Lamp selection: 30-50W low-power LED, color temperature 2700K-3000K (warm white light, soft and not dazzling), diffuse reflection lamps (light tilted to the ground, irradiation angle ≤60°).
Lighting method: installed along the edge of the sidewalk or green belt, 3-6 meters high, 15-25 meters apart (to ensure that there is no shadow dead corner on the road surface).
Additional design: can be combined with landscape shape (such as lantern-style, simple line lamps) to enhance aesthetics.
Applicable scenarios: commercial street pedestrian street, park trail, riverside/riverside sidewalk.
Optimization scheme divided by "energy saving and intelligent management"
This type of scheme adds energy-saving control or intelligent linkage to basic lighting, which is suitable for scenarios with high requirements for operating costs and management efficiency.
1. Intelligent dimming energy-saving scheme
Core logic: Dynamically adjust the brightness according to "time period, traffic flow, and light" to avoid energy waste of "full power lighting all night".
Scheme design:
Control method:
Time control + light control: automatically turn on the light in the evening (light < 5lux), reduce the power to 50%-70% in the middle of the night (such as after 23:00), and restore full power in the early morning (such as after 5:00);
Traffic flow sensing: through radar or camera detection, maintain 30% power during the car-free period, and increase to 100% power within 1 second when a car passes (delayed 30 seconds and then fall back).
Hardware configuration: LED lamps with built-in dimming driver (support 0-10V or PWM dimming) + intelligent controller (support LoRa/NB-IoT wireless communication).
Energy saving effect: 30%-50% power saving compared to traditional solutions, suitable for roads with large differences in traffic flow during the day and night (such as suburban main roads and industrial park areas).
2. Solar LED Street Light Solution
Core logic: Use solar energy to generate electricity and get rid of grid dependence, suitable for remote areas without power supply or high electricity costs.
Solution design:
Component configuration: LED lamps (30-100W, depending on road requirements) + solar panels (power is 2-3 times that of lamps to ensure energy storage) + lithium batteries (capacity to meet 3-5 rainy days) + light control / time control controller.
Installation requirements: Solar panels are tilted 30°-45° to the south (maximum lighting), and the lamp protection level is IP66 (anti-rainstorm, sand and dust).
Applicable scenarios: rural roads, remote scenic roads, newly developed parks (not yet connected to the grid).
Note: It is necessary to calculate the local sunshine duration in advance (such as areas with an average annual sunshine of <4 hours, be cautious and may need to be equipped with city power backup).
3. Comprehensive solution for smart street lights
Core logic: Based on LED lighting, integrate additional functions such as "monitoring, communication, and environmental monitoring" to achieve "one pole for multiple uses".
Solution design:
Basic lighting: Same as conventional solution (select power and light arrangement according to road grade);
Additional functions:
IoT module: remote monitoring of lamp status (automatic alarm for faults);
Security monitoring: cameras capture traffic violations and abnormal events in real time;
Environmental monitoring: detection of PM2.5, noise, temperature and humidity (data uploaded to the city management platform);
5G micro base station/WiFi coverage: provide communication signals for the surrounding area (suitable for commercial areas and densely populated areas).
Applicable scenarios: smart city pilot areas, core commercial areas, and roads around transportation hubs.
Special solutions divided by "special environment adaptation"
For special scenarios such as tunnels, bridges, rainy and foggy areas, problems such as "light adaptation and environmental protection" need to be solved.
1. Tunnel lighting solution
Core pain point: The difference in lighting inside and outside the tunnel is large ("black hole effect"), which can easily lead to visual adaptation difficulties for drivers; and the tunnel is humid and dusty, requiring high protection of lamps.
Solution design:
Segmented lighting:
Entrance section: The brightness gradually decreases (such as the brightness within 10 meters of the entrance = 80% of the natural light outside, and decreases by 20% every 10 meters inside) to avoid "instant dimming";
Middle section: Maintain stable brightness (5-10cd/㎡), lamps 100-150W, color temperature 4000K (strong penetration);
Exit section: The brightness gradually increases (close to the natural light outside).
Lamp requirements: Protection level IP65 or above (moisture-proof and dust-proof), vibration-resistant (adapt to the airflow impact of vehicles passing).
2. Lighting solutions for bridges and rainy and foggy areas
Core pain points: bridges are windy and prone to water accumulation; rainy and foggy areas require strong light penetration to avoid "glare + fog scattering" affecting vision.
Solution design:
Lamp selection: color temperature 3000K (warm white light, better fog penetration than cold white light), protection level IP66 (anti-rainstorm, anti-salt spray corrosion, coastal bridges need to add anti-corrosion coating).
Lighting method: install along the bridge guardrail or pier to prevent the lamps from being blown off by the wind; height 8-10 meters, spacing 25-35 meters (reduce shadows).
Additional design: add anti-glare panels to the lamps (reduce direct light to the driver's eyes).
The core of common LED street lighting solutions is "on-demand design" - select matching lamps, lighting methods, and control logic according to road grade (traffic flow, speed), environmental conditions (whether there is a power grid, climate), and management needs (energy saving, intelligence). The basic solution meets the requirement of "safe lighting", the optimization solution improves "energy saving and management efficiency", and the special solution solves the "pain points of special environments". In practical applications, multiple solutions (such as "main roads + smart dimming" and "rural roads + solar energy") are often combined to achieve the best effect.
What is the brightness requirement for urban secondary trunk road/branch road lighting solutions?
The lighting brightness requirements for urban secondary roads and branch roads vary according to different standards, as follows:
Average brightness: According to the "Road Lighting Design Specifications", the average brightness of secondary roads is 0.75-1.0cd/m², and the average brightness of branch roads is 0.5-0.75cd/m².
Average illumination: According to the "Road Lighting Design Specifications", the average illumination maintenance value of secondary roads is 10-15lx, and the average illumination maintenance value of branch roads is 8-10lx. If it is a cement concrete pavement, its average illumination value can be reduced by about 30% accordingly. In addition, some data also show that the illumination of the secondary road pavement is 15-20lx, and the illumination of the branch road pavement is 5-10lx or 10-15lx.
How to determine the installation spacing and height of lamps?
The installation spacing and height of lamps are the core parameters of road lighting design, which directly affect the brightness uniformity, lighting effect and energy consumption of the road surface. It needs to be determined comprehensively in combination with road width, lamp light distribution type, light source power, and reference lighting standards (such as average brightness, illumination uniformity), while taking into account the differences in different scenes (urban, rural, special sections). The following are specific methods and principles:
Core design basis: clarify "basic parameters"
Before determining the spacing and height, 3 key parameters must be clarified:
Road width (W): the basis for determining the coverage range of lamps (such as rural branch roads are 2-3 meters wide and urban secondary roads are 8-12 meters wide).
Lamp light distribution type: Different light distribution determines the light diffusion angle (affecting the coverage width), common types:
Narrow light distribution: concentrated light (horizontal diffusion angle ≤ 60°), suitable for narrow roads (such as rural branch roads, sidewalks), small coverage width but concentrated brightness.
Medium light distribution: horizontal diffusion angle 60°-90°, suitable for medium-width roads (such as urban branch roads and rural main roads), balancing coverage and brightness.
Wide light distribution: horizontal diffusion angle ≥90°, suitable for wide roads (such as urban main roads and squares), with large coverage but easy brightness attenuation.
Target brightness/illuminance: determined according to the road type (such as the average illumination of rural branch roads 1-3lx, urban secondary roads 10-15lx), the higher the brightness requirement, the smaller the spacing may need to be.
Determination of installation height (H): "coverage width + avoid glare"
The installation height refers to the vertical distance from the luminous center of the lamp to the road surface, which must meet two core requirements:
Cover the full width of the road and avoid dark areas at the edge;
Avoid glare (too low height is easy to directly hit the human eye, too high will cause serious brightness attenuation).
1. Basic formula (reference)
The height (H) must be ≥ 0.8-1.2 times the road width (W) (adjusted according to the lighting type):
Narrow lighting: H ≈ W (because the light is concentrated, the height must be close to the road width to cover the entire width);
Medium lighting: H ≈ 0.8-1.0×W (the light is slightly diffused, and the height can be slightly lower than the road width);
Wide lighting: H ≈ 0.6-0.8×W (the light is widely diffused, and a lower height can cover a wide road).
2. Reference values for different scenarios
| Road Type | Road width (W) | Light distribution type | Recommended installation height (H) | Remark |
|---|---|---|---|---|
| Rural branch road | 1-3 meters | Narrow light distribution | 3-5 meters | Mainly for pedestrians and non-motor vehicles, the height should not be too high (to avoid brightness attenuation) |
| Rural main road | 3-6 meters | Middle light distribution | 5-6 meters | Need to cover the entire road width, taking into account small vehicles |
| City branch road | 6-8 meters | Middle light distribution | 6-8 meters | When lighting on one side, the height needs to be slightly higher |
| Urban secondary roads | 8-12 meters | Medium / Wide Light Distribution | 8-10 meters | The height of a single lamp can be lowered when lighting on both sides |
3. Special restrictions
The height should not be too low: avoid the lamp being blocked by trees or buildings, or being hit by pedestrians or vehicles (such as rural road height ≥3 meters, urban road ≥5 meters);
The height should not be too high: after exceeding 12 meters, the light attenuation is serious (the power needs to be increased, which is not economical), and the maintenance difficulty increases (high-altitude operation equipment is required).
Determination of installation spacing (S): "Brightness uniformity + economy"
The spacing refers to the horizontal distance between two adjacent lamps. It is necessary to ensure that there is no obvious dark area on the road surface (uniformity ≥ 0.4), and avoid waste caused by too small spacing.
1. Core principle: spacing to height ratio (S/H)
Industry-wide "spacing-height ratio" control: the maximum allowable S/H of different lighting types (if exceeded, brightness uniformity decreases):
Narrow lighting: S/H ≤ 2.5 (light is concentrated and needs to be installed densely, such as when H=5 meters, S≤12.5 meters);
Medium lighting: S/H ≤ 3.5 (balanced coverage and uniformity, such as when H=8 meters, S≤28 meters);
Wide lighting: S/H ≤ 4.5 (light diffusion is wide and can be installed sparsely, such as when H=10 meters, S≤45 meters).
2. Adjust based on power and brightness requirements
The higher the light source power (such as 150W LED), the larger the light coverage range, and the spacing can be appropriately widened (10%-20% more than 50W lamps of the same height);
For sections with high requirements for brightness uniformity (such as urban secondary roads), the spacing needs to be reduced (take the lower limit of S/H, such as 3.0 instead of 3.5 for medium light distribution);
For low-brightness demand scenes such as rural branch roads, the spacing can be appropriately enlarged (such as S/H=4.0 for medium light distribution to reduce costs).
3. Verification and optimization: Adjustment in combination with actual scenes
Simulation calculation: Input road width, lamp parameters (power, light distribution), height and spacing through lighting design software (such as DIALux) to simulate the brightness distribution of the road surface. If there is a dark area (brightness is lower than 50% of the standard value), the spacing needs to be reduced or the height needs to be increased.
On-site test: For simple scenes such as rural roads, 1-2 lamps can be installed for testing first:
If the midpoint brightness between the two lamps is significantly lower than the average value (such as lower than 70%), it means that the spacing is too large and needs to be shortened.
If the light is too bright directly below the lamp and too dark at the edge (poor uniformity), it means that the height is insufficient or the light distribution is not matched, and the height needs to be increased or the middle light distribution lamp needs to be replaced.
Cost balance: The smaller the spacing, the better the lighting effect, but the higher the construction cost (the number of lamps increases). Rural roads can give priority to ensuring the spacing of "key areas" (such as village entrances and bends), and the ordinary sections can be appropriately relaxed.
How to ensure the balance between lighting effect and energy consumption in road lighting design?
In road lighting design, the core of the balance between "lighting effect" and "energy consumption" is: under the premise of meeting basic lighting needs (brightness, uniformity, safety), through technology selection, design optimization and intelligent control, minimize ineffective energy consumption and avoid "over-lighting" or "under-lighting".
Specifically, the balance can be achieved from the following 6 dimensions:
Accurately locate "lighting needs": avoid "one size fits all" and reject "over-lighting"
The functions, traffic volume and pedestrian density of different roads vary greatly. It is necessary to first clarify the "necessary lighting standards" rather than blindly pursue high brightness. This is the premise of balance - "low energy consumption" that does not meet the needs is an invalid design, and "high brightness" that exceeds the needs is a waste of energy.
1. Set indicators by road type
Referring to the "Urban Road Lighting Design Standard" (CJJ 45), the core indicators include "average brightness (or illumination), brightness uniformity, and glare limitation", and there are significant differences between different roads:
| Road Type | Average illumination (lx) | Brightness uniformity (minimum) | Glare Limit (Threshold Increment TI) | Core Requirements |
|---|---|---|---|---|
| City Expressway | 20-30 | 0.4 | ≤10% | High-speed driving requires high brightness and low glare |
| Main city roads | 15-20 | 0.4 | ≤15% | Large traffic volume, stable brightness and uniformity are required |
| Urban secondary roads | 10-15 | 0.35 | ≤20% | Considering both vehicles and pedestrians, the brightness can be slightly lower |
| City branch road | 5-10 | 0.3 | ≤25% | Mainly pedestrians and low-speed vehicles, moderate brightness |
| Rural main road | 3-5 | 0.3 | ≤30% | Meet basic recognition requirements (road obstacles, pedestrians) |
| Rural branch road | 1-3 | 0.25 | Relaxation of restrictions | Focus on key areas such as village entrances and bends |
2. "Differential enhancement" in key areas and "moderate simplification" in general areas
Strengthen key areas: At dangerous sections such as intersections, bends, ramps, and school/hospital entrances, the brightness can be increased by 20%-30% (such as the illumination at the main road intersection from 15lx to 18-20lx) to ensure safety;
Weaken general areas: In straight sections and late night periods with extremely low traffic volume, the brightness can be reduced to 50%-70% of the standard value (such as the brightness of the main road after 2 a.m. is reduced from 15lx to 8-10lx), which does not affect basic traffic.
Selection of light sources and lamps: Use "high-efficiency equipment" to reduce "energy consumption per unit brightness"
The ratio of lighting effect (brightness) to energy consumption (power) depends on equipment efficiency - high-efficiency equipment can achieve target brightness with lower power, which is the core technical support for balance.
1. Give priority to high-efficiency LED light sources
Replace traditional light sources: LED light efficiency (80-150lm/W) is much higher than high-pressure sodium lamps (50-80lm/W) and metal halide lamps (60-90lm/W), and energy consumption is reduced by 40%-60% at the same brightness. For example: to achieve 10lx illumination, LED requires 50W, and high-pressure sodium lamps require more than 100W.
Avoid blindly choosing high power: The "power" of LED needs to match road requirements, such as 30-50W for rural branch roads (corresponding to 1-3lx), and there is no need to choose 100W (which will cause overbrightness and energy waste).
2. Match "light distribution and road" to reduce "ineffective light loss"
The light distribution of lamps determines the "effective utilization rate" of light - whether the light is concentrated on the road surface, rather than scattered to the sky or green belt (ineffective energy consumption).
For narrow roads (rural branch roads, 2-3 meters wide), select "narrow light distribution" (light is concentrated on the road surface) to avoid light spillover caused by wide light distribution;
For wide roads (urban main roads, 10-15 meters wide), select / wide light distribution to ensure full road width coverage and avoid increased energy consumption caused by multiple lights superimposed;
It is forbidden to use "floodlights" (non-directional light distribution), whose light utilization rate is less than 50% (a lot of light is wasted in non-road areas).
3. Select "low light decay, long life" lamps
The light decay of lamps will lead to "brightness reduction" - if the light decay is fast (such as 30% decay in 1 year), in order to maintain the effect, it is necessary to replace the lamp in advance or increase the initial power (increase energy consumption).
Choose LED lamps with a 5-year warranty and a 3,000-hour light decay of ≤5% (industry quality standard), and avoid low-priced and low-quality products (the light decay may reach 20% in 1 year);
Select anti-corrosion and heat-dissipating materials (such as aluminum alloy) for the lamp housing to avoid high temperatures, causing a decrease in light efficiency (for every 10°C increase in LED temperature, the light efficiency decreases by 3%-5%).
Optimize "installation and lighting design": use a "reasonable layout" to reduce the number of lamps
Under the same road width, the more reasonable the lamp layout, the fewer lamps are required (directly reducing the total power), while avoiding "local over-brightness/over-darkness".
1. Determine the height and spacing according to the "road width-to-height ratio"
Insufficient height (H): narrow light coverage, need to increase the number of lamps (e.g., a 3-meter-wide rural road, 3-meter-high lamps cover more than 2-meter-high lamps, can reduce 20% of lamps);
Too large spacing (S): obvious dark areas in the middle, need to increase the power of single lamps to compensate (e.g., if the spacing should be 20 meters, if it is extended to 30 meters, the power of single lamps may increase from 50W to 80W, and the total energy consumption will increase).
Principle: Through simulation with software such as DIALux, ensure "the minimum number of lamps" and "the brightness of the entire road section meets the standard" (no dark areas).
2. Single-sided/double-sided lighting can be selected as needed
Narrow roads (≤6 meters): single-sided lighting is sufficient (such as rural main roads), which reduces 50% of lamps compared to double-sided lighting;
Wide roads (＞8 meters): double-sided symmetrical lighting (light superposition covers the entire width), which is more uniform than single-sided lighting (to avoid the edge of one side being too dark and the power needs to be increased).
3. Avoid "cross lighting waste"
Intersections, intersections and other areas are prone to "multi-directional lamp superposition lighting" (such as four-directional street lights illuminating the intersection at the same time), which needs to be optimized:
The intersection lamps are designed separately (using wide-distribution low-power lamps) to replace "extended coverage of peripheral street lights";
The brightness of the superimposed area is simulated by software to avoid the brightness exceeding the standard after superposition (such as the intersection target is 15lx, if it reaches 25lx after superposition, the power of the surrounding lamps needs to be reduced).
Introducing "intelligent control technology": "dynamically adjust" energy consumption according to demand
The "energy waste" of road lighting is mostly due to "fixed brightness throughout the day" - the traffic volume in the middle of the night (2-5 o'clock) is only 5%-10% of that in the daytime, but the brightness is the same as that during peak hours. Intelligent control can achieve "on-demand dimming", reducing energy consumption by 30%-50% without affecting the effect.
1. Time-sharing dimming (basic solution)
Peak hours (18:00-22:00): 100% rated brightness (meet traffic demand);
Off-peak hours (22:00-24:00): 70% brightness (reduced traffic volume, still requires safety identification);
Off-peak hours (24:00-6:00): 40%-50% brightness (only basic lighting is required to avoid total darkness).
Note: Dimming requires "dimmable LED driver" to avoid the decrease in light efficiency caused by ordinary driver dimming.
2. Human-vehicle sensing control (precise solution)
Install microwave radar or infrared sensing device, automatically adjust to 100% brightness when detecting vehicles/pedestrians, and maintain 40% brightness when no detection (suitable for rural roads, branch roads, and other low-traffic scenes);
The sensing range needs to match the road (e.g., 50 meters for rural roads, to avoid triggering frequent dimming due to being too far).
3. Centralized monitoring and fault warning
Remotely monitor the status of lamps through the Internet of Things platform:
Timely discovery of "abnormal lighting" (such as lighting during the day, high-power operation caused by short circuits), and avoid ineffective energy consumption;
Pre-warning of light decay lamps (such as reminding maintenance when the brightness drops to 80% of the initial value), to avoid blindly increasing the overall brightness due to light decay.
Life cycle cost” thinking: refuse to “only look at the initial cost
Some designs choose low-quality lamps (low light efficiency, short life) to reduce initial investment. It seems to save money, but in fact, the long-term energy consumption + replacement cost is higher. It is necessary to balance “initial investment” and “long-term energy consumption”:
| plan | Initial lighting cost (1 km) | Annual energy consumption (kWh) | Total expenditure (cost + energy consumption) over 5 years | 5-year brightness stability |
|---|---|---|---|---|
| Low-quality LED (50W, luminous efficacy 70lm/W) | 5000 yuan (10 lamps) | 50W×10×12h×365=2190 | 5000 + 2190×5×0.6≈11570 rmb | 3 years light decay 30% (lamp needs to be replaced) |
| High quality LED (40W, luminous efficacy 100lm/W) | 8000 yuan (10 lamps） | 40W×10×12h×365=1752 | 8000 + 1752×5×0.6≈13256 rmb | 5-year light decay ≤10% |
| Premium LED + Smart Control | 10,000 yuan (including controller) | 1752×50%=876 | 10000 + 876×5×0.6≈12628 rmb | 5 years of stability |
Strengthen "maintenance management": maintain long-term lighting efficiency
After the lamp has been in operation for 1-2 years, the light effect will decrease due to dust accumulation and aging (such as dust accumulation causing a 15%-20% decrease in light output). If it is not maintained, the power needs to be increased to maintain the effect (increase energy consumption).
1. Clean lamps regularly
Urban roads: clean once every 6 months (reduce dust accumulation and occlusion);
Rural roads: clean once every 12 months (the environment is dusty and needs to be cleaned up).
2. Replace aging parts in time
The life of the driver (the "heart" of the LED) is about 5-8 years. After aging, the efficiency decreases (such as from 90% to 70%), and it needs to be replaced in advance (to avoid the lamp power remaining unchanged, but the light output is reduced);
If the brightness of a single lamp is found to be significantly lower than the surrounding area (serious light decay), replace it in time (to avoid increasing the overall brightness to make up for the dark area).
3. Regular inspection and calibration
Use an illuminance meter to inspect the road brightness every year and compare it with the design value. If the deviation is greater than 20% (too bright/too dark), adjust it by dimming or replacing lamps.
The intelligent control system is calibrated regularly (such as induction sensitivity and dimming curve) to avoid "not bright when it should be bright, not dark when it should be dark".
Summary: The core logic of balance
The "balance between effect and energy consumption" of road lighting is essentially "refusing waste" - no waste of brightness (no excessive lighting), no waste of lamps (reasonable layout), and no waste of electricity (adjustment on demand). The specific path can be summarized as follows:
First clarify the "necessary lighting standards" (determine indicators according to road types);
Use "efficient equipment + reasonable layout" to ensure the "minimum number of lamps + minimum single lamp power";
Use "intelligent control" to achieve "full load during peak demand and reduced load during valley";
Use "maintenance" to maintain long-term efficiency (avoid a hidden increase in energy consumption due to aging).
Through these four steps, energy consumption can be reduced to a minimum while ensuring "road surface brightness meets standards, is uniform without dark areas, and glare is controllable", achieving a win-win situation of "safe lighting" and "green energy saving".
In rural road lighting design, how should different types of lamps be selected?
In the design of rural road lighting, the choice of lighting distribution of lamps needs to be combined with the width of rural roads, road surface materials, the surrounding environment (such as whether crops or houses are blocking), and lighting needs (basic safety lighting is the main focus, avoiding excessive lighting). The core goal is to achieve uniform lighting of the road surface with the lowest energy consumption, while reducing light pollution to surrounding farmland and houses. The following is the logic and specific suggestions for lighting selection in different scenarios:
Clarify the core characteristics of rural roads (the key to affecting the choice of lighting distribution)
The road width is narrow: most rural roads are 3-6 meters (single lane or double lane), and a few main roads can reach 7-9 meters, which is much narrower than urban roads.
The road surface material is diverse: it may be cement, asphalt, or gravel road (low reflectivity, and the lighting needs to be more "close to the ground").
Sensitive to the surrounding environment: There may be farmland, orchards or houses on both sides of the road, and it is necessary to avoid the light of lamps "overflowing" to non-lit areas (such as irradiating crops to affect growth, irradiating houses to affect rest).
Simple lighting requirements: With "clearly seeing the road, pedestrians, and vehicles" as the core, high brightness or decorative lighting is not required for urban roads, and energy consumption is controlled first.
Core indicators for light distribution selection (understand these two parameters first)
Light distribution curve type: the light distribution angle of the lamp, mainly divided into narrow light distribution, medium light distribution, and wide light distribution (divided by horizontal beam angle: narrow light distribution <60°, medium light distribution 60°-90°, wide light distribution >90°).
Cut-off type / non-cut-off type: Cut-off type lamps can control the "overflow rate" of light upward (reduce glare and light pollution), and non-cut-off type light is more dispersed (suitable for open areas without obstructions).
Rural roads give priority to cut-off type or semi-cut-off type (reduce light pollution), and then choose narrow/medium/wide light distribution based on road width.
Lighting selection for different types of rural roads
1. Narrow roads (3-4 meters, single lane, such as alleys in the village and field branches)
Core demand: light is concentrated on the road surface to avoid spreading to the farmland/houses on both sides (narrow roads are prone to "light deviation").
Lighting selection: narrow light distribution (horizontal beam angle 50°-60°) + cut-off type
Reason: The light coverage range of narrow light distribution just matches the 3-4 meter road surface. The beam is concentrated and not divergent, which can reduce the irradiation of the area 1-2 meters away on both sides (such as vegetable fields and courtyard walls on the roadside).
Lamp installation: height 5-6 meters, spacing 15-20 meters (because the light is concentrated, too close spacing will waste energy).
Note: Avoid using wide light distribution (beam angle > 90°), otherwise the light will "sprinkle" to the roadside farmland, which will waste energy and may affect crops.
2. Medium-width roads (5-6 meters, two-lane, such as village main roads and main roads connecting two villages)
Core requirements: The light covers the entire road surface, and the edges on both sides (road shoulders) must also be illuminated (to avoid pedestrians being blocked when walking on the road shoulders).
Light distribution selection: medium light distribution (horizontal beam angle 60°-80°) + half-cut light type
Reason: The beam angle of the medium light distribution just covers 5-6 meters of road surface, and the half-cut light type can control the upward glare (avoid glare to pedestrians) and allow the light to diffuse moderately to the road shoulder (rural pedestrians often walk on the side of the road and need to illuminate the road shoulder).
Supplement: If the road surface is a gravel road (poor reflection), you can choose the "downward projection" type in the medium light distribution (the light is closer to the road surface to reduce air scattering).
Lamp installation: height 6-7 meters, spacing 20-25 meters (the coverage of the medium light distribution is more balanced, and the spacing can be slightly larger than that of narrow roads).
3. Wider roads (7-9 meters, two lanes + sidewalks, such as main roads in towns and roads connecting towns)
Core requirements: Cover the entire road surface and the sidewalks on both sides, while preventing light from irradiating distant farmland or houses (there may be open space on both sides of the road at a certain distance).
Light distribution selection: wide light distribution (horizontal beam angle 90°-120°) + cut-off type
Reason: Wide light distribution can cover 7-9 meters of road surface, and cut-off type controls the "lateral overflow" of light (for example, avoid light from crossing the hedges or walls on both sides of the road and irradiating farmland).
Note: If there are houses on both sides of the road (within 5 meters from the roadside), you need to select **"Bat Wing Light Distribution"** (a special wide light distribution, the light is evenly distributed in the center and both sides of the road, but the edge light decays rapidly to reduce the exposure to houses).
4. Special scenarios: roads with obstructions (such as trees and walls on both sides)
Core requirements: light needs to "avoid obstructions" and fall directly on the road surface (avoid light being blocked by leaves and walls, causing shadows on the road surface).
Light distribution selection: narrow light distribution + small angle downward projection (vertical beam angle <40°)
Reason: The light of narrow light distribution is more "concentrated and downward", and can pass through the gaps of obstructions (such as branches) to illuminate the road surface; if wide light distribution is used, the light is easily reflected or absorbed by the obstruction, resulting in insufficient road brightness.
Example: For a road with tall poplar trees on the roadside, choose a narrow light distribution lamp, and slightly lower the lamp head angle (tilt downward 5°-10°) during installation to reduce the light being blocked by leaves.
Extra attention: avoid two common mistakes
Don't blindly choose "wide light distribution": wide light distribution seems to have a large coverage range, but rural roads are narrow, which can easily cause light to "shine into the fields on the roadside", which wastes electricity and pollutes the environment (some crops are sensitive to continuous light).
Prioritize "directional light distribution LED lamps": Compared with traditional sodium lamps (light divergence), LED lamps can accurately control the light distribution curve, can customize "small angle, low overflow" light distribution according to rural roads, and are more energy-saving (energy consumption can be reduced by more than 30%).
Summary: Tips for choosing light distribution for rural roads
"Narrow roads use narrow distribution, medium roads use medium distribution, and wide roads use wide distribution; narrow distribution is used for obstructions, and interception light is selected near houses, which is energy-saving and protects fields." The core is to let the light "only illuminate the road surface without disturbing the surroundings", and at the same time combine the directional light distribution advantages of LED lamps to achieve the lighting goal of "low cost + low pollution + enough is enough".
How to achieve energy saving with different types of lamps?
The core energy-saving logic of lighting distribution is to let the light "precisely focus on the target lighting area" and reduce ineffective irradiation to unnecessary areas (such as open space outside the road, sky, walls, etc.), so as to avoid "blindly increasing the power of lamps to make up for the waste of light". Different types of lighting distribution achieve energy saving from two levels of "reducing ineffective light loss" and "reducing power demand" by optimizing the angle, direction and concentration of light distribution. The following are the specific principles and energy-saving paths of different types of lighting distribution:
3 core logics of lighting distribution to achieve energy saving
Reduce "ineffective irradiation": light only falls on areas that need to be illuminated (such as roads and work surfaces), and does not spread to surrounding non-target areas (such as farmland, walls, sky), avoiding energy waste caused by "illuminating unnecessary places".
Reduce "glare compensation" energy consumption: unreasonable lighting distribution (such as light scattering, steep angle) is prone to glare (human eyes feel dazzling or blurred), and in order to "let people see clearly", it may be forced to increase the power of lamps (use higher brightness to offset the glare effect); while reasonable lighting distribution can reduce glare without additional power compensation.
Improve "light utilization": light illuminates the target surface (such as the road surface) at the optimal angle, reducing reflection/scattering losses caused by excessive angle deviation (for example, light that is too steep will be absorbed by the road surface material, and light that is too slow will diffuse to both sides). The actual lighting effect is better at the same power, and there is no need to increase the power.
Energy-saving paths for different types of light distribution (combined with scene description)
1. Narrow light distribution (horizontal beam angle <60°): Reduce waste by "precise focusing"
Light distribution characteristics: light is concentrated in a small range (narrow horizontal coverage), extends long longitudinally (along the road direction), and the edge light decays quickly.
Energy-saving principle: In narrow areas (such as 3-4 meters rural alleys and urban sidewalks), narrow light distribution can strictly control the light within the road surface to avoid diffusion to the walls and farmland on both sides. If wide light distribution is used, the light will "overflow" to the roadside. In order to make the road surface reach the target brightness, it may be necessary to increase the power (otherwise the overflowing light will make the road surface actually receive insufficient light); while narrow light distribution does not require additional power, and only low power can make the road surface brightness meet the standard.
Applicable scenarios: narrow roads (single lanes, village alleys), roads close to walls (avoid wasting light on walls).
Energy-saving effect: Compared with the misuse of wide distribution in the same scenario, it can reduce power by 20%-30% (for example, a 15W narrow distribution LED on a narrow road has better road brightness than a 20W wide distribution LED, and there is no overflow).
2. Medium distribution (horizontal beam angle 60°-90°): Avoid repeated lighting by "balanced coverage"
Light distribution characteristics: moderate light coverage, relatively balanced horizontal and vertical distribution, small difference in brightness between the center and edge of the road surface (good uniformity).
Energy-saving principle: In medium-width areas (such as 5-6 meters rural main roads and dual lanes), medium distribution can achieve "single lamp covers a sufficiently wide road surface" and reduce the number of lamps installed (the spacing can be appropriately increased). If narrow light distribution is used, the spacing may need to be reduced (1 lamp per 10 meters becomes 1 lamp per 8 meters), and the total power (single lamp power × quantity) will be higher; medium light distribution reduces the total number of lamps and reduces the total energy consumption through reasonable coverage.
Applicable scenarios: medium-width roads (two-lane roads), open places (such as village squares).
Energy-saving effect: Compared with dense installation of narrow light distribution under the same width, the total energy consumption can be reduced by 15%-25% (for example, a 20W medium light distribution is used for a 6-meter road with a spacing of 20 meters, which is lower than the total power of a 15W narrow light distribution with a spacing of 15 meters).
3. Wide light distribution (horizontal beam angle ＞90°): Reduce the density of lamps by "wide coverage"
Light distribution characteristics: The light has a wide horizontal coverage, which is suitable for large-area lighting, but the edge light is easy to diffuse (need to cooperate with "directional control" to avoid waste).
Energy-saving principle: In wide areas (such as 7-9 meters of main roads in towns and villages, open intersections), wide light distribution can cover a wider road surface with a single lamp, reducing the repeated lighting of lamps on both sides. If medium light distribution is used, it may be necessary to install a row of lamps on both sides of the road (double-row lamps), doubling the total power; while wide light distribution can be arranged in a single row, and the road brightness can be met through horizontal coverage, reducing the number of lamps and total power.
Note: Wide light distribution must be combined with "cut-off design" (control the edge light not to spread outside the road), otherwise the light will shine on farmland and houses, which will waste energy (for example, wide light distribution + non-cut-off type, 30% of the light will overflow to the roadside, and the power needs to be increased to make the road surface meet the standard).
Applicable scenarios: wide roads (two lanes + sidewalks), open intersections without obstructions.
Energy-saving effect: Compared with double-row medium light distribution under the same width, the total energy consumption of single-row wide light distribution (cut-off type) can be reduced by 30%-40%.
4. Cut-off/half-cut-off lighting: Reduce ineffective losses by "controlling upward light"
Light distribution features: Through the design of the lamp shade, limit the upward angle of light (upward light accounts for <10%, half-cut-off type <25%), and reduce the exposure to the sky and trees.
Energy-saving principle: About 20%-40% of the light of non-cut-off lamps (such as traditional bare lamps) will be irradiated upward (towards the sky and tree crowns), and these lights are completely ineffective; while the cut-off type can control the upward light within 10%, allowing more light to irradiate downward to the road surface. Under the same road brightness requirements, the power of the cut-off lamp can be reduced by 20%-30% (no need to "pay" for the waste of upward light).
Applicable scenarios: All areas where light pollution needs to be controlled (there are houses and farmland on both sides of rural roads, and greening on urban roads), especially rural roads (to avoid light shining on farmland and affecting crops, while reducing energy consumption).
Energy-saving effect: Compared with non-cutoff lamps, the power is reduced by more than 20% under the same lighting effect (for example, a 20W cutoff LED on a rural main road has a higher road brightness than a 25W non-cutoff sodium lamp, and there is no upward waste).
5. Batwing lighting (special medium-width lighting): Reduce power demand by "uniform distribution"
Light distribution characteristics: The brightness difference between the center and edge of the road is small (high uniformity), and the lateral distribution is "slightly lower in the middle and slightly higher on both sides" (similar to the shape of a bat wing), reducing the problem of too bright in the center and too dark at the edge.
Energy-saving principle: Ordinary lighting may appear "too bright directly below the lamp and too dark at the edge". In order to make the edge meet the standard, the power may be forced to increase (causing the center brightness to far exceed the demand); while the batwing lighting has high uniformity, and there is no need to increase the power to compensate for the dark area at the edge. The target brightness of the entire road can be achieved with lower power.
Applicable scenarios: roads with high uniformity requirements (such as rural main roads and roads connecting towns, to avoid visual fatigue of pedestrians/vehicles due to uneven brightness).
Energy-saving effect: Compared with ordinary medium light distribution, the power can be reduced by 15%-20% under the same uniformity (for example, if the target brightness is 5lux, 18W is enough for bat-wing light distribution, and 22W is required for ordinary medium light distribution).
Key principles of light distribution energy saving (avoid the misunderstanding of "saving energy for energy saving"
"Light distribution on demand" rather than "blindly selecting narrow/wide": narrow light distribution used on wide roads will cause dark edges (need to add lights), and wide light distribution used on narrow roads will cause light overflow (need to reduce power but insufficient brightness), which is not energy-saving. Light distribution must be selected according to the width and shape of the lighting area (such as narrow light distribution for 3-meter roads and medium light distribution for 6-meter roads).
Prioritize "cut-off light type + directional light distribution": Regardless of narrow/medium/wide light distribution, the cut-off light design can reduce 80% of invalid upward light, which is the core of energy saving for rural roads (rural areas are sensitive to light pollution and have low energy consumption budgets).
Combined with road material adjustment: gravel roads (low reflectivity) need to have a light distribution that is closer to the ground (slightly narrower beam angle to reduce scattering) to prevent excessive light absorption by the road surface; cement/asphalt roads (high reflectivity) can appropriately relax the light distribution and use reflection to improve utilization.
Summary: The core of light distribution energy saving is "let the light do no useless work"
Different light distributions reduce invalid irradiation (power waste caused by overflow, upward irradiation, and uneven brightness) by precisely controlling the irradiation range (lateral width), direction (up and down angles) and uniformity of light. For rural roads, the "cut-off light type + narrow/medium light distribution as needed" is the most energy-saving combination - the cut-off light type reduces the waste of upward projection, and the narrow/medium light distribution avoids diffusion to farmland. The combination of the two can meet the basic lighting needs while keeping energy consumption at the lowest level (saving more than 30% energy compared to unreasonable light distribution solutions).
