How can LED streetlights improve nighttime driving safety?

According to data from the Traffic Management Bureau, nighttime driving time accounts for only about 25% of the total daily driving time, but nighttime traffic accidents account for over 40%, with insufficient or inappropriate lighting being a significant contributing factor. Compared to traditional high-pressure sodium lamps, LED streetlights, with their advantages of strong controllability and stable light color, have become a core infrastructure for improving nighttime driving safety. However, not all LED streetlights can effectively guarantee driving safety; the key lies in whether they meet stringent lighting standards, employ scientific light distribution design, and possess intelligent adjustment capabilities adapted to driving scenarios. This article will comprehensively analyze the technical key points and practical solutions for ensuring nighttime driving safety with LED streetlights.

I. Basic Guarantee: Compliance with National Standards for Lighting Grades

The primary prerequisite for safe nighttime driving is that road lighting meets the specified brightness and uniformity standards. Different road types have significantly different requirements for lighting grades. The "GB 50034-2024 Standard for Lighting Design of Buildings," implemented in 2025, clearly classifies urban road lighting grades. The selection and installation of LED streetlights must strictly adhere to this standard to avoid either "overly bright and wasteful" or "overly dim and dangerous" lighting.

1. Core Indicators: Luminosity, Uniformity, and Glare Limitation

The key lighting indicators for different road grades are as follows:

• - Highways/Urban Expressways: Average road surface luminosity ≥ 2.0 cd/m², luminosity uniformity (minimum luminosity/average luminosity) ≥ 0.4, longitudinal uniformity ≥ 0.7, glare limit threshold increment (TI) ≤ 10%;
• - Urban Arterial Roads: Average luminosity ≥ 1.5 cd/m², luminosity uniformity ≥ 0.35, longitudinal uniformity ≥ 0.6, TI ≤ 15%;
• - Secondary Arterial Roads and Local Roads: Average luminosity ≥ 1.0 cd/m² and 0.5 cd/m² respectively, luminosity uniformity ≥ 0.3, TI ≤ 20%.

Among these, luminosity uniformity is crucial for ensuring driving safety—if the road surface brightness fluctuates, the driver's pupils need to adjust frequently, easily leading to visual fatigue and increasing reaction time by 20%-30%. Glare control is directly related to the visual safety of oncoming drivers. An excessively high TI value can cause temporary "blindness" for the driver, leading to rear-end collisions or other accidents.

2. Light Color Selection: Balancing Clarity and Comfort

The color temperature and color rendering index (CRI) of LED streetlights have a profound impact on nighttime driving safety. Regarding color temperature, a neutral white light of 3500K-5000K is the optimal choice: warm white light below 3500K has weaker penetration through fog and rain and can easily cause driver drowsiness; cool white light above 5000K increases the risk of glare and reduces visual comfort. A CRI (Ra) of ≥70 ensures that drivers can accurately identify road markings, traffic signals, and the color of pedestrian clothing—for example, in a lighting environment with Ra=80, the distance at which a driver can identify a red obstacle increases by 15-20 meters compared to Ra=60, allowing more time for emergency braking.

II. Core Technology: Scientific Light Distribution Design Eliminates Illumination "Blind Spots"

Even if LED streetlights meet brightness standards, improper light distribution design can still result in overlapping light spots or "blind spots" on the road surface, posing a safety hazard to drivers. By 2025, mainstream light distribution design has shifted from "floodlighting" to "precision light control," achieving uniform road surface illumination and glare-free operation through optical simulation and scene adaptation.

1. Beam Distribution Curve: Customized Based on Road Type

The beam distribution curve of an LED streetlight determines the direction of light energy distribution and needs to be customized based on parameters such as road width and pole spacing:

• - Narrow Beam Distribution (Type I/II): Suitable for side roads with a width ≤ 12 meters. Light energy is concentrated within a 30° range on both sides of the pole, avoiding light waste.
• - Medium Beam Distribution (Type III): Suitable for secondary roads 12-18 meters wide. Beam distribution angle is 60°-90°, balancing illumination width and uniformity.
• - Wide Beam Distribution (Type IV/V): Suitable for main roads and expressways ≥ 18 meters wide. Beam distribution angle is ≥ 120°. Combined with a pole spacing of 30-50 meters, it achieves complete road coverage without blind spots.

For example, a city's main road used Type V wide beam distribution LED streetlights. The pole height was 12 meters and the spacing was 40 meters. Actual measurements showed an average road surface brightness of 1.8 cd/m² and a uniformity of 0.42, fully meeting national standards. The nighttime traffic accident rate decreased by 28% year-on-year. 2. Anti-glare Design: Optimized Optical Lenses and Installation Angles

Glare primarily originates from direct light from LED light sources entering the driver's line of sight. This can be addressed through a dual approach: "optical lenses + installation angle adjustment." The optical lenses employ a batwing or cut-off design to keep light below the road surface, reducing upward and lateral light leakage. During installation, the streetlight elevation angle should be ≤5°, and the angle between the light source center and the driver's line of sight should be ≥15° to avoid direct glare. Furthermore, some high-end products utilize microstructured optical films to reduce glare values through light scattering, achieving a TI (glare intensity) of less than 8%, far exceeding the national standard limit.

III. Intelligent Upgrade: Scene-Based Adaptive Lighting System

Nighttime driving scenarios are complex and varied (e.g., rain, fog, sudden increases in traffic volume), making it difficult for fixed-brightness LED streetlights to handle all situations. By 2025, intelligent LED streetlights will utilize "sensors + AI algorithms" to dynamically adjust lighting parameters, further enhancing driving safety.

1. Environmentally Adaptive Dimming: Coping with Severe Weather

LED streetlights integrating temperature, humidity, and visibility sensors can automatically adjust light output according to weather changes. For example, in foggy weather, when light penetration is reduced, the system can increase brightness by 20%-30% while switching to warm white light with a color temperature of 3000K-3500K to enhance light penetration. In rainy weather, it appropriately increases brightness uniformity to avoid the "mirror effect" caused by road surface glare, helping drivers clearly see road markings.

2. Traffic Flow Linked Control: Precise Lighting in Key Areas

By monitoring traffic flow through video surveillance or microwave radar sensors, when an approaching vehicle is detected, the streetlight can increase its brightness from the base brightness (e.g., 50%) to 100% within 0.3 seconds, returning to the base brightness after the vehicle leaves. This "on-demand lighting" mode not only saves energy but also allows drivers to adapt to brightness changes in advance when entering the illuminated area, avoiding the "black hole effect"—a brief visual blind spot when moving from a bright area to a dark area. After piloting this system at a highway service area, nighttime vehicle collision accidents decreased by 35%.

IV. Case Study: Nighttime Driving Safety Lighting Upgrade Project in a New Urban Area

A new urban area upgraded the lighting on three main roads with high rates of nighttime traffic accidents, adopting a "Type V wide-beam LED streetlight + intelligent adaptive system" solution: the streetlights have an initial luminous efficacy of 160 lm/W, a color rendering index of 85, a beam angle of 130°, and an installation elevation angle of 3°; simultaneously, visibility sensors and microwave radar are integrated to achieve intelligent control for increased brightness in foggy weather and increased brightness when vehicles approach. Actual measurement data after the upgrade showed: the average road surface brightness increased to 2.1 cd/m², uniformity was 0.45, glare TI value was 8.5%, the nighttime traffic accident rate decreased by 32% year-on-year, and driver visual fatigue complaints decreased by 40%.

Conclusion: Safe lighting requires a three-pronged approach of "standards + technology + intelligence"

Improving nighttime driving safety with LED streetlights is not simply about "lighting up," but about achieving "precise lighting, intelligent lighting, and safe lighting." When planning and procuring lighting, municipal departments must prioritize products with scientific light distribution and anti-glare design, based on national lighting standards, and deploy intelligent adaptive systems in accordance with regional traffic characteristics. Only by deeply integrating "standards and specifications, technological innovation, and scenario adaptation" can LED streetlights truly become "safety guardians" for nighttime driving, laying a solid foundation for urban traffic safety.