The primary purpose of street lighting is to provide drivers with appropriate lighting levels for safe driving and pedestrians with safe walking.
In cities, street lighting also plays an additional role in creating a more attractive and safer environment. The ability of urban street lighting to illuminate objects is affected by light quality and other physical factors, such as traffic flow and road surface. A good street lighting system ensures visual detection of objects at greater distances.
In response to the increasing number of outdoor LED lighting projects, Haopai, a professional LED street light developer, has launched a street light design program to provide customers with more comprehensive technical support.
Lighting effects and overall quantity can better communicate with end customers and more accurately calculate project costs. We also provide customers with detailed street light data to meet their diverse lighting needs.
This article will describe the various lighting factors that should be considered when designing an effective lighting system.
What are the key factors to consider when selecting a die-cast aluminum LED street light?
Average Road Luminance Lav (unit: Cd/m)
Road luminance is a measure of road visibility. It is the most important factor affecting obstacle visibility, based on illuminating the roadway so that the outlines of obstacles can be clearly seen.
Brightness (road brightness) depends on the light distribution of the luminaire, its lumen output, the streetlight mounting design, and the reflective properties of the road surface. Higher brightness levels provide better lighting. According to lighting level standards, Lav ranges from 0.3 to 2.0 Cd/m².
Uniformity
Uniformity is a measure of the uniformity of road light distribution and can be expressed as overall uniformity (U0) and longitudinal uniformity (UI).
Die-cast aluminum LED street lights must determine the allowable difference between the minimum and average brightness on the roadway, known as total brightness uniformity. This is defined as the ratio of the minimum to average brightness on the roadway.
Good total brightness uniformity ensures that all points and objects on the roadway are adequately illuminated for drivers to see clearly. An acceptable Uo value in the roadway lighting industry is 0.40.
Glare
Glare is the sensation of glare caused when light brightness exceeds the human eye's adaptation range. Glare can cause discomfort and reduce road visibility. Its measurement unit is the threshold increment (TI), which is the percentage increase in luminance required to compensate for glare (i.e., to make the road visible without glare).
Average Road Illuminance, Minimum Road Illuminance, and Vertical Illuminance
Lighting requirements for motorways are generally based on luminance, while sidewalk lighting requirements are primarily based on road illuminance.
This depends on the light distribution. The uniformity of streetlight illumination is related to the luminaire's power, lumen output, and installation design, but is less dependent on the reflective properties of the road.
For sidewalk lighting, illuminance uniformity (UE) (Lmin/Lav) is also important. This is the ratio of the minimum illuminance to the average illuminance on the road. To ensure uniformity, the actual average illuminance must not exceed 1.5 times the nominal value for the grade.
Color Rendering Index (CRI) measures the ability of an artificial light source to display or reproduce the color of the road or roadway objects relative to natural light sources. The CRI for natural light (sunlight) is 100. A higher CRI indicates better visibility. It is recommended that the color rendering index of all types of road lighting should be ≥70.