Introduction

Street light LED should be installed alongside or in the middle of the road, or suspended from wires above the road to provide lighting. At the same time, at intersections and roundabouts, street lighting is also required because the road conditions in these areas are more complicated.

On roads or highways with lighting needs, street lighting can provide a safer, more comfortable and more convenient environment for vehicles and pedestrians to move at night. In addition, street light LED should be effectively managed to facilitate future maintenance, replacement or renewal to provide long-term lighting services for traffic flow and pedestrians. Below we list several important roles of street lighting.

• Reduce the risk of accidents at night
• Fight against crime
• Assist in the protection of buildings/property
• Create a safe and pleasant living environment
• Stop vandalism

Importance of street lighting design

In the previous section we talked about the importance of street lighting. So how can we have the right street lighting effect. We think street lighting simulation is essential. Street lighting design involves the selection and installation of lighting equipment(street light LED) to maximize visibility and increase safety while meeting the needs of users with minimal energy consumption. A reasonable street lighting design ZGSM believes should include the following two points: 1. The choice of lighting standards, here mainly refers to the road illumination, brightness, glare, uniformity and so on. 2. Implementation of road lighting simulation to confirm suitable lamps, pole arrangement, pole height, pole spacing, pole arm, tilt angle, setback, etc.

If you don’t know about point 1, we recommend checking our another blog regarding street lighting design. For the latter, ZGSM believes that the choice and setting of street light LED and street light poles have a significant impact on the appearance of road schemes/ city construction, and we should plan street lighting as a whole at the initial stage. In addition, in historic towns and protected areas, particular attention should be paid to the aesthetic qualities of street lighting design and installation, while equal care should be taken to avoid light pollution, especially in rural areas.

Luminaire arrangement of street lighting

There are four basic types of street lighting arrangements for motorways or highways, which we describe as below.

Single sided arrangement(arrangement at only one side, upper side or bottom side）

Single sided arrangement, that is, all lamps are located on one side of the road, and should be used when the width of the road is less than or equal to the installation height. This type of lighting arrangement is usually suitable for narrower roads. Usually the installation height is lower at about 6 meters (20 inches). In addition, as the lens design of street lamps becomes more and more sophisticated, this type of lighting can sometimes be used to illuminate wider roads.

Staggered arrangement(two-sided arrangement offset)

Staggered arrangement, when the road width is equal to 1 to 1.5 times of the installation height, the lamps are alternately placed on both sides of the road in a “zig-zag” or staggered style. This type of lighting arrangement is usually suitable for medium sized roads. Practice has proved that the lighting effect (uniformity) of staggered street lighting arrangement is often improved without increasing the height of the pole.

Opposite arrangement(two-sided arrangement)

Opposite arrangement, the lamps are placed opposite to each other along the front of the road. When the width of the road is greater than 1.5 times of the installation height, it is more suitable to go with this arrangement. Opposite arrangement is usually suitable for medium to wide roads. This kind of lighting arrangement is very common on main roads, mainly because of convenient construction and excellent lighting effect.

Twin central arrangement(median arrangement)

Twin central arrangement, the lamps are installed on the T-shaped mast in the middle of the central island of the road, when the road width is less than or equal to the installation height, the installation height of the lamps should be used. This type of lighting arrangement is usually installed on taller poles and large roads. This type of light distribution method often requires a wide isolation island on the road, which facilitates the installation of light poles and distribution boxes.

Street light height

Street light LED are installed on high lamp post. And the roadway light poles are generally in 4 meters(13 feet), 6 meters(20 feet), 8 meters(26-27 feet), 10 meters(33 feet), 12 meters(40 feet). Below we list the different The height of the light pole is generally the application place.

• 10-20 feet, suitable for residential areas, park roads, country roads
• 20-27 feet, suitable for most urban roads, commuter roads between urban and rural areas
• 27-33 feet, suitable for urban main roads, expressways and highways, etc.
• 33-40 feet, suitable for wider roads with high traffic flow, road intersections
• > 40ft, high mast light pole for installation in large areas such as airports, shipyards, large industrial areas, sports fields and road intersections.

Proper Placement of Pole

Pole distance from the roadway(Setback)

This is the distance from the light pole to the road. Because the street lights are generally set on the outside of the street curb, the light poles have a certain horizontal distance from the motor vehicle lane or the non-motor vehicle lane. This horizontal distance is also usually called setback.

For most arrangements, setback will choose 1 foot to 2 feet. Light poles that are too close are not suitable for installation and are easily affected by accidental traffic accidents, which in turn can cause more accidents. Too far away, and the lighting effect (light level and uniformity) is reduced, and even further distances from the fixture create shadows at low light levels. For the twin central arrangement, the setback is half the width of the isolation island.

Pole Boom(Arm) Length

The use of arms brings the light source closer to the road while keeping the poles positioned away from the edge of the road. Depending on the application, the arm may be a single and/or double arm or a davit arm on top of the pole.

There are several different arm lengths and styles of arms used. Single arms, these arms are typically available in 1.5m, 2m and 2.5m lengths. Double arms, these arms face 180° apart and are used to illuminate the opposite lane of a two-way lane.

Overhang

Overhang is the horizontal distance from the center of the light fixture mounted on the bracket (poles) to the edge of the driveway. In general, the overhang should not exceed a quarter of the installation height to avoid reduced visibility from shoulders, obstacles and sidewalks. In addition, due to the influence of the trees on the road, the overhang will be increased to reduce the influence of the trees on the road. Also set up additional street lights to illuminate the sidewalk.

Boom Tilt Angle (Boom Angle)

Boom tilt angle is the angle between the luminous surface and the horizontal plane (the surface parallel to the ground). Nornally the larger the tilt angle, the higher the uniformity in general. In the past, there would be a tilt angle during actual road installation, which was relatively large and had corresponding problems. Uncomfortable glare is increasing as bright light enters the driver’s eyes. Therefore, ZGSM recommends that the tilt angle should be kept below 15 degrees. As more and more project parties require zero uplight, this angle is usually 0. Thanks to the improvement of the lighting distribution, ZGSM street lights are often installed on light poles with a 0 tilt angle. Even if the tilt angle is 15 degrees, by adjusting the fitter, we can achieve 0 degrees to reduce the impact on the natural environment.

Pole to Pole distance(Spacing)

Spacing is the distance between two consecutive luminaires along the centerline of the road. Usually spacing equal to 3 to 4.5 times is suitable for many road lighting projects. The smaller the pole distance, the better uniformity can usually be obtained, but we will need more light poles, which is not conducive to controlling the cost of the project. The longer the poles distance, the poorer the uniformity, because the illumination and brightness are often lower in places farther away from the lamps, which can easily cause discontinuity in lighting and affect traffic safety. Taking an 8-meter light pole as an example, we generally recommend that the distance between the light poles is about 30 meters (single side lighting). If it is installed on the opposite side or staggered, the distance can be increased to 35 meters or more. Below we have attached a pictures shows the setback, boom length, overhang, boom angle, spacing which gives a profound image of these parameters.

ZGSM street light LED

Summary

Through this article, we hope that you have a certain understanding of street light LED and road lighting simulation(street lighting design). This article focuses on the street light arrangement and the selection of pole heights in road lighting simulation. At the same time, other parameters of the light pole (light pole arm, tilt angle) and the arrangement of the light pole (setback and light pole spacing) are expounded. All these parameters mentioned above are very important in lighting simulation. In most cases, the parameters and arrangement of the light poles have been determined, and we need to confirm the selection of street light LED (including style, wattage and lens) by inputting these parameters in Dialux software. It is also necessary to confirm the arrangement of the light poles (spacing) if it’s not specified. Generally speaking, the larger the spacing, the better. At this time, the determining factor is the design of street light(lighting distribution) itself. Hope you all keep all these concepts in mind, we believe it will be a great help in your future operational lighting simulations and project implementations.

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