How to Design Street Lighting
Pole and Street lighting design is essential as it allows people to safely continue their travels uninterrupted. Whether the light is for footpaths, roads or sportsfields; it is important to understand the intention of pole/street lighting:
- They can reduce the risk of night-time accidents
- Discouraging destruction of property and vandalism
- Discouraging many crimes from being committed
- They create a safe and secure environment for habitation
- The lighting provides a specific level of brightness and uniformity to perform a specific task
The Basic Features of Street Light Luminaires
The basic features of a pole/street luminaire:
- Roadway luminaires are mounted in a horizontal fashion in order to provide fixed vertical aiming.
- Roadway lighting luminaires have a specific amount of intensity distributions which are desired to light the long narrow horizontal stripes on one side of the luminaire, while they limit the intensities on the opposite side of the luminaire.
- The intensity distributions both up and down the narrow strip are generally equal to one another.
- Any fixed aimed luminaire that does not have this specific type of intensity distribution is called an area luminaire.
Main Objectives of Street Lighting Design Scheme
The are three main objectives of street lighting design schemes and all are equally important.
- The perfect visual sensation for safety reasons
- A well lit environment that is safe for quick movement of all of the vehicles
- Providing a clear view of objects so all travelers feel comfortable and safe at the speed of travel
- Creating the correct environment (brightness, uniformity, glare control) to carry out a specific task e.g. playing competitive football or picking/packing goods
Main Factors in the Street Lighting Design Scheme
1. Proper Luminance Lighting Levels for the Specific Area and its Purposes.
Luminance always influences the contrast sensitivity of the surrounding obstructions with a respect to the background areas. If a street is brighter, the darker surroundings will cause the driver to adapt, unless the driver is unable to make out the objects in the surrounding areas. As per CIE, 5 miles away from the road on both sides will be lit by a Illuminance level that is at least 50% of that on the road.
2. Luminance Uniformity is a MUST
In order to provide a visual comfort level for the viewer’s eyes, enough luminous uniformity is necessary. Luminous uniformity means that the ratio between the minimum luminance level to the average luminance level by using the proper equation.Â
It is termed as longitudinal uniformity ratio because it is measured along the line passing through a viewer’s position in the middle of the traffic that is facing the traffic flow.
3. The Degree of Glare Limitation Must Always be Taken into Design Schemes
A glare means there is going to be a visual discomfort because of the high luminance. There are two different kinds of glares caused by streetlight luminaires. The first type is a disability glare and the second type are a discomfort glare.
A disability glare is not a very strong factor, rather discomfort glare is a common factor due to unplanned street lighting schemes. Which is why the degree of the glare is so important. Eliminating unnecessary glares can save lives and eliminate accidents due to being unable to see properly.
4. Lamp Spectra for Visual Sharpness Depends on the Proper Luminaries
It is extremely important to make an object as per its size and dimension in order for drivers to avoid accidents.
5. The Effectiveness of Visual Guidance is an Essential Key Factor
The effectiveness of visual guidance helps a viewer to properly guess how far another object is from their current position, as well as, being able to guess the range of upcoming objects.
Types of Road to Implement Various Street Lighting Design Schemes
The type of road that is being lit for travel will require different lighting. This is because the size of the roads varies, the amount of traffic, and the surrounding area all vary. According to each situation there are aspects that must be accounted for before designing and installing lights. As per CIE there are 12 roads that are broadly classified into five different types.
Street Lighting Design: Type A
- Heavy and high-speed traffic
- The roads that are separated with the separators or mediums
- No crossing is allowed
- Controlled access
- Example: Expressways
Street Lighting Design: Type B
- Heavy and high-speed traffic
- Separate roads for slower moving traffic and/or pedestrians
- Example: Trunk roads
Street Lighting Design: Type C
- Heavy traffic mixed with moderate speed traffic
- Rural and urban roads
- Examples: Ring Road or Radial Road
Street Lighting Design: Type D
- Slow traffic and pedestrians’ use
- Road in the city or a shopping centre
- Example: Shopping streets
Street Lighting Design: Type E
- Mixed Traffic with limited speeds
- Connector road between residential areas
- Example: Local streets
This guide provides a more in-depth look at designing lighting for streets. Keep in mind that all countries and states will have their own codes that must be followed but the equations for calculation are all relatively similar.
Designing street lighting isn’t easy and there are a lot of codes to follow but the lighting is essential for night time traveling. The information shared here is just the beginning to designing street lighting. As it has been mentioned, there are numerous equations and formulas required to properly and safely design streetlights.
Once you know the equations and codes to follow it you’ll have everything you need to begin your lighting design. Don’t forget to look into the codes for the area before starting any formulation.
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