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Highway Lighting Guide
Lighting Up the Road to Somewhere
Highway lighting plays an important role in ensuring that the roadways are safe for drivers by ensuring that the streets are visible, even at night. Highway lighting, although similar to street lighting, serves a much more vast purpose.
Highway lights allow drivers to safely traverse uninhabited stretches of road without danger. They illuminate other vehicles, but also barriers, bridges, signs, and ditches to help reduce car accidents.
Adequate highway lighting should make drivers feel safer and more comfortable and can decrease the likelihood of roadway incidents by up to 30%.
Highway Lighting Checklist
When installing good, high-quality lighting, you can expect it to do the following things.
Extend the range of visibility beyond the limits of vehicle headlights both sideways and lengthwise.
Enhance road visibility as well as the visibility of objects and features on the road or near it.
Outline the road ahead and enhance the range of vision of the road and its surrounding area.
Reduce the angst of everyone using the road.
Highway Lighting Visibility Requirements
Although illuminating the highway accomplishes all the tasks above, the only thing it physically does is improve visibility. With this information, installing the brightest light you can find only makes sense. But there are several nuances to consider, as with any type of lighting. As the light levels reduce, the ability to detect information and visibility becomes drastically impaired or completely nonexistent.
Alternatively, as light levels rise, vision improves, and detecting information becomes much easier.
Again, this information may lead you to believe that choosing the brightest light possible is best, but there are other factors in play here. And one of those factors is contrast.
The contrast between two objects lies in the different levels of brightness between the background and the object. As the level of contrast increases, it becomes easier and easier to differentiate the subject from the background. When driving, people usually perceive objects in forms – a dark space against a bright background. Nevertheless, that bright background might result in glare which can reduce the level of contrast as well as the driver’s ability to see details.
The best way to balance the need for a bright light and no glare is to be mindful of the light’s angle, and the quality of the light. LED Highway lighting is your best choice, and the easiest way to avoid a blinding glare. And at the same time, picking the right light will help reduce light pollution.
Most Common Types of Highway Lights
The majority of LED highway lights have a lens on the LED panel which casts light rectangularly, directing a great part of the light to the side of the street.
LEDs are the most popular choice for highway lighting because of their low operating and maintenance costs.
Metal halide fixtures generate light via a mixture of metallic vapors. These lights have a high initial lumen output, but this quickly degrades with regular use.
In addition to this, metal halide lights consume energy and, as a result, have extremely high electrical costs.
Despite this, metal halides might be the most common type of highway light.
High-pressure sodium lights use sodium vapor to help produce lumens. Like fluorescents, HPS fixtures also contain small amounts of mercury, that require special disposal procedures.
These lights are extremely bright but lose lumens quickly and produce a warm-colored light with a low CRI.
HID Highway Lights
These fixtures produce light by exciting gases or metal vapors, located in a lamp or tube. They are generally considered too fragile to be used for highway lighting but are occasionally employed for their high-lumen output.
Unfortunately, this lumen output decreases very rapidly, making them a poor choice for almost any lighting application.
So, what’s your best option?
It’s not hard to see, LEDs are the best choice for highway lighting. But in the interest of being succinct, LED lights are the most energy-efficient bulbs and have the longest lifespan of any light. The savings on energy costs are an obvious benefit, but the reduction in maintenance costs often flies under the radar. When you must employ an entire crew and use heavy machinery to replace light bulbs, a long lifespan and maintenance-free shine can be even more financially rewarding than the electrical savings that LEDs provide.
Highway Lighting Fixtures
Based on the needed lighting level, conventional lighting can have different mounting heights. The conventional FDOT mounting heights are 40, 45, and 50 feet. For standard mountings, there is one luminaire per pole. If it is medium mounted, it can have two luminaries per pole. Take a look at the table below outlining the FDOT prerequisites for levels of illumination and ratios of uniformity for standard lighting.
Illumination Levels, Average Initial Foot Candles
|Interstate Expressway, Freeways and Major Arterials||1.5||<= 4.1||<= 10.1|
|All other roadways||1||<= 4.1||<= 10.1|
|Pedestrian Walkways and Bike Lanes||2.5||<= 4.1||<= 10.1|
Interchanges: High Mast Lighting
High Mast Lighting involves a mounting height of 80 feet or more. The conventional mounting height is 120 feet. There can be numerous luminaries per pole.
The number of luminaries is based on the needed light level. The biggest number of luminaries per pole is 12 to 16 lights. With the help of cables, the luminaries are connected to a ring and to a winch at the base of the pole.
The luminaries and the ring are lowered to the ground with the help of the winch for maintenance. For this, either a previously installed electric motor is used to lower the ring, or a heavy-duty drill motor is attached to the pole to operate the winch.
Take a look at the table below which describes the FDOT prerequisites for levels of illumination and uniformity.
Illumination Levels, Average Initial Foot Candles
|Interstate Expressway, Freeways and Major Arterials||0.8 – 1.0||<= 3.1||<= 10.1|
|All other roadways||0.8 – 1.0||<= 3.1||<= 10.1|
Overhead sign structures need overhead sign lighting that will make the messages portrayed visible during both day and night. They are a crucial element of highway lighting since they relate important information to drivers 24/7.
In the past couple of years, sign designers have created a unique sheeting on the sign which illuminates the sign with the help of vehicle headlights. These signs are more expensive than standard signs. Nevertheless, this kind of sheeting minimizes the expenditure for sign lighting as well as the associated conduit and pull boxes.
Nowadays, most major intersections have various wide overpasses. In those areas, proper lighting throughout the day and night is a must for the roads under the overpasses.
Underdeck lighting involves mounting either a pier cap or pendant hung fixtures under the structure of the bridge. Pier cap fixtures must be installed when bridge piers are less than 15 feet from the edge of the travel lane.
The pendant hung lights should be mounted to the bottom part of the bridge deck and should be suspended where 50% of the lamp is below the bridge beam.
No fixture or light should be attached to the bridge girders. The underdeck lighting levels should be equal to the adjacent road lighting.
Highway Lighting and LED
Highway lighting is absolutely essential. Not only does it keep the roadways safe and visible at night, but it also provides drivers with a way to read signs and makes them feel more comfortable.
Adequate highway lighting reduces the number of car accidents and makes the roads a better place to drive.
But, as you know by now, not all lights are created equally. LED lighting is perfect for highway lights because of its low maintenance requirements, extra-long lifespan, and natural durability.
LEDs lights may cost slightly more at the onset of installation, but that money will be made back quickly with lower electrical bills and non-existent operating costs.
Sometimes deciding between types of lighting is difficult, but in this case it’s pretty cut and dry. LED is not only the best choice for highway lighting, but also the perfect one.
About the Author
Neil Peterson is Chief Operating Officer at LED Lighting Supply. He has been active in the LED industry for over 10 years and is responsible for product planning and management as well as revenue and operations at LED Lighting Supply. Much of Neil’s time is focused on customer engagement for large commercial and industrial lighting requirements. When not working, he enjoys family time, camping, fishing, and sports..