Lighting on highways supports the safety, efficiency, and functionality of our roadways. For transportation leaders and city planners, dependable lighting is key to creating accessible infrastructure. A well-designed highway lighting system reduces accidents, aids traffic flow, and improves the experience for travelers. This planner’s guide will walk you through the basics of highway lighting design by exploring lighting principles and the latest energy-efficient technologies.
Understanding the Principles of Highway Lighting
Highway lighting design starts with understanding three essential principles that determine how well and efficiently a roadway can be illuminated. These principles include illuminance, luminance, and uniformity.
Illuminance
Illuminance is a measure of the amount of light that falls onto a specific surface area. It’s measured in lux in the metric system and foot candles in the Imperial system. The intensity and installation height of the light source both have an impact on illuminance. For highways, adequate illuminance ensures that the roadway is visible to drivers and pedestrians, even in dim or dark conditions.
Luminance
Illuminance is a measure of light falling on a surface. Luminance, on the other hand, measures what a driver actually perceives. We measure this lighting principle in candelas, and it has more to do with how the light interacts with a surface rather than the light source itself. This is vital for seeing lane dividers, roadway markings, and other vehicles on highways.
Uniformity
Uniformity is a measure of how evenly light distributes across a road surface. Uneven lighting can create dark spots, which may pose safety risks. Overly lit areas can cause glare. Striking a balance ensures drivers can adjust to lighting conditions as they navigate the roadway. By combining these three principles in the planning stage, planners can design a seamless lighting experience that minimizes risks and enhances usability.
Key Factors Influencing Highway Lighting Design
Every highway lighting project presents a unique combination of challenges and design priorities. Understanding key factors, such as roadway geometry, speed limits, and traffic volume, can help you tailor solutions that meet the needs of your project.
Roadway Geometry
The shape and layout of the road, including curves, inclines, and intersections, play a big role in determining how you should position lights. For example, curves may require additional lighting to guide drivers, while intersections might call for higher illuminance levels to improve visibility.
Speed Limits
High speed limits on freeways typically necessitate brighter and more uniform lighting to accommodate the reduced reaction times of drivers traveling at fast speeds. Conversely, slower speed zones, such as divided urban highways, can have fewer fixtures with more focused lighting.
Traffic Volume
Heavily trafficked highways demand lighting systems that can endure all types of weather while remaining effective. High volumes of vehicles also require uniform lighting to prevent blind spots and minimize confusion during heavy traffic conditions.
Types of Highway Lighting Systems
Different sections of a highway call for varied lighting approaches. Here are four types of highway lighting systems and where they shine.
1. Conventional Lighting
This is the most common system, using spaced poles (typically 30–40 feet tall) with standard street light fixtures. Conventional lighting works well for simpler roadway segments, such as straight highways or areas with consistent traffic.
2. High-Mast Lighting
High-mast lighting uses taller poles (100–150 feet) to cover a wide area. These are commonplace at interchanges, roundabouts, and large toll plazas where broad, consistent lighting is necessary. These systems reduce the number of poles required while still delivering high illuminance across vast areas.
3. Underpass and Tunnel Lighting
Underpass and tunnel lighting boost safety and visibility in areas with insufficient natural light. These systems use specialized fixtures and color temperatures that reduce glare while maintaining consistent brightness. Lighting in tunnels and underpasses helps drivers adjust more quickly to changing light conditions, minimizing potential hazards.
4. Sign Lighting
Sign lighting plays a crucial role in making important navigational information visible to road users, especially in dim or dark conditions. These systems use precise illumination to enhance the readability of traffic signs, directional indicators, and safety markings.
Energy-Efficient Lighting Technologies
The evolution of lighting technology has made energy efficiency a central focus for modern highway lighting systems. Planners can choose from a wide range of options that balance sustainability, performance, and cost-effectiveness.
LEDs
The outdoor LED street light has become the gold standard for highway illumination. Not only do LEDs offer unparalleled brightness and a 50,000-hour lifespan, but they are also energy efficient. For example, they consume far less power than traditional lighting systems. Their lower light degradation over time means fewer replacements and reduced maintenance costs.
Smart Controls
Smart lighting systems incorporate sensors and control mechanisms to adapt to real-time conditions. For instance, dimming capabilities can allow lights to reduce intensity when traffic volumes are low or daylight is sufficient.
Photocells
Photocells can detect the level of natural light and adjust the brightness of highway lights accordingly. This ensures lights are only in use when needed, further optimizing energy use and reducing wastage. By integrating these technologies, city planners can create lighting systems that align with both budgetary constraints and environmental goals.
Mounting Options for Highway Lighting
Selecting the right mounting option for your lighting infrastructure can affect the performance and appearance of the system. Options include slip fitters, universal brackets, and bullhorn mounts. The mounting choice should always align with the lighting and functional requirements of your highway project.
Slip fitters are ideal when flexibility in adjusting the height of the lamps is important. Universal brackets provide support for a wider range of fixtures and lamp types, offering versatility. Bullhorn mounts allow for the installation of multiple fixtures on a single pole, making them ideal for intersections, parking lots, or high-traffic areas where extra illumination is necessary.
Creating Safer Roadways With Smarter Lighting
Highway lighting does more than light the road ahead; it also reduces accident risks, enhances traffic flow, and creates a more pleasant commuting experience for drivers. From understanding the principles of lighting to adopting cutting-edge technologies, this planner’s guide to highway lighting design provides transportation leaders and city planners with the foundation to make informed decisions.
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