Pittsburgh, Pennsylvania, has more than 35,000 overhead streetlights, including many that are old and historic. Some are cobra-head light fixtures that extend over the street, with different mast arm lengths, heights, and orientations. Others are decorative and come in various shapes and sizes.
The city also has significant elevation variability. For example, Pittsburgh’s Canton Avenue has a 37 percent grade, making it the steepest officially recorded public street in the United States. To light this street properly, the lighting at the top of the hill must not distract drivers by shining directly into their eyes.
When city staff members created a plan to install 3,000–15,000 new streetlights, they needed maps that showed not just the locations of existing and proposed streetlights but also where lighting was most needed. In addition, mobility experts required lighting data to evaluate lighting on infrastructure such as bike lanes, and environmental professionals needed information to assess lighting impacts on protected and sensitive habitats across Pittsburgh. City staff also had to determine where to add or remove lighting and evaluate which streetlight manufacturer to choose.
All these requirements called for implementing a new GIS solution—a specialized ArcGIS Pro script tool created for the project by Esri partner Evari GIS Consulting.
Adjusting to Twists and Turns
In general, utility or traffic engineers employ the same computer-aided design (CAD)-based tools that are often used for indoor lighting to decide where to install streetlights. Street and roadway lighting designs are based on 10–20 typical layouts that represent various public rights-of-way. For example, lighting a four-lane arterial roadway is usually done in the same way everywhere in the United States, regardless of context.
While this process generally works, it doesn’t account for Pittsburgh’s complexities, including the city’s elevation variations, twists and turns, and mix of decorative and utilitarian lights. So city staff began considering a more innovative, context-sensitive approach to complement conventional designs.
Using GIS for this seemed like a good option, but there was a problem. GIS has often been used to show streetlight locations—and sometimes even connections to circuits and other aspects of the electric grid—as mapped points. But it was much less common—if it had ever been done at all—to show, at scale on a map, the distribution of light from street lighting.
A New Way to Analyze Lighting
To help optimize street lighting for Pittsburgh’s particular conditions, a team at Evari developed a specialized ArcGIS Pro script tool called EvariLUX that assesses ground-level illumination using standard lighting specification files. The tool integrates horizontal and vertical angles from these files with elevation data from the US Geological Survey’s 3D Elevation Program to calculate light distribution from streetlights.
The resultant 3D “illumination surface,” generated in ArcGIS Pro, is hosted in ArcGIS Online and expressed by points and contours with scale-dependent symbology. This allows lighting designers to quantify how much illumination reaches the roadway, bike lanes, sidewalks, and private property. It also lets city staff analyze the data at small and large scales.
Using GIS-native data related to the streetlight infrastructure and the quantity of lighting across the city, the Evari team also examined street lighting inequities from neighborhood to neighborhood. For each neighborhood, the team considered nighttime and twilight collision history, environmentally sensitive areas, land-use needs, the presence of bike lanes and transit stops, proximity to schools and parks, and historical redlining—the practice of denying services to neighborhoods that have large racial and ethnic minority populations. The Evari team conducted these comprehensive analyses using ArcGIS Pro.
To evaluate collision history, the team considered a US Federal Highway Administration guideline that recommends upgrading lighting if at least twice as many traffic disruptions occur when lighting provides visibility compared to during daylight hours. Streetlight improvements can reduce collisions by up to 42 percent, according to Federal Highway Administration estimates. Using multiyear crash data, the team from Evari found that this guideline applied to 281 intersections across Pittsburgh.
Once the project team determined proposed lighting levels throughout the city, it compared existing lighting levels to each lighting manufacturer’s designs and specifications. The team used a web app built with ArcGIS Experience Builder to create directly comparable web maps for each manufacturer’s products, including how they would work in challenging locations such as Canton Avenue or Pittsburgh’s major-league baseball stadium. Evaluation metrics for each lighting product included the following:
- Does it deliver the most illumination to the public right-of-way?
- Will it create the least light trespass, meaning the light and energy that leaves the right-of-way?
- Does it address nighttime high-frequency crash locations?
- Can it improve lighting conditions in underserved areas?
Tangible Benefits for Urban Areas After Dark
When city staff members compared street lighting gaps with the illumination results from Evari’s script tool and specific lighting options from different manufacturers, it became clear that the city only needed to install about 1,100 new streetlights throughout Pittsburgh while upgrading others.
In addition to reducing construction costs by millions of dollars, this GIS-based approach has enhanced city staff’s ability to make informed, data-driven choices. Likely benefits from this project will include millions of dollars in savings; the prevention of injuries and deaths on roadways over the lifetime of the fixtures; and improved quality of life and travel for people walking, biking, riding on public transit, and driving around Pittsburgh.
About the author
