PROJECT FIXTURES & CONTROLS

The Metropolitan Government of Nashville and Davidson County is embarking on a transformative project aimed at upgrading its existing streetlight infrastructure. The initiative involves replacing outdated fixtures that use inefficient high-pressure sodium, mercury vapor, and metal halide lighting technologies with state-of-the-art LED fixtures. These new fixtures deliver numerous benefits—for example: enhanced visual acuity, reduced energy consumption, lower maintenance costs, and an extended lifespan. 

A streetlight’s form will usually fall into one of a few major categories: a “cobrahead”, an interstate high mast, an offset, an area light, a teardrop, or a decorative (like a post-top). A streetlight’s selection is often further prescribed by its intended use: the street classification and the distance from the road are a few of the major considerations. Roadway fixtures are further specified by functional classification of the roadway (e.g. Local, Collector, Major) where it will be installed. Historically, Nashville’s utility provider (Nashville Electric Service “NES”) has had one approved streetlight manufacturer and model for each level of lighting required by each fixture type. The fixture selections have been formalized in a detailed “Lighting Guideline document” that is readily available and posted online; it is in its sixth revision and includes standards, construction details, and installation processes, along with other relevant parameters (poles, controls, maintenance, etc.). This Guideline document was used for the project’s original basis of design for each fixture’s LED replacement when the project was in its early stages.

NDOT approved the addition of new fixtures in all phases of the metropolitan Nashville streetlight conversion project and to be included in the next revised publication of NES’s Lighting Guidelines. The project considered the original basis of design and newer alternates with updated performance along with the previously-approved characteristics like optics, warranties, performance guarantees, maintenance requirements, and ease of installation. The typical fixture installed in the project is manufactured by a “tier-one” vendor, has a DLC certification, a UL listing, a 10-year warranty, minimal uplight, dimmable down to 10% output, and a NEMA 7-pin controls receptacle. Although each fixture’s output and optics specification varies based on the location, they typically are all 3,000K CCT (or lower) and meet DarkSky requirements. Product manufacturers selected for this project include American Electric Lighting, Cooper, Holophane, US Architectural Lighting, HADCO, Acuity, Signify, Ubicquia, and Trellix to name a few.

In addition to Metro’s fixture conversion, the project includes a transition from traditional on/off photocell controls to a cutting-edge digitally networked smart-city technology. This entails the installation of control units or "nodes" atop each streetlight, communicating with a centralized control system. Through the control system's dashboard, these streetlights can be remotely monitored for power outages, malfunctions, and other incidents such as knockdowns. Moreover, they seamlessly integrate with broader smart-city initiatives, contributing to the creation of a cohesive and interconnected urban infrastructure. This technology allows for specific light output settings, enabling efficient energy management and adjustments for safety purposes.

These expanded inclusions will provide the Metropolitan Government of Nashville and Davidson County with high-quality and thoroughly-vetted options for their new LED streetlight fixtures and networked controllers for many years to come, ensuring success for this project and future projects also. Some typical depictions of the project’s fixtures and controllers are shown below.