Jul 18, 2022
Is the Glover Cary Bridge a case study in dazzling design or cutting-edge technology? The answer is yes and yes
By Paul Tarricone

Photos: Jason Tanner

There were plenty of “oohs” and “aahs” when the architectural lighting for the Glover Cary Bridge connecting Owensboro, KY, and Spencer County, IN, was unveiled for the first time. An eight-year project timeline at a cost of $1.9 million culminated in a vibrant celebration in late 2020—albeit scaled down due to the pandemic. 

But there’s one thing those folks who watched the color-changing extravaganza may not have even considered: who’s controlling the light show? In fact, design and control were equal partners on this project, which earned 2021 IES Illumination Awards of Merit in both categories.

First, is what meets the eye—the design. A total of 512 individually addressable LED luminaires (Signify Color Kinetics) create the color effects on both sides of the 2,000-ft-long bridge. “Luminaires were installed on each end of the horizontal and vertical structural beams. Intermediate luminaires were installed at the midpoints of the longer beams. Straps were used to support the luminaires, while clamps were used to install raceways to avoid welding, which was not permitted,” says Michael Krosky, senior associate and electrical project engineer with AECOM, Cleveland.

Blue LED lighting is the everyday setting to match the blue-painted steel bridge, while multiple static and dynamic color scenes can be programmed by the city for special events and holidays. To ensure visual comfort for spectators viewing the light show, adjustable luminaires with 8-deg optics were selected to highlight the beam façade. Tightly mounted to the beams, the luminaires emit just a small amount of residual spill light, thereby reducing glare for the comfort of those driving on the bridge. Field aiming the luminaires optimized contrast and uniformity ratios. 

“The design also planned for future expansion,” Krosky adds. “It accounts for 512 DMX channels but has the capability of utilizing 2,048 channels. This gives the client the opportunity to provide three-to-four times as many lights without upgrading the communication or power infrastructure.”

Second, is what’s behind the scenes—the controls strategy. Dedicated Internet service from the utility “was an absolute necessity,” says Krosky. “This allows the city to control the lighting remotely.” The engineering team also had to decide between a wired or wireless design. Knowing any control point was only as strong as its weakest link, repeaters failing due to inclement weather could potentially diminish any signal along its path. “A wired solution seemed to be the only successful design path,” Krosky explains.

Another challenge was providing communication cabling over a 2,000-ft span of bridge when copper cabling is limited to approximately 984 ft (300 meters). As a result, “we used fiberoptic cabling that can literally run for a mile with little to no loss in signal,” says Krosky. “At strategic points along the bridge, localized control cabinets were placed to transition from fiber to copper, which minimized any potential losses. This communication cabling allowed the luminaires to be individually addressable to program the multiple static and dynamic scenes.”

The bridge’s location—spanning the Ohio River between Kentucky and Indiana—posed a challenge in terms of power supply. In a perfect world, panels would be placed on each end of the bridge. But since the bridge is owned by Owensboro, power can only be fed from the Kentucky side. “Our solution used a step transformer from 240 volts to 480/277 volts; three-phase and alternate phases for the luminaires; and increasing wire sizing to ultimately have 480-V, three-phase circuits back to the lighting panel,” says Krosky. “This yielded less than 3% voltage drop to the last luminaire on the 2,000-ft span. In terms of power expandability, 25.92kW is connected to a 63kVA transformer which allows the client to add lights to this bridge without upgrading the utility service.”

The U.S. Coast Guard usually doesn’t find its way into a lighting installation, but it played an important role here, as the controls strategy also extends to the Ohio River. “There is existing navigation lighting located along the entire bridge span controlled by the Coast Guard, which takes precedence over the aesthetic lighting,” says Krosky. To ensure safety, a radio control unit allows the Coast Guard to turn the navigation lights on or off. “The intent is that if the lights need to be clearly visible to the Coast Guard, a radio signal could ‘talk’ to the light panel and turn off the lights for a period and turn them back on for normal operation.”

Finally, a light show wouldn’t be complete without music. Controlled of course. Whether it’s live or recorded music, an audio input can control the color and intensity of illumination based on the amplitude and tone of the music. Synchronicity at its finest.

THE DESIGNER

Michael Krosky, PE, LC, Member IES, is senior associate and electrical project engineer with AECOM, Cleveland.

Contributor(s)

Paul Tarricone

Paul Tarricone

Paul Tarricone has more 25 years of experience in association and business-to-business publishing, specializing in the engineering, design, construction and facilities management markets. Mr. Tarricone currently serves as Editor and Publisher of Lighting Design + Application,... More info »