When the aesthetic lighting is tested on the new Iowa-bound arches of the I-74 bridge, cellphone pictures get instant social-media attention.
The alternating colors cast a glow upon the arches, the roadway and the Mississippi River below. By the end of the year, transportation officials estimate, the aesthetic lighting should be on and fully operational on the Iowa-bound bridge.
The span opened to two-way traffic late last year, and its LED lighting so far has only been tested. The Illinois-bound span, which is to open in December, is to have its aesthetic lighting operational by early spring or summer.
Meanwhile, several staffers in Bettendorf are learning how to use the lighting systems, which come with their own computer server, housed at Bettendorf City Hall.
"We should be able to pre-program the lights for a year in advance," said Decker Ploehn, city administrator. "We'll have an agreement with Moline on what light combinations to use for each holiday."
The lighting system was designed by a team from New York City-based HLB Lighting Design and Chicago-based engineering firm Alfred Benesch & Co., which designed the bridge.
While overhead lights provide safe entrances and exits for the twin spans, each will have more than 100 fixtures, mounted to the floor beams, to supply the aesthetic lighting for the arches.
The light, in other words, shines upward, rather than down. The floor-level fixtures contain LED chips, and the glow of the luminaries follow the suspension cables. The chips and their circuitry provide the illumination, rather than traditional filament and bulbs.
"The best way to highlight the structures was to go under the ribs (arch segments) ... to help it look its best," said Elizabeth Johnson, project manager/designer for HLB.
The three primary colors in use — red, green and blue — appear at varying intensities through dimming, which creates countless colors and combinations of color.
In the decade that has passed since teams began designing the aesthetic lighting for the new I-74 crossings, technology and the bridge's surroundings have changed.
At first, the neighboring Bettendorf City Hall was chosen to house the lighting server, because its wireless controller needed line of site, and Bettendorf's is better than Moline's, said Geoffrey Thiesse, lead electrical engineer for Alfred Benesch & Co.
While construction of a multi-story housing complex next to the bridge disrupted the line of site, a switch to fiber optics eliminated the need for it, he said.
The system is intended to be easy to use, and training is provided, Johnson said.
Faith Baum, principal in charge at HLB Lighting Design, said the system will supply an enormous number of color combinations, explaining that mixing light is different from mixing paint.
"The difference is that light mixes to create more light," she said. "You can't make brown."
The colors, through programming, can be static or dynamic. Changes must occur slowly, though, Baum said, so they don't distract motorists.
Additional aesthetic lighting will be seen in the spans' "identity elements," such as the rectangular, sculpture-like beacons that appear at several locations. The overlook on the bike/pedestrian path also will have its own aesthetic lighting, including for the oculus that will allow visitors to look through the path floor to the river below.