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Bay Bridge: Cutting edge LED lights create unique night landscape

Friday 06 September 2013

OAKLAND -- In daylight, the new Bay Bridge's iconic white tower and suspension cables gleam in a panoramic landscape saturated with deep hues of earth, water and sky.

But for nocturnal motorists, the span's tens of thousands of icy white LED lights strung on the suspender rope canopy, looping catenary cable and soaring tower is a journey onto a rocket launchpad magically suspended in blackness.

Engineers and architects created the outer space sensation with a combination of light, dark and steel. The journey begins while traveling westward from Oakland on the new $6.4 billion span that opened Monday night. The roadway is illuminated in a soft white glow from the rows of white free-standing light poles that line the skyway's side-by-side decks.

Directly ahead is the new span's dominating feature: a 525-foot tower lit with floods, its alternately vertical and horizontal architectural design fashioned with the Saturn V rocket in mind.

Light sweeps along the thick main cable and plunges vertically down the suspension ropes, bathing the travel deck in continuous white light.

"It is something, isn't it?" said Bay Bridge lighting engineer Saeed Shahmirzai as he stood on the traffic-free travel deck after dark a few days before the bridge opened.

Shahmirzai is also the lead engineer for the Bay Lights art installation -- the world's largest LED light sculpture -- on the western half of the Bay Bridge. But the eastern span's state-of-the-art lighting system is more than eye-catching -- it is permanent and designed for the motorist as much as the architect.

Iowa-based Musco Lighting, internationally renowned for its sports stadium and movie lighting systems, pre-aimed each of the span's 48,000 individual LEDs and its 1,521 fixtures using computerized lighting design software.

The company built a scale Bay Bridge model at its Oskaloosa headquarters to analyze the lights' spread and ensure it would cover the wide span's decks. As a result, the lighting is uniform and illuminates the roadway in front of the motorist like a set of headlights rather than the series of light pools found beneath conventional streetlights.

A decade ago, lighting architect and engineer Howard Brandston recommended sodium vapor lamps for the new span.

Used worldwide for their relatively low cost and high efficiency, sodium vapor bulbs such as the metal-halide lamps on the existing Bay Bridge have for years illuminated streets and parks.

But in the decade since Brandston devised the lighting plan for the iconic span, light-emitting diodes, or LEDs, have come into their own. Once regarded as too expensive and too dim, the LED bulb's 10- to 15-year life span compared with 2 years for a sodium lamp, coupled with declining prices and improved technology, is propelling their use.

Shahmirzai ticks off the LEDs' other major advantages: Much more efficient. A 650-watt LED delivers the same illumination as a 1600-watt conventional bulb, for example. Less light pollution and no mercury. Lower maintenance costs. In addition to the longer-lasting bulbs, each Bay Bridge light pole is equipped with an antenna and technicians can access and adjust every fixture with a laptop. Plus, Musco's bid included a 10-year warranty on all parts and labor. Even so, when talk of converting to LEDs started more than five years ago, Caltrans bridge engineers, project consultants at TY Lin/Moffat & Nichol and architect Donald MacDonald wanted more out of the lights than the technology could deliver, Musco sales manager Adam De Jong said.

"They wanted uniform light for the motorists without spillover or light pollution," De Jong said. "And they wanted the lighting to look clean and aesthetically preserve the ribbon of white light across the bay. What they wanted at the time, as far as where the technology was, was unattainable." When designers initially looked at LEDs, each light pole would have needed to be nearly three feet in diameter to hold enough bulbs to illuminate the new bridge's five lanes and two shoulders. But bulking up the sleek new span with light fixtures the size of dining room tables wasn't an option, De Jong said. The key, he said, was vastly improved LED chip technology that boosted maximum per bulb lumen, or light, levels. "I thought the architects might throw something at us," he said. "But we were able to get the (pole) barrel diameter down to 16 or so inches and still provide ample illumination and glare-prevention." Although Musco offers a popular remote operations service for its clients that turns their lights on and off according to a schedule, that won't happen here. In fact, only two of Musco's clients run their own light show: the White House and the Bay Bridge. "It's a security issue to have someone in Iowa remotely turning the lights on and off at the White House and the Bay Bridge has the same concern," De Jong said. "But I'm pretty sure that when there's a big game at a Yankee Stadium, they have the lighting system in manual mode." LIGHT 'EM UP The Bay Bridge is Musco Lighting's first major bridge, but the company is a giant in other arenas. Its systems illuminate players and fans in more than two dozen baseball, football and motor sports stadiums throughout the world and the United States, including Yankee Stadium in New York, Lambeau Field in Wisconsin and the Daytona International Speedway in Florida. The company is also known for its motion picture lighting equipment, and it has illuminated Super Bowls, Olympics and the Statue of Liberty.

Here's a look at the numbers behind the Bay Bridge lights: 273 -- Number of light poles 23 to 65 feet -- Light pole heights 1,521 -- Number of light fixtures 25 to 50 -- Number of light-emitting diodes, or LEDs, per fixture 48,000 -- Total number of LEDs on the bridge 50 percent -- Energy savings gained with the use of LEDs compared with sodium vapor bulbs, the type of lighting used on the original span. 10 to 15 years -- LED life span compared with 2 years for the sodium vapor bulbs on the existing bridge.


  1. Mercury News:
    Toll Bridge Program Oversight Committee.


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