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State DOTS Reduce Energy, Costs, and Risks with LEDs

Caltran's LED lighting on the Richmond-San Rafael Bridge
Caltrans’s light-emitting diode (LED) lighting program, which was pilot-tested on the Richmond-San Rafael Bridge, will save California an estimated $2 million annually statewide through reduced energy costs, while increasing safety for workers. Courtesy of Caltrans 

As state departments of transportation consider every option to reduce costs while not impacting service, many are turning to longer-lasting, energy-saving light-emitting diode (LED) light bulbs—and are finding some illuminating results. 

May 22, 2012—In these difficult financial times, as state departments of transportation (DOTs) seek to make up for budget shortfalls, the resounding lack of commitment by the federal government to any increases in the federal gas tax, and delays in the reauthorization of the federal transportation funding mechanisms, many have discovered that going “green” can also save them some “green.”

From California to Texas to Rhode Island, state DOTs have begun to replace the traditional high-pressure sodium (HPS) light bulbs they use in street and bridge light fixtures with light-emitting diode (LED) bulbs, which can last anywhere from two to five times longer than HPS bulbs and dramatically cut energy costs during operation. By some accounts, the LEDs emit a warmer light than the HPS bulbs, can fit directly into the same fixtures in some cases, and can reduce the risks to maintenance crews by requiring far fewer changes. “This technology has a much longer life cycle,” says Tony Tavares, the chief of the division of maintenance for the California DOT (Caltrans).

The entire State of California is attempting to reduce its greenhouse gas emissions significantly by 2020 in compliance with its Global Warming Solutions Act, passed in 2006. By replacing all of the state’s highway HPS light fixtures with longer-lasting, more energy-efficient LED bulbs—which it hopes to do over the next several years—Caltrans will contribute toward this goal, Tavares says. “LEDs are another tool we have in our toolbox to help California reduce its carbon footprint,” he says. “We are being told that the new LEDS can save anywhere from 30 to 50 percent in energy costs.”

Rhode Island’s recent experience bears this out. Robert Rocchio, P.E., the managing engineer of the traffic division at the Rhode Island DOT, said in written responses to questions posed by Civil Engineering online that a pilot test conducted in July 2010 in East Providence resulted in energy costs that were cut in half. The test compared newly installed HPS lights against new LED lights. “We wanted a fair comparison of both technologies at peak performance,” he said. “Based on the results, we are planning to roll the technology out statewide as we replace existing lights or install new systems along our limited-access highways.”

Caltrans also pilot-tested the switch, on the Richmond-San Rafael and San Mateo bridges. Beginning in 2007 the department replaced all the overhead lighting on both spans with LEDs, and even though those bulbs are now considered to be older, less-efficient versions of the technology, the tests were considered a huge success, Tavares says. “It was successful at reducing the exposure of my employees from having to be out there [so often] to change those lights, and it also reduced costs,” he says. The 2007 LED bulbs were expected to last twice as long as the HPS lamps they replaced, which had a life span of three to four years, Tavares says. Newer versions of the bulbs are expected to last 15 or even 20 years. “It’s a huge improvement,” Tavares says.

In fact the bulb technology has advanced so far in just the past five years that the bulbs may outlast the fixtures that hold them. Greg Jones, P.E., an electrical engineer in the Traffic Operations Illumination Group of the Texas DOT, says that manufacturers have told him that their bulbs will last 60,000 hours—but the fixtures into which they are placed are currently only rated for about 50,000 hours. “That’s a concern,” he admits, although he suspects that newer fixtures will last longer. Roughly five of the Texas DOT’s 25 districts have opted to try LEDs as they conduct regular bulb replacements, Jones says. “Right now we are doing it as a special specification, but after we see how this works, we may make it a standard specification and leave the districts the option.”

Both the Texas and Rhode Island DOTs are finding that they must replace entire fixtures, not just the bulbs, as Caltrans has been able to do. Even so, Rocchio expects that the Rhode Island DOT will save $1 million by installing LED fixtures, “recouping our investment in about five years,” he said. “That would come from energy savings as well as savings in labor and materials because the bulbs are replaced three times less frequently than traditional lighting.” Rocchio expects Rhode Island’s program to begin in 2013 and take 10 to 15 years to complete.

To pay for California’s statewide program, Tavares is taking advantage of the fact that California avoided a harsh winter this past season; money that wasn’t spent on snow removal is being funneled toward purchasing LED bulbs. Tavares says he’ll use those funds plus his regular allotment for HPS bulbs to purchase 40,000 LED bulbs beginning on July 21st, the start of the state’s fiscal year. “So it’s not an increase to the taxpayer,” he explains.

Caltrans will then spend several years actually making those replacements. “We’ll do the big purchase now and receive the shipments throughout the next couple of years,” he says. The program is expected to save California an estimated $2 million annually statewide through reduced energy costs.

As an added bonus, Tavares says that the quality of the light emitted by the LED bulbs seem to be more pleasant. “Several of our municipalities have replaced their traditional lighting with LEDs, and all of the feedback I have been hearing is very positive,” he says. “It’s a different color but more of a warmer light. It’s easier on the eyes, especially at night.”

Between the energy savings, the cost savings, the safety benefits, and the reduction in eye strain, Tavares says, LED technology offers “a huge benefit to everyone.”


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