- Associated Press - Saturday, March 22, 2014

ST. CLOUD, Minn. (AP) - Finding the perfect street light is no simple task.

New lighting technology means engineers can choose lights based on how widely the light is transmitted, the color of the light and the extent of shadows and glare. So a neighborhood can have a warm, cozy feel while intersections can be brightly lit while limiting glare.

“It’s like comparing a guitar player to an orchestra,” Traffic System Manager Blake Redfield said of the new technology.

LED lights give cities a number of options to find street lighting that best serves the area they are in. And St. Cloud has an unusual lab where those lights can be tested so the most efficient ones are purchased and put on city streets.

Redfield, who works for St. Cloud and Stearns County, created the lab three years ago to test the quality of LED street lights. The city was looking to put lights on Kilian Boulevard, and Redfield said they heard “outlandish” claims from manufacturers about how well LEDs worked.

So the city created its own to test the lights and find out how well they work.

“We wanted to do our homework and we did,” he told the St. Cloud Times (http://on.sctimes.com/1gH3exI).

Starting this year, St. Cloud plans to put LEDs in all new street lights. While more expensive up front, LEDs only need to be replaced every 10 years, compared with every three years for traditional lights. Putting in LEDs can increase a project’s price by about 15 percent.

“They’re expensive, so we want to make sure we get the best bang for our buck,” Redfield said.

And the improving technology has lowered costs of LEDs over time. Four years ago, a LED street light would cost $1,300, but now the cost averages $250.

“Now we almost can’t afford not to put in LED,” he said.

To make sure the city is purchasing the best lights possible, Redfield puts them through several tests that he designed. In the past, Redfield has found light patterns that are not symmetrical and lights that create a shadow around the light pole.

One test uses a light deck, which is a platform with a series of holes on it. At each hole, the light’s intensity can be tested so Redfield knows how well the light shines directly below the lamp and further away from it.

He also can test how much light can be seen above the fixture, which is important for limiting light pollution.

The lights also are put on a light tower, which can move it up to different heights. That allows him to see how wide the light spreads out and if the light is uniform.

A wider light pattern is used at intersections while a narrow pattern would be used down a main open stretch of road. The LEDs prevent hot spots or dead spots in the light along a road.

“We’re only putting light where we need it,” he said.

An electrician also comes and takes apart the lights so they can see how easy it will be to maintain them.

The testing goes beyond taking data. Redfield has written a program to create 3-D photo metrics that show the light’s intensity and uniformity.

The setup is so well done that manufacturers bring in lights to get feedback from Redfield’s testing.

The use of LEDs is apparent at several sites around the area.

Residents can notice the light changes while driving through the Stearns County Road 120 roundabouts near Minnesota Highway 15. While driving, the road will remain dark until you approach the roundabout, which is brightly it.

Redfield also designed the street lights for the new roundabout planned for Stearns County Road 133 and 19th Avenue in Sartell. He said it will be brightly lit because of the high speeds on the roads, but using LEDs will prevent light from polluting the surrounding rural area.

The park and ride lot in St. Joseph also has LEDs that can dim when the lot isn’t in use. There are monitors at the site that detect whether a vehicle has come into the lot. If it has been more than 15 minutes since a vehicle has driven into the lot, the lights will dim. Redfield said it takes a full minute for the lights to dim and you wouldn’t notice it unless you were looking for it.

The Kilian Boulevard project was the first one done in St. Cloud. There were some complaints that the lights were too bright. Different lights were put up on Riverside Drive and there have been no complaints about that project, he said.

Having the ability to test them allows the city to use the best lights possible.

“We want to make sure we have good (street light) projects,” Redfield said.

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Information from: St. Cloud Times, http://www.sctimes.com

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