News

Jul 02, 2023

How to best light a road? It’s all about math and bulbs

South Florida’s vast road construction projects are about more than just

South Florida's vast road construction projects are about more than just asphalt, bridges, signage and toll lanes.

Lighting is an equally key component.

There's a formula that determines which lights go where for the best illumination and what's easiest on the eyes of drivers, said Barbara Kelleher, with the Florida Department of Transportation.

Most roadways use high-pressure sodium bulbs that produce a pink-orange light. Metal halide is a brighter white light popular with more decorative, custom city street lights, said Yves d’Anjou, with Broward County‘s Traffic Engineering Division.

But, he said, LED is gaining ground.

"Research seems to be indicating drivers’ eyes respond better to the warmer spectrum of LED's [yellow-white] light than the earlier blue-white spectrum range," he said.

Placement of the poles is another issue.

"There's different criteria for under bridges and over overpasses. It's complex engineering," Kelleher said. "It's a mathematical equation."

At the Spanish River Boulevard exit under construction on Interstate 95 in Boca Raton, at least $2 million has been budgeted for lighting.

There will be 174 new highway poles installed on I-95 and at the exit ramps. Twenty-six more poles will be relocated along Yamato Road and 45 lights will be installed under overpasses and ramps.

Sometimes, adjustments are made.

In October, the state installed 81 high-mast lights along a stretch of Interstate 75, north of Weston, to provide more light to a larger area of the highway between the Alligator Alley toll booths and the I-595/Sawgrass Expressway interchange.

"We have light meters, [and crews] inspect them at night, obviously, to make sure they are working properly," Kelleher said. "When the lights are new, there's a 24-hour ‘burn in’ period for seven days to make sure the circuits are working and all the lamps are working and the [light] sensors are working."

Broward, Palm Beach and Miami-Dade counties each have at least 100,000 street and highway lights.

Most are on 25- to 40-foot aluminum poles, while interstate highways generally have 100-foot, high-mast poles near interchanges and exits. The light bulbs can be the size of a basketball and weigh more than 40 pounds.

Several South Florida municipalities have been working to replace old street lights with LED lights that are brighter, longer-lasting, and cheaper to power and maintain over time.

LED lights can last up to 70,000 hours compared to 13,500 for metal halide.

The maintenance of street and highway lights is shared between city and county utility crews, the state and Florida Power and Light.

[email protected] or 954-356-4303

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Where to report outages

To report a street light outage, call FPL at 1-800-468-8243 or go online to FPL.com/streetlight.

To report highway light failures, call FDOT at 954-777-4090 or email: [email protected].

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