Project tests turtle-friendly roadway lighting

Upon hatching, sea turtles instinctively crawl toward the brightest part of the horizon, usually the star- and moonlit ocean. But in heavily populated areas, the hatchlings sometimes become disoriented and head for the bright lights of a well-lit street or residential area. That is a big problem along the Spanish River in Boca Raton, Fla., where hundreds of hatchlings are killed by cars each year.

To address the problem, the Florida Department of Transportation (FDOT) has undertaken a two-year program that officials hope will cut down on the numbers of hatchling deaths. The FDOT program involves the testing of an embedded roadway lighting system. “We’d like to come up with a list of alternative lighting fixtures that could be used statewide,” says FDOT biologist Ann Broadwell.

FDOT selected the design-build team of Kansas City, Mo.-based HNTB and Jupiter, Fla.-based Signal Group to research, design, install and temporarily maintain an experimental system that features asphalt-embedded LEDs and foot-tall lights. Designed to replace street lights, the system creates a yellow glow along a three-quarter-mile stretch of State Road A1A.

The system incorporates short bollards (essentially, low-profile beacons) that protrude 11 inches above the ground on both sides of the street. The lights, which feature a breakaway design, are placed at 30 feet on center and are offset eight feet from the edge of the travel lane (or three feet from the bike lane). Additional lights are situated as close to the roadway as safely possible to provide a reasonable level of illumination for the travel lanes and the adjacent bike lane.

Ocean-side bollards are fitted with an internal shield to block light from emitting towards the beach, and LED lights are placed 60 feet on center along the pavement centerline. “The LED lights embedded in the middle of the roadway delineate the roadway pretty well,” says Kanth Nandam, traffic signals engineer for Boca Raton. “Two-sided LEDs can be effective in marking the turn lanes with appropriately colored LEDs.”

Begun in early June, the $500,000 project will test several different types of embedded lights for two nesting seasons. The results are being studied by researchers at two universities: Florida Atlantic University in Boca Raton is studying the effect of the new lights on sea turtle hatchlings, and the University of Florida, Gainesville, is surveying motorists, pedestrians and cyclists for their reactions to the new lighting system.

Additionally, existing pedestrian light fixtures and lighted street signs are being modified to be more sea-turtle friendly, and other existing light sources in the area have been minimized through support of a public outreach program. The system is designed to be temporary, with the city reverting to its traditional overhead lighting after the hatchlings have left the beach.

Broadwell says that, so far, the lights are getting a positive reaction from the turtles. “Test results indicate that the hatchlings are orienting themselves toward the ocean,” she says.