Alligator Alley’s new system knows when you’re speeding

System tracks motorists’ speeds and post alerts to slow down on electronic signs

October 20, 2011

New electronic signs on a stretch of I-75 in Florida will clock drivers’ speeds and post alerts in an effort to reduce fatal speed-related crashes, according to

The state is testing a new system on Alligator Alley, which carries I-75 through the Everglades, that will post an electronic message on signs above the highway if a driver is going even 1 mph over the 70-mph posted speed limit.

Alligator Alley is prone to drivers who exceed the speed limit with its long, wide-open stretches –– and the deadly crashes that can accompany high speeds.

About 85% of traffic whizzes by at 84 mph –– 14 mph over the speed limit, according to a recent study. Troopers routinely clock drivers exceeding 90 mph.

Officials hope the new signs will get drivers to slow down. But they acknowledge that it is a test and they don't know if it will work or how drivers will respond.

The signs will not display drivers' speed, issue tickets or alert Florida Highway Patrol (FHP) troopers. But it is hoped that these more drastic steps are not necessary to get drivers to react.

In 2008, Florida's Turnpike officials installed smaller digital speed limit signs on the Sawgrass Expressway in Coral Springs, where the north-south highway turns east-west. The roadside signs display drivers' speed if they go 5 mph over the 65-mph speed limit.

Officials wanted to draw more attention to the speed limit on the only significant curve in the 23-mile-long toll road.

Motorists seem to be getting the message. In September, the average speed at the signs was 71 mph in the northbound lanes and 65 mph in the southbound lanes. Other straight stretches of the Sawgrass where speed is measured on the Sawgrass ranged from about 75 mph to 81 mph.

"The lower speeds cannot be entirely attributed to these (signs)," said Sonyha Rodgriuez-Miller, a turnpike spokeswoman. "However, we do expect they assist in reminding motorists to their speed."

The technology has changed driver habits elsewhere in the country. In Garden Grove, Calif., a Los Angeles suburb, officials turned to the speed display signs after increased enforcement did not curb a problem with speeders in a school zone.

Although the signs provided information that was already available to drivers on their own speedometers, the experiment worked. Driver speeds dipped anywhere from 6 to 22%, according to a city study.

The theory is that feedback loops, in which people get real-time information about their own activities, can have a positive influence on human behavior and be more effective than a police officer with a radar gun.

The Alligator Alley signs will tell drivers if they are over the speed limit with a message such as "Left Lane Over Speed Limit Slow Down."

The state spent $4.3 million to install nine new signs and enhance five existing signs with the new technology. The radar component cost about $273,000.

The project also included six weather stations to monitor smoke, fog, rain and wet pavement conditions; weather information also can be displayed on the signs to inform drivers of reduced visibility.

About 22,500 vehicles a day travel Alligator Alley between Weston and Naples.

About the Author

Related Articles

The Idaho Transportation Department (ITD) this week will deploy variable speed limit signs within the I-84 construction zone in Canyon County in…
August 11, 2021
Improving Safety with Intersection Conflict Warning Systems
All images: Indiana DOT
Intersection Conflict Warning Systems (ICWS) are improving traffic safety across Indiana by reducing the likelihood of severe vehicle crashes at some…
May 21, 2021
Wrong way sign project begins on southern Arizona interstates
Image: Arizona DOT
The Arizona Department of Transportation (ADOT) is beginning a project to install larger, more visible wrong way signs along southern Arizona’s three…
May 19, 2021
PennDOT begins posting variable speed limits on on I-76 Schuylkill Expressway
Image: PennDOT
The Pennsylvania Department of Transportation (PennDOT) has recently posted Variable Speed Limits (VSL) and Queue Detection and Warning (QDW)…
May 12, 2021