Smoke and fog can reduce visibility in an instant. On a high-speed road like Alligator Alley, the result can be deadly.

But a new $4.3 million system is intended to warn drivers when weather and road conditions turn bad.

Alligator Alley, which carries Interstate 75 across the Everglades, is prone to the same type of fog that was a factor in the massive pileup on I-75 south of Gainesville early Sunday, which left at least 10 dead and sent 18 to hospitals.

Last year, nine overhead signs were installed along the Alley as part of a safety project, joining five signs already in place. The Alley now has 14 electronic signs — seven in each direction, about every 10 miles.

Electronic signs will be installed on fog-prone U.S. 27 — from Griffin Road to South Bay — starting later this year.

The Alligator Alley project also included six weather stations that collect information on rain, fog and smoke. The weather data is relayed to operators in traffic-management centers in Fort Lauderdale and Fort Myers who monitor the conditions and, if necessary, post warnings on the signs.

“Anything that can help us determine if there is a weather problem and warn drivers ahead of time would be helpful,” said Florida Highway Patrol Sgt. Mark Wysocky.

Any decision to close an interstate is made by FHP.

In addition to weather information, the signs display travel times, Amber alerts and, because they are hooked up to speed sensors, warn drivers if they are over the speed limit.

In 2010, the state started using electronic signs on interstates in South Florida to display warnings from the National Weather Service for severe thunderstorms, tornadoes, hurricanes, tropical storms and fog.

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

Fog, which typically occurs in the Everglades during the winter months, has not been an issue so far this year, Wysocky said.