Heavy fog forced troopers to shut down several miles of I-75 for a little under an hour on Tuesday morning. This happened just days after the 25th anniversary of the fog-related crash that killed 12 people in a 99-car pileup back in 1990.

Officers with Tennessee Highway Patrol reported that visibility went down to 250 feet on Tuesday. Drivers we spoke with could barely see anything in front of them.

TDOT cameras show an empty interstate, just after rush hour, after heavy fog caused several miles of i-75 in northern Bradley County to shut down.

A photo, taken by Channel 3 viewer, shows the view from behind the wheel near Charleston. The cars in front of it are barely visible.

"Once it gets below a certain point of visibility, it is no longer safe for the motoring public to be out here on this roadway," said THP Lt. Carey Hixson.

Around 9 a.m., THP officers reduced the speed limit in the fog zone to 50 miles-per-hour. Within 20 minutes, visibility on the interstate was reduced to just 250 feet.

"Since the fog continued to get worse, we had to shut it down," Hixson said.

Troopers began diverting traffic at mile marker 27 in Cleveland to avoid the fog zone. Traffic rerouted to Highway 11 until the interstate re-opened about an hour later.

Priscilla Goodwin sells merchandise in a tent, just off the Charleston exit. She said conditions were bad during her drive.

"When I pulled up, I thought there might have been a bad wreck or something, because all kinds of lights going," Goodwin said. "The off ramp was closed. We couldn't even get in here."

Goodwin thought the worst when she saw the police presence, thinking back to the deadly fog crash 25 years ago.

"December 11th was the one that was right here, where all the people got killed," she remembered.

After 12 people lost their lives that day in a 99-car pileup, THP says they can't be too safe.

"We really want to make sure nothing happens like it did in 1990," Hixson said.

In addition to TDOT cameras and fog monitoring centers, a trooper is assigned to the "fog zone" area every day to help monitor conditions. The trooper on duty Tuesday helped make the call to reroute traffic.