The Tennessee Highway Patrol is encouraging people traveling along I-40 to be cautious, especially at night.

Troopers are investigating after 15 cars were damaged by rocks thrown from an I-40 overpass.

Amy Simpkins said she travels along I-40 three to five times a week and doesn't understand why people would do something so dangerous.

"Driving a car is dangerous enough. We don’t need people throwing rocks at our cars making it that much more so," Simpkins said.

The reports started coming in on July 19. Some people driving on I-40 East in Roane County near the Buttermilk Road exit between mile markers 362 and 366 said their vehicles were hit by rocks thrown from an overpass.

Most of the damage was minor, but one vehicle had to be towed. Luckily, no one was injured.

THP has no suspects at this time and said it's difficult to solve these kinds of cases unless someone comes forward or sees something.

Simpkins said she's hoping someone comes forward to help THP get to the bottom of it.

“That’s just such a dangerous situation," Simpkins said. "I think the best thing we can hope for is that somebody actually has, a camera on their car and can catch surveillance, because when you're driving through an overpass at what 65 to 70 you're not gonna be like "Oh, there's a person."

Simpkins said her husband spends a lot of time on the road as a truck driver, so this situation is especially worrying to her.

"He risks his life every day," she said. "He doesn't need the added risk on top of it."

Troopers worked with the impacted motorists on reports to help them with their insurance claims.

In the meantime, officers said people should use caution when driving in these areas -- particularly after dark.