St. Clair County Coroner Dennis Russell identified the victim as Terry Shane Mobley, 39, of Cropwell, who was pronounced dead at the scene.
The victim’s sister, identified as Vickie Walker of Pell City, was transported to UAB Hospital in Birmingham by a Lifesaver helicopter.
A spokesman for UAB Hospital said Wednesday night that Walker was listed in fair condition.
Russell said the Mustang GX Mobley was driving left the interstate and traveled about 500 feet before striking a metal guardrail.
He said the vehicle rolled over, killing the driver, who was wearing a seatbelt at the time of the fatal crash.
Riverside Volunteer Fire Department Paramedic Rachelle Painter said the accident happened shortly after 3:30 p.m., on the eastbound lane of I-20.
The accident happened about one mile west of the Riverside exit.
Painter said the eastbound side of I-20 was temporarily closed down, so a Lifesaver helicopter could land on the interstate.
She said the Riverside Volunteer Fire Department and RPS Ambulance responded to the accident.
Painter said a police officer from the Riverside Police Department was the first on the scene, and the Pell City Police Department assisted with traffic control.