The woman was driving a 1989 Toyota Corolla in the eastbound lanes near West Main Street about 7:20 a.m., turned the vehicle abruptly to the left and crashed into the center divider, according to California Highway Patrol Officer Kevin Pearlstein.
The driver was not wearing a seatbelt and was partially ejected through the windshield, Pearlstein said.
She was taken to Sharp Memorial Hospital, but died of her injuries, he said.
The wrecked car came to a rest blocking two lanes, which left traffic backed up to Grossmont Boulevard, according to Caltrans. A SigAlert was issued, but all lanes were reported as clear shortly before 9 a.m.