The two right lanes of southbound Highway 280 were reopened at about 9:30 a.m.
The woman killed was identified as Amanda Vente, 39, of San Jose, according to the Santa Clara County medical examiner's office.
The CHP received a report at about 3:15 a.m. of a person down on southbound Highway 280, Sarabia said.
Officers who arrived on the scene discovered the woman's body lying in the roadway and said she appeared to have been struck by a vehicle, Sarabia said.
Paramedics from the San Jose Fire Department pronounced her dead at 3:31 a.m., he said.
The drivers of multiple vehicles stopped to try to help the woman, but the car that struck her has not been found, according to the CHP.