The incident was reported about 11:45 p.m. on Highway 154 near Paradise Road at the upper end of the Santa Ynez Valley, the CHP said.
They were declared dead at the scene, and their names were being withheld pending notification of relatives.
“For unknown reasons, the pedestrians had exited their vehicle, which was parked on the right shoulder, and entered the traffic lanes,” the CHP said.
One of the victims apparently was struck by an eastbound Toyota Yaris driven by Karen Gong, 45, of Oak View, the CHP said.
The other victim apparently was struck by a westbound Ford E-250 van driven by Martin Macarena, 48, of San Luis Obispo, the CHP said.
Witnesses at the scene told investigators the second victim may have been struck by a number of westbound vehicles, the CHP said.
Macarena was later located at the Chumash Casino in Santa Ynez, and was arrested on suspicion of felony hit and run causing injuries, the CHP said.
Gong and a third driver, Ma Guadalupe, 41 of Oxnard, stopped immediately at the scene, the CHP said. They were not cited.
Alcohol and drugs do not appear to be factors in this accident, the CHP said.
Eastbound traffic on Highway 154 was blocked at Highway 246, and westbound traffic was shut down on the Santa Barbara side of San Marcos Pass while emergency personnel investigated the accident.
The closure of the highway lasted nearly four hours.
Anyone with information about this accident was being asked to contact the CHP dispatch center in San Luis Obispo at 805.593.3333.