The crash was reported shortly after 3:50 p.m. on eastbound Highway 80 east of Carlson Road, CHP Officer Kevin Kroncke said.
A black vehicle apparently spun out and hit a pole on the right hand shoulder on the highway, Kroncke said.
Authorities briefly closed Highway 80 in both directions while a medical helicopter landed on the highway. However, the victim was pronounced dead at the scene of the crash so a medical evacuation was not attempted, according to Kroncke.
The helicopter has since left the highway, he said. All westbound lanes have reopened, while all but the far right eastbound lane were also reopened as of 4:35 p.m.
The vehicle was "pretty badly mangled" in the crash, CHP Officer Sam Morgan said.
Morgan said authorities are investigating why the vehicle spun out, and believe it may have been cut off by another vehicle, Morgan said.
The far right eastbound lane is expected to be closed into the evening because officials from the coroner's office have to drive out from Martinez to the crash scene during peak commute hours, he said.
Morgan recommended that drivers find other modes of transportation or other routes than eastbound Highway 80 during the evening commute.