It happened Saturday on Highway 59 near Sandy Mush Road just south of Merced.
Witnesses tell the CHP, a Honda was heading south on Highway 59 when it suddenly veered over the double yellow line and into a semi-truck.
The big rig crushed the car killing the driver.
Now investigators are working to figure out why the Honda swerved into the wrong lane.
"At this juncture we are investigating all aspects of the exact cause. We do know for sure that the Honda was the errant vehicle. It crossed directly over into oncoming traffic," Sergeant. Michael Greene said.
The driver of the car died at the scene.
The semi-truck driver and his passenger were taken to the hospital and treated for minor injuries.