A man who crashed on Highway 101 Wednesday afternoon near Windsor and died may have had a medical emergency before losing control of the car, the CHP said.
Police did not immediately identify the 55-year-old Santa Rosa resident, pending notification of relatives.
Witnesses said the driver hit cement barriers with his Dodge pickup before the truck ran off the Central Windsor offramp, CHP Officer Jon Sloat said.
The truck then ran through a fence and stopped in a field.
Emergency responders performed CPR but could not revive the driver.
The CHP closed the offramp after the 1:30 p.m crash, causing a significant traffic back up on the highway.