A man driving a Ford F150 pickup crashed into the horse, which was trotting on Camino Tassajara in the dark, said California Highway Patrolman Steve Creel. The driver glimpsed the horse and braked to avoid it - but he was too late.
The accident caused minor to major damages to the driver's truck, which had to be towed away. There were no injuries to the driver.
The area is filled with horse pastures and equestrians, said Creel.
"There are numerous horses," he said, speculating the horse may have wandered out of its pasture.
County maintenance officials showed up at the incident and cleaned the bloody mess, driving the horse carcass away in a truck. The road and traffic were cleared by 7:20 a.m., Creel said.
Creel noted that daylight hours are shorter during the winter and people should be familiar with the roads they travel.
"Just be highly aware," he said. "Know where the animals tend to hang out."
Police said Wednesday morning that Animal Control had contacted someone they believed to be the owner of the horse.