Did James M. Cain visit this specific area? Later in the book, the name of the road is supposedly Malibu Lake Road--a place which may have existed then but doesn't now.
Frank says there were two roads following the coast: they took the one 10 miles inland. We've determined that this was likely the 101, which parallels the PCH and intersects it in Ventura, as described by Frank on page 41. Past Malibu Lake, as described in the novel, there are several mountainous roads leading towards the beach, any of which could have been the site of the murder. Cora turned here under the guise of seeing "where the movie stars live". But as Frank says, "The real idea was that this connection is about the worst piece of road in Los Angeles county, and an accident there wouldn't surprise anybody, not even a cop." (pg. 41)
"He got in, but shoved his face out to the window and let go one. I braced my feet, and while he still had his chin on the window sill I brought down the wrench. his head cracked, and I felt it crush. He crumpled up and curled on the seat like a cat on a sofa. It seemed a year before he was still. Then Cora, she gave a funny kind of gulp that ended in a moan. Because here came the echo of his voice. It took the high note, like he did, and swelled, and stopped, and waited." (pg. 43)