I'd thought of this before, and I remembered it as I drove down I-5 from Bakersfield. There was an accident last October that closed the Newhall Pass interchange. So I deliberately took the southbound truck bypass through the tunnel where it happened, and tried to imagine the collision that happened there. It wasn't hard; I was in the only passenger car, boxed in by tractor-trailers, all of us rolling along at highway speed. It's downhill, and the approach has a slight left turn. Somebody makes a mistake, and there's a very big problem. That night, someone did, and three people died.
I spent some time afterwards on the drive into Los Angeles thinking about the dead. In America, forty to fifty thousand people have died every year on the roads for as long as I've been alive. The cumulative number as of 2003 is over three million, according to this saferoads.org pdf. The DoT says there's only a little over four million miles of road in the US, so there's a death for every mile and a third, obviously not particularly evenly distributed.
Maybe if we really thought about it, it'd be harder to keep driving. But if you believe in haunted places: the roads are full of sudden, violent death, so why shouldn't they be full of ghosts?