Coming back from Kentucky yesterday, Belle and I were almost home. Traveling westbound on LA Highway 28, we were scent miles from home and starting to relax a bit. It was dusk, and we had made good time. Belle was driving, the posted speed limit set at 55 mph, and Belle had the cruise set at 58.
An 18-wheeler came up up behind us and started to pass. Good road, plenty of room, and the driver gave us a friendly toot on his horn as he came around. Not a blast, nor a blare, just a friendly little toot.
Belle was a bit nonplussed. "What is he blowing his horn about?"
I turned to look at the truck. "Well, he knows the law."
Belle glanced at me sideways. "I have never blown the horn when I was passing."
I modified my statement, gently. "The law might have changed since I enforced it. But, it's required when passing on a two lane road."
We got home safely and went to bed, but over coffee this morning, I fired up the intertubes and checked. Sure enough, there it is.
(2) Except when overtaking and passing on the right is permitted, the driver of an overtaken vehicle shall give way to the right in favor of the overtaking vehicle on audible signal, and shall not increase the speed of his vehicle until completely passed by the overtaking vehicle.
The law requires that when passing on the right is not allowed, a vehicle overtaking another must provide an audible signal to alert the vehicle being overtaken. This law was passed in 1962 and has not been repealed.
Now you know the law, and so does Belle, who is quite amused that she has been in violation for her entire driving history.