There is a practice on the highways in Texas that I haven’t run into anywhere else. On 2 lane highways, if a car is traveling slower than the traffic behind him, he/she is expected to move over and drive on the shoulder.
In the same vein, oncoming traffic seeing this take place are also expected to move over on the shoulder and allow the passing vehicle plenty of room. In effect, you end up with a three lane highway.
It takes a lot of trust to accept that everyone is aware of these unwritten rules. I’m pretty good with the moving over part but I’m still leery about passing someone when traffic is coming towards me.