Hello,
On past tours, I rode many perfectly straight roads located several light years from nowhere that had almost no traffic. I could see many miles in either direction. On these roads, cars would of course approach me from behind. Because the road was straight with no stops, no other traffic, and no buildings or turnouts of any kind, I always assumed that the drivers of these cars are probably somewhat zoned out. They don't really have to concentrate, as all they have to do is keep the car pointed straight. Plus, in high-heat, things ahead of them may kind of waver or appear out of focus as the heat bears down from the sun and drifts up from the roadway.
Are they paying attention enough to truly see me in the road after being "relaxed" for such a long period of time? Worse, are they also babbling on the cell phone, oblivious to little else along their journey?
To help them along and also protect myself, I literally signal to them that I AM HERE, up ahead of them. To do this, I simply arc far out into the road and back to the shoulder, and then repeat the process. My movement almost surely catches their eye, and I feel a bit safer.
David in PA (now in FL)