Because a " slow moving vehicle " triangle is not legal in all 50 states for this purpose the RV bumper could display the DOT approved reflective tape instead .
The kind that is 2 inch wide and has alternating red and white reflective segments that is now found on every commercial trailer .
Because I tow a 21 foot trailer with a turbo diesel pickup I rarely impede traffic .
But on many trips that will occur .
If I have a car behind me when I get to a straight where I can see that there is plenty of room in the oncoming lane to pass I will pull over a foot or two to the right and slow down so that the vehicle(s)can get around me easily .
This is a condition of living near 2 lane US Highways .
Freeway drivers may not have had this frequent issue and are not conditioned to this practice .
Fulltime 2 lane US Highway drivers can be spotted for another practice especially in winter .
They always give extra car lengths when following another truck than the freeway driver crowd .
On a 2 lane highway you have nowhere to go but the ditch if the truck you are following too close slams on his brakes to avoid a deer .