Mr Red said: "Now what do you do with tailgaters and someone squeezing in - into the (un)safe margin you have manufactured."

Then leenia said: "
The two-lane highway, on the other hand, is known as the killer highway."

The scariest thing I ever saw was many years ago when a friend & I were driving across Montana, USA. We were crossing very wide valley where they had constructed a "cut & fill" 2 lane highway. It was maybe 3 miles of a very tall upside-down V with a road on top. There was a long string of cars going West..... I was in about the middle of the line, leaving about 2-3 car lengths behind the one ahead ..while 'most' of the cars were bunched up to just over one car length..(we were only going 45-50 MPH on that scary stretch- no guard rails and a LONG way down).
I happened to glance in the outside rear view mirror, and to my horror saw a car WAY back at the end of the line pull out and come barreling down the line of cars! He must have been going 85-90 MPH! I glanced ahead and saw several cars coming the OTHER way appear in the distance. Before I could yell "Oh, NO!" this idiot passed me, hit his brakes, slipped into the barely sufficient space in front of me just as the 3 cars (probably scared to death) passed going the other way! Then he pulled out again and accelerated back up to 80-90 again, passed a dozen more cars, and disappeared into the distance.
   If I had been as close to the car in front as most of the others were, something terrible would have happened. I'd like to think the idiot would have just driven off the edge... but he probably would have forced me or someone near me off instead...or just braked and hit the oncoming cars head-on.
   No, I didn't think to get a tag number.