One way or another highways have portions where there has to be a solid, flat, vertical surface on the edges of barriers, exit ramps, etc. It's similar in many ways to the hairy ball theorem.
You can't just round over the edge of the barrier, because that still leaves a portion where a car could collide perpendicular to it. You can't just slope it down to the ground, unless you want an impromptu Dukes of Hazzard reenactment. You can't have just an unguarded edge because that would just be a death sentence if you hit it at any appreciable speed. The solution is to place those crash attenuators so that it slows the vehicle down over a small distance rather than just over the length of the crush portion of the car.
https://en.wikipedia.org/wiki/Hairy_ball_theorem
You can't just round over the edge of the barrier, because that still leaves a portion where a car could collide perpendicular to it. You can't just slope it down to the ground, unless you want an impromptu Dukes of Hazzard reenactment. You can't have just an unguarded edge because that would just be a death sentence if you hit it at any appreciable speed. The solution is to place those crash attenuators so that it slows the vehicle down over a small distance rather than just over the length of the crush portion of the car.
https://megarentalsinc.com/sites/default/files/feature-image...