> Note there is a concept traffic engineers use called "the 85th percentile rule" that helps design highways by setting the speed limit for maximum compliance. Using this rule leads to the safest roads.
The fundamental flaw in this concept is that it completely ignores that 1) the ideal speed depends on external circumstances and intended road use, and that 2) road design heavily influences driving speed. If you want to have a safe road network, you have to design it for a specific speed. When done properly, drivers will naturally be driving at the intended speed. Speeding doesn't happen because it doesn't feel safe to speed.
Highways have to be straight and wide, without any level crossings. People are supposed to drive at high speeds, so it is designed in such a way that it is safe to do so, and it feels safe to do so. Local access roads are narrow, twisty, have relatively poor visibility, and are equipped with things like speed bumps. You're supposed to drive at slow speeds because there are lots of level crossings and driveways, so they are intentionally designed to make high-speed driving unsafe to the point of being physically impossible.
The fundamental flaw in this concept is that it completely ignores that 1) the ideal speed depends on external circumstances and intended road use, and that 2) road design heavily influences driving speed. If you want to have a safe road network, you have to design it for a specific speed. When done properly, drivers will naturally be driving at the intended speed. Speeding doesn't happen because it doesn't feel safe to speed.
Highways have to be straight and wide, without any level crossings. People are supposed to drive at high speeds, so it is designed in such a way that it is safe to do so, and it feels safe to do so. Local access roads are narrow, twisty, have relatively poor visibility, and are equipped with things like speed bumps. You're supposed to drive at slow speeds because there are lots of level crossings and driveways, so they are intentionally designed to make high-speed driving unsafe to the point of being physically impossible.