The problem is that such a limit would not be a safe one, you would basically be replacing the limit with a sign that posts the rate that people like to drive at.
Turns out that people do drive at a reasonably safe speed, generally.
Source: https://jalopnik.com/utah-raises-some-speed-limits-to-80-mph...
According to who? The minority who wants the limit set elsewhere. Things like "what speed is safe and reasonable" are matters of social consensus. The "experts" can pontificate all they want and the vocal minority can gripe all they want but the median or average person and society at large is always going to be right on matters of social consensus. It's a tautology.
The main safety increase I can see is with respect to commercial trucking. Not all vehicles have the same acceleration and braking ability. But the fact that people just ignore the speed limit is a hard problem.
So, yes, as far as is practical, that's the idea. We just post the speed people are driving at.
Reasonable drivers conform their driving habits to the environment.
Unreasonable drivers should not be allowed to drive.
> [Wiki] Traffic calming can include the following engineering measures ... Narrowing traffic lanes ... Converting one-way streets into two-way streets forces opposing traffic into close proximity, which requires more careful driving
What is happening here? Did the engineers forget that they were supposed to optimize for safety, and instead optimized for getting people to slow down? Does the net effect of this improve safety, or worsen it?
If everyone drives as fast as they can while meeting some perceived safety level, then does that mean these efforts are unlikely to affect safety and merely to slow everyone down? Is the best set of measures the maximally deceptive set, which looks as dangerous as possible while being as safe as possible?
No. It means that people are usually wrong when they judge the safety level of their driving speed on a nice clear road that happens to have pedestrians next to it or trying to cross it, but are more accurate at judging safety when they are primed to expect obstacles, steering challenges, other actors moving not in parallel with them on the road itself.
My understanding is that speed limits have been largely unchanged for the past 50+ years. Car safety, on the other hand, has increased by a great deal.
It seems likely to me that speed limits are conservative when it comes to safety.
I don't know exactly how it goes. If it's chosen (or heavily influenced) by politicians, I suspect politicians can win some votes by saying they'll improve safety by lowering speed limits (particularly around schools or other places where children might be); while they'd be less likely to win as many votes by saying they'll raise the limits (exposing them to the risk of their opponents calling them reckless/irresponsible). If it's chosen by non-elected officials, that's less of an issue, but something like it may still be there; or it may be that raising the limit and then there being a fatal accident will damage your career, while lowering the limit and irritating everyone will not damage your career.
I've driven on many roads in countries that don't have any speed limits. The overwhelming majority are driving a speed that makes sense given the road, driving conditions, etc.