That's not a bad strategy. Driving slowly on slow roads or in adverse conditions and fast on highways seems rational to me. What is the point of making a road that is specifically designed for high speed and then putting a limit on it? The speed limit is an incredibly blunt instrument for deterring bad driving, as if driving below the limit is always going to be the safest option. It also motivates law enforcement abuse. The vehicle-environment-driver complex is much more nuanced than a single variable threshold.

They don't do it because the U.S. has good standards for what is a crime.

For example cops can't tailgate you then give you a ticket for speeding.

Additionally, doing this only on freeways would probably make the roads less safe as drivers would go faster on surface streets. Thr 65mph speed limit was set in the 1950s by 1950s white men for 1950s cars. Freeways are safer than surface streets by multiple factors of 10.

Another factor that hasn't been mentioned yet is it gives cops pretty unilateral right to pull you over if they feel like it. IANAL, but in many places it's illegal for a cop to pull you over just for "being suspicious", but because of speeding and various other traffic laws on the books that are almost universally ignored, they can pull you over for speeding, then decide you seem suspicious and search your car, breathalyze you, etc.

There's lots and lots of laws like that

Like perjury. It's almost never pursued, the judge will just order your testimony ignored

Or paying your taxes. You're basically expected to do your best to cheat, especially if you're a corporation

The other aspect is that we typically are against automated enforcement regardless of the law.

We typically want people to be in the loop. If there were more visible traffic cops, people tend to slow down to the limit.

If that happened people would avoid toll roads which means there won't be enough toll income.

Cars might have gotten better, but a lot of highways haven't been improved enough for those higher speeds. For example, there's a lot of on ramps in older cities with very short merge zones, and you need to hammer the throttle and pray that there's a spot for you by the time you hit the end.

This is especially true if the person in front of you refuses to accelerate to highway speeds to merge safely, simply hoping that people will be nice enough to let them in.

There's one near me where I've almost been in accidents just about every time I use it.

I’ve had people blow past me at like 20-30 over. Swerving all over through traffic. Only for me to pull up beside them at the stop light at the top of the exit ramp. Worth it. Not saying it’s always the case. But it’s funny af when it does.

Can you tell these stories? I didn't think cops would pull you over for going the speed limit in the right lane.

“why was this neighbourhood road designed like a freeway”

The stroad by my house is five lanes wide with a 45mph speed limit but still has crosswalks that nobody can use because it's a five lane road with people doing 45mph and many people have already been killed crossing. So many that children are bussed from the school across the road because it's too dangerous to even have a crossing guard.

You read that right: Kids who live less than 200 feet from the school can't walk there because the road is too dangerous.

And we can't get the speed limit lowered because it's a state highway and the state says it has to be 45 and the local community has no say in it.

And people wonder why I hate authority.