The solution is not to have laws dictating that people drive slower, but to engineer roads so that people naturally drive slower. Add some curves to roads. Add speed bumps in all residential streets and parking lots. Make roads narrower. Add more stop signs or traffic lights.
Curves to slow down? Sorry but a bunch of curves don't make you drive slower than the 100km/h / 65mph / 70mph speed limit. Germany's Autobahn has many many curves and many of those have no speed limit and you can take them easily at 150+ km/h. Seriously, buy a plane ticket and try it for yourself. It's awesome.
Stop signs are aggravating if people had to actually stop 'properly' at every single one. No wonder people do a rolling stop most of the time. Many European countries do this the right way and do not have stop signs everywhere but instead have the main road have right of way or rules. To bring up Germany as an example again: in many places where we need stops signs all around, they simply have a rule that says the person to the right is allowed to drive first.
Speed bumps do nothing, except very very locally. You can't have enough of them to actually slow down cars along any reasonably long stretch of road and adding so many that it would will get the locals to NIMBY them into oblivion. I can almost guarantee that. Like put two or three in front of that school, sure. Plaster the entire neighborhood with them? Forget it.
I'm not arguing that street design can't affect how fast people drive.
I'm saying "some curves" like the parent said won't do that magically all by itself.
And yes, I am very much arguing that putting a speed bump at the beginning of a 1 mile road will not do anything for at least 0.9 miles of that road. That's my point about "very locally". Anyone that argues differently I would call weird.
It's also funny how many things are super local. We already see people here argue about 85 or 90 with regards to Texas roads. Here in my neck of the woods they actually are gonna go from 100 to 110 km/h in some places and the radio was arguing how they can't imagine going that fast etc. Well guess what, the Autobahn is full of people going ~140 km/h (which is right smack middle between 85 and 90 mph actually) and it's absolutely normal and fine and if you go 140 and stay on the left lane people will honk at you to let them pass. One thing that comes with the Autobahn is that you always have to drive on the right-most lane available and no passing on the right is allowed. That would be insane at the allowed speeds (which in many places is unlimited).
Road traffic fatalities 2020:
Canada 1,745 for ~35 million people
Germany 2,562 for ~85 million people
US 39,007 for ~332 million people
Looks like Germany, with its unlimited speeds and no 4-way stop in sight is at ~30 deaths per million, while here it's ~50 and the US is at a whopping 117.5.
Having driven the autobahn, my theory is nobody has time to die - just a moment and they're already at their destination.
That said, I think the autobahn has pretty good engineering. None of the potholes and ripped up roads from road crews.
And none of the entitlement.
If two people want to speed, one going 70 in a 65, and one wanting to go 90 in a 65, they both are annoyed because they feel entitled to go that speed.
On the autobahn, if someone wants to go faster than you, he is allowed so you have to get out of the way, that's the rule.
I think the curves are actually part of it. But the other way around. The Autobahn in most places actually on purpose follows the landscape and has lots of curves going left and right. Not to slow people down but to keep people 'awake'.
Nothing is more boring than going in a straight line for 8 hours at a fixed 100km/h / 65 mph. The closest I personally have been to a traffic fatality was in Florida doing exactly this. So effing boring!
The most alert I have been is on the Autobahn going anywhere between 100km/h and 180km/h up and down through the hills around Kassel, going left and right. Having to slow down because someone is going "only 140km/h" on the left lane in front of you. Speeding back up. Going in a nice "tight" right turn up the hill while flooring it in 6th gear.