It's been shown that if you redesign the street, you can change human behavior on that street including lowering the average speed that drivers choose to drive at.
Designing a wide-open 4 lane boulevard then slapping a 30 mph speed limit on it is a terrible plan, yet how often we do exactly that in our cities.
Look up "traffic calming". There are plenty of well-studied techniques for discouraging excessive speed that don't involve terrifying the drivers or limiting visibility, and make things safer for pretty much everybody involved.
It's ironic that it's called traffic calming, because the effect of adding chicanes and speed bumps and similar things is often to make drivers annoyed or angry.
Ultimately though, it does result in the desired reduction in speed. So yes, it works.
Narrow streets without road markings is what we generally do to slow traffic here in Europe. They are safer and slower without the need for speed bumps. We have full sections of the city centre without markings under free-for-all and pedestrians can freely walk on the street. Less crashes and safer strees.
No need to make them poor visibility tho. That would be just stupid.
If they consistently got a ticket for exceeding the number on the sign, I'm betting people would suddenly feel a lot less comfortable at higher speeds regardless of what the road looks like.
The reason people drive as fast as they feel comfortable is that speed limits are seldom and inconsistently enforced, so people are more restricted by their own notion of safety than the risk of any legal consequences.
This is (mostly) correct as any country with a significant Gatso camera presence will attest. In the UK people more or less drive exactly at the speed limit at all times because of the profusion of speed cameras and heavy penalties for speeding. (Up to and including a lifetime ban from driving)
While true, this feels like a tangent. In this case, "cars following the speed limit" serve the same traffic-calming purpose as the urban planning choices you're describing.
Sure, if you can't pass and there's someone in front of you going slow, it will force you to slow down.
Most injuries and deaths by car in SF are of people outside of cars, and I suspect that the drivers who maimed/killed those people were usually in front / catching up, not following someone at high speed and had their victim jump between.
