Sure, but a lot more crashes are caused by poor design (including design that facilititates law-breaking) than mechanical failures or lack of enforcement.
In particular, I want to address the latter: trying to stop people from speeding by having more police patrols simply doesn't work. The only thing that does work is physically changing the design of the street (narrowing lanes, etc.) to make it scarier and less comfortable for drivers to go too fast. That's the engineers' responsibility, not law enforcement's.
Not on freeways, no. The design principles appropriate for freeways are entirely different than the ones appropriate for city streets. It's the latter where I suspect most of these Waze "dangerous hotspots" will be, and so it's the latter that I had in mind when writing my previous comment.
I travel some pretty narrow streets (one car width) in Portland and that doesn't seem to stop people from breaking the basic rule. I don't think most drivers are even paying attention to anything other than their next fancy ice cream cone or fancy donut.
Could you point out an example on Google Maps? Maybe there's something else wrong with it.
Also, instead of focusing on there still being some speeding despite the street being narrow, consider how much worse the speeding might be if it weren't.
Seriously - the most dangerous roads I've ever been on were in Texas where there were 12 lane highways, and crazy people who wanted to drive 100MPH past you in the right-hand lane, all while people are merging on and off the highway.
Doing the speed limit meant that EVERYONE was driving faster than you, which meant that you were a lot more likely to get rear-ended from someone who didn't see you in time. You have to speed to stay safe, and then you add in construction zones and it's just a death trap.