Seems incredibly dangerous. Imagine some bad GPS reading warps you from a highway to a school dropoff zone and decelerates you to 20mph
The fine details of implementation are not noted so we can only speculate. I would hope it's designed to very gradually start limiting the speed after X seconds of alerting the driver. That said, even the most naive design, which would work the same as RPM limiters (which all cars have to avoid engine damage) would just cut fuel injection whenever over the limit. This produces about the same effect as coasting in neutral, so even then you are going to coast to a stop very very gradually and have lots of time to make it to a shoulder.
That said, even that does present some danger -- not to me or you of course, but you know, to shitty drivers who might not be accustomed to driving cars that fail at random and might panic and fail to cope appropriately with the situation. I mean, I have even ridden with drivers who are afraid to stop on the shoulder, even in a situation that warranted it, so it's bound to happen now and then. A manual override if available, will help here, but the pool of drivers dumb enough to still be startled into making a mistake will merely shrink then, not disappear.
Now queue this. This has the potential to really go incredibly wrong. You mention shoddy drivers for who it can be pretty unsafe. Even if there's only a tiny percentage of drivers out there that is shoddy, multiplied by the number of drivers, it's still a lot. And I would argue that the percentage of shoddy drivers is actually not such a tiny percentage but a larger one.
This has to be automatically overridable. I.e. by simply hitting the gas pedal. It can't be something special you need to do. If there's a dangerous situation on the road that can only be avoided by speeding up beyond the speed limit, I don't have time to remember where that extra special button is that I almost never use. I need to be able to just hit the gas pedal. If you're wondering what situation that might be, there's actually such a situation that I remember from my driver's license test. Basically something unforeseen happens (don't remember the specific, but let's say a car shoots out of a hidden driveways or something) and you have no space on the left or right (let's say a bunch of trees, houses etc.) so you can't just go there. You don't have enough space to stop the car before hitting that car, so hitting the brakes is out of the question. You have oncoming traffic on the other lane as well but that car is still far enough away that if you shift down one gear and hit the gas pedal, you can swerve around the unforeseen obstacle without crashing head-on with the oncoming traffic on the other lane. I need one hand to shift, the other to steer and those two things already take all of my concentration not to mention the split second decision to see that braking will cause a crash while speeding up will save the day.
Nice "trick question" though :)
I do disagree with your justifications though. To start with for indicators it is true that sometimes they aren't necessary, in fact with everyone driving appropriately they shouldn't ever be needed to avoid crashes. However people are pretty bad at judging their abilities and habits are a pretty strong effect. So sometimes you mess up your observations but then if you indicate anyway the other road users are more able to fix your mistake. Also by indicating every time you build the habit and are much less likely to forget to indicate when you should.
It is fun trying to come up with situations where speeding up to avoid a collision is needed but in practice this is really dangerous. If you brake to avoid a collision then if the avoidance fails the result is less bad. Any cases where braking isn't going to let you avoid a collision must be situations where you have very little time to react since cars can change speed more rapidly by braking (limited by traction in any vaguely modern car). So the situations where you need to speed to avoid a collision are ones with very little time to process, where you have one known bad road user (since otherwise you wouldn't be at risk of a collision). Bad road users are unpredictable. All these factors make it really dangerous to accelerate into a hazardous situation. Instead you should train yourself to drive defensively and react to road dangers by braking as a first response. Again it is best to build a habit since you have very little time to evaluate and react to these situations.
I agree with you about the shoddy drivers, I don't drive a large amount so I'm aware that my driving skills aren't super high. Because of this I consciously drive defensively, don't drive fast to give more reaction time, leave a larger gap to other vehicles. Having lots of shoddy drivers is a great reason to have speed limiting technology because most of them overestimate their skill and speed. In the UK a large majority of drivers regularly speed and this has a pretty direct link to increased injuries and deaths.
I have actually been in situations where swerving around an obstacle that appeared suddenly was the best option more than once. If I had hit the brakes, someone could have been seriously hurt (not just talking about making metal and plastic trash out of a car) - sometimes that someone being me, by being squished by something much larger, heavier and better built than my car's tiny crumple zone. Think huge - probably full of heavy stuff too - truck trailer coming at me with its broad side. If I had hit the brakes instead of speeding around it, I would not be writing this.
In such a situation you do not have time to think about a button you have to press to disable some "please adhere to the speed limit" software. You ideally want to be in an automatic transmission car where you can just floor the pedal and it makes a jump, unless you're a able to shift down quickly like a race car driver and floor it. I guess my point is that these system really do need to take into account the worst case you can imagine and make that worst case safe.
It's a nice idea, but the tech really isn't there yet. I guess a few high profile incidents and they'll be forced to fix it.
That alone probably makes it a nonstarter in the USA, right?
And it's not a lot. Being caught a bit over 3 times will lose you a licence, or 2 if you're a new driver. Sometimes you can get an awareness course and get a "pass" on the first time but I think only once every few years. Exceed the limit by too much and you don't get that option and you also get more points. You also will find insurance punishingly expensive for years afterwards.
On autopilot they do periodically do absolutely insane stuff like this due to bad map data, gps drift, lack of recent speed sign reading etc
And they are supposed to be best in class