[sandworm101]

>>Adaptive cruise control I mostly trust. It keeps a set distance behind a car,

Sounds like you are also trusting that car. Would this system follow a car into a dangerous situation? I ran into this sometimes while riding sportbikes. Some car would be following us on a strait, a passing lane, but come the first turn it was way out of its league. I saw more than a couple sliding sideways in my mirror.

This doesn't have to involve speeding. On a mountain highway (BC) fast straits often end in very tight corners. The speed limit doesn't change. Braking, merging and cornering all have to happen simultaneously. Leading bikes in a group will sometimes even accelerate into corners to create space for those behind to maneuver. Any car setting its speed according to the bikes ahead of it is in for a nasty surprise.

[stephengillie]

> Sounds like you are also trusting that car. Would this system follow a car into a dangerous situation?

This is more true than it can seem at first. For the GP's point, adaptive cruise behind a car slowing to turn can cause unexpected braking and startle drivers.

Adaptive cruise around sharp corners exposes the current limits of self-driving car vision. These systems usually have a cone of vision in front of the car, that only sees stuff moving 25+ mph in the same direction. Once a leading car is too far around a curve, the adaptive cruise can lose track of the leading car and accelerate sharply.

Some adaptive cruise systems intentionally don't accelerate while on curves, likely for this reason.

[magduf]

Something like this happened to me not long ago, but in my car (a good-handling economy car (Mazda)): some asshole in a big Mercedes SUV was tailgating me very closely, pissed that I wasn't going fast enough for him, and he was unable to get around me on this long exit lane. Well the single lane then turned into a ramp, which I took at a pretty fast speed (for a car), as I usually do, and he almost wrecked because his vehicle couldn't handle the turn.

Later, when I was pulling into a left-turn lane and thought he was gone on his way, this asshole intentionally cut right in front of me.

[alexhutcheson]

I wouldn’t use the adaptive cruise control on a mountain highway, or any other setting with possibly sharp turns where I have to adjust speed up and down. I wouldn’t use normal cruise control in that setting either.

[sandworm101]

But my point still stands. If you are letting the machine set your speed according to the car ahead, what if that car's speed is not appropriate for you? Does the machine make a judgement as to the performance abilities of the car ahead? Humans wouldn't follow as close to a Porsche as they would a truck. You don't want to be too close to something that can stop far faster than you can.

If the adaptive cruise control is staying far enough away that it can always stop that is an entirely different problem. Leaving so much distance, so much empty road, between cars reduces the total carrying capacity of the lane, which isn't good for anyone.