Hacker News Reader

Comment by randlet | Hacker News Reader

> Imagine someone added Adaptive Cruise Control to your existing car without telling you - the first time the car braked on its own, you’d freak out. The car is suddenly behaving in a way it should be able to.

I recently got a hell of a shock in my fathers BMW: I was driving with cruise control engaged, depressed the clutch, and when I released it, found the car re-accelerating to match it's previous speed. Every other car I've driven has disengaged cruise when the clutch is engaged, so this took be quite by surprise and could have put me in danger.

View on HN

Another oddity in using adaptive cruise control that happened with me and scared me a bit: imagine you are in a congestionated area and eventually enter a lower speed uncongestionated area, the car is going to speed up. If you don't notice the speed up and intervene immediately, you might easily end up at speed that is unsafe, unallowed, or both.

Does that mean that if you shift down, the car will still accelerate / maintain speed and that "breaking on the engine" (slowing the car down by increasing the revs and not accelerating) doesn't work?

What gave me a scare was lowering the cruise speed on the steering wheel by clicking the button a few times, which in fact caused the car to actively break quite hard instead of naturally lowering its speed.

EDIT Now that I think about it, my BMW does not disengage the cruise when you shift up and ... I'm not sure if it does when you shift down.

> EDIT Now that I think about it, my BMW does not disengage the cruise when you shift up and ... I'm not sure if it does when you shift down.

My BMWs (E46, E39) all have two clutch switch outputs: one for the starter and one for cruise control.

The cars I've driven only disengage cruise control if you tap the break.

My '97 Mazda, '02 BMW, and '15 Ford all disengage cruise when you clutch. What do you have that doesn't, and are you sure its clutch safety switch is actually working?

>are you sure its clutch safety switch is actually working?

If the clutch switch was inoperative and the cruise control was engaged, the cruise would not know the engine is disengaged from the transmission and would rev the engine up to redline.

Reply on news.ycombinator.com