On Tue, 01 Sep 2009 05:36:02 -0700, Auto Tech wrote:
If it doesn't have a date and information on the periodical it was
originally published in then it's a rumor, and not something you should
give much weight to. _Any_ unattributed email or news posting should
bring the needle of your BS-O-meter well off of zero.
And if the car is "hydroplaning" it can't have "literally flew through
the air" -- the two are mutually exclusive, for a variety of reasons.
Given that, This statement should bring the needle of your BS-O-meter
pretty close to the peg.
So why are you forwarding material that pegs the needle of your BS-O-
meter? Or, if your BS-O-meter needs a new battery, why are you
forwarding material at all?
_Any_ closed-loop feedback control system has a process variable that the
designer _really_ wants to control, a measurement of the process variable
that the controller can see, and a command variable that the controller
actually pushes around. In the case of cruise control the process
variable is the speed, the command variable is (directly or indirectly)
the throttle setting, and the measurement of speed could be taken from a
variety of sources.
A cruise control that regulates the speed of the car by sensing the speed
of the driven wheels won't run away like that, although it may surge to
an astonishing degree if the wheels lose enough traction. The reason is
because the measured speed is the driven wheel speed; if the car was
going to go faster than the wheel speed then you're in deep **** anyway.
The only way that a closed-loop system could run away as described would
be if the system is sensing the speed of the non-driven wheels, _and_ if
those non-driven wheels are going slower than the actual speed of the car
-- then the controller will 'try' to increase the speed of the car even
though it's already correct.
What _is_ sensible is that in slippery conditions you shouldn't be
driving at a constant speed! If you start to hydroplane and you're the
least bit sensible you take your foot OFF the gas, GENTLY, and let the
car slow down. Cruise control won't do this -- it'll maintain speed like
it's designed. That's not "running away", but it's certainly going much
faster than it should be, and would seem like running away to someone who
slows down on slippery roads without really thinking about it.
So don't forward any more BS, but don't trust your car to drive for you
in the rain and snow.
Which forum is that?
Last week a CHP officer, off duty and driving a loaner Lexus, was
killed along with others of his family. Early reports were that the
driver could not control the speed of the car. Someone actually called
911 from the speeding vehicle just before the crash.
I never paid much attention to cruise control, even though I had two
cars with the option. Then it became something of a habit, in my most
recent three cars. It still scares me, but I use it only in fair
weather, on long, uninterrupted stretches, with little traffic. And it
still scares me.
Nice motive for the original post. My view, you ought to take it for
what it was: a warning to be careful who and what you depend on. Try
not to be so technically literal. Find the value, and say "Thanks",
offer a careful, thoughtful, calm suggestion if you have one.
The forum that you are reading right now. That is what these newsgroups
He was not out of line.
This was crossposted to a number of newsgroups, all of them having to do
automobiles and driving. There is nothing wrong with that either.
If you dont like it, dont read it.
Oops. Quite a challenge, there, liking or not liking before reading.
I was just interested in knowing which of the newsgroups the post was
If you don't have a civil answer to a straightforward question, don't
respond to it.
Oh it did. This has been floating around for years. Someone sent it to
me yet again recently and I've been debating them over the merits of
what strikes me as cartoon physics and auto-tech issues within the
story that ignore certain realities of how CC generally works, what
the overall road environment is likely to be if hydroplaning or
slipping on ice is an issue. I decided to post it in some auto forums
to see what kinds of feedback it inspired so this other party would
see that it's not just me that sees a degree of b.s. in it.
My position is that the primary problem isn't cruise control but not
adjusting for diminished conditions. If you're hydroplaning you're
going too fast. You lose a small amount of time to decel with the
cruise on that would otherwise happen as soon as your foot comes off
the gas but you should have been slowed to begin with. The story
demonizes CC without really addressing the fundamental issue, and
actually obscuring it. The story indicates she was driving at a "safe
speed" but apparently not.
On Tue, 01 Sep 2009 13:00:08 -0700, Auto Tech wrote:
It sounds like something that would come up in Reader's Digest.
I didn't see the original publication info in your post, so I assumed you
just got it anonymously.
I think we agree on that point, then. The problem with cruise control
isn't what it does to the car, the problem is that it takes away the
deadman switch, and lets the car go full speed while the driver's
attention wanders. About the only time I use it is when I'm on flat
empty road and I'm constantly exceeding my comfortable speed (and I'm
driving someone else's car) -- then I'll use it just to keep me from a
If you can't maintain your attention while using CC, then you
shouldn't be driving at all. CC is a valuable tool, gets better
mileage than you do and maintains a set speed far better than any
'manual' driver. Nothing is more annoying than following someone down
the road who is not maintaining a set speed.
It can be termed running away. This just happened to me a couple of
years ago. I never gave a thought about using cruise control on wet
pavement until my blazer did go out of control.
I was just cruising along at 50mph down the right hand lane of a five
lane highway. Puddles were forming in the right hand lane. Evidently I
started to hydroplane. The truck slowed and turned slightly sideways.
The wheel speed seemed to increase also.
After passing through the puddle the combination of a slightly
sideways truck and over speeding tires took hold of the road, but not
evenly. One rear tire seemed to grab the road and send the truck into
an immediate turn. I tried to correct, but with the cruise control in
charge of the accelerator and me in charged of trying to straighten
the truck out it became a perpetual right/left, right/ left over
correction fight between me and the cruise.
I only gained control by quickly shutting the cruise down. Once done
the perpetual right/left, right/left could be stopped.
Interesting, dramatic story. You mean during all the time you were fighting
off the instability-right/left etc- you never tapped the brakes? Would have
been a lot faster and simpler than playing around with the cruise control
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