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One of the common early complaints about the Prius was that if
the car's speed dropped below 25 or so, the last recorded set
speed in the cruise control was dropped so "resume" would not
work once the car got moving again. Does this imply that the
speed *is* saved in other cars, such that "resume" could work
just about any time and begin accelerating the car again?
.
If so, consider this: many of the complaints in the NHTSA
database [and indeed scattered throughout the examples pulled
and reprinted in the Safetyresearch report (http://www.safetyresearch.net/Library/ToyotaSUA020510FINAL.pdf)] describe unintended
acceleration beginning during a LEFT TURN. It should be obvious
what I'm thinking here, but if not: where's the cruise control
stalk usually located? Right side of the steering column or the
right side of the wheel itself. Which direction is the "resume"
command usually in? Up, or counterclockwise around the axis of
the steering column. What do a lot of people do when turning
left, especially if they're driving automatics? Since their
right hands aren't busy with shifting, they often grab the wheel
low and to the right and swing the fist over the top toward the
left. And given the way most people drive, with a fairly abrupt
and badly-controlled motion.
.
I rarely use cruise-control and haven't been through that many
different cars over time, and would thus like to draw on this
community's collecive experience and/or the desire to experiment,
and propose that in some other modern cruise-control implementations
[particularly those done in software, where electronic throttles are
in use], differently-lax "resume speed" criteria could be a likely
factor in these incidents. Toyota or otherwise.
.
_H*

Interesting theory, but all of the CC controls I remember using have been on the left side of the wheel or in the wheel's center. Still a workable theory, but the geometry works differently. If the CC is on the turn signal stalk a driver can brush the resume button accidently (I think I've done this before.)

The only uncontrolled acceleration I ever experienced was due to ice binding on a throttle cable.

That's the same conclusion I got after the claims of Wozniak. I tried our cruise for the first time ever. I had thin driving gloves on and my finger brushed the stalk turning left. Thick fingers could contact it even easier.

If you did accidentally do something with CC, the first tap of the brake should turn it off.

If you did accidentally do something with CC, the first tap of the brake should turn it off.

Good point, but it sounds like a single electrical defect could make the turn signal stalk CC control design a significant hazard.

At some point I stopped using CC on one of my old beaters (Chrysler/Mitsubishi Colt Vista?) because it had intermittent shorts that made the CC's responses to things like the brakes unpredictable.

Interesting theory, but all of the CC controls I remember using have been on the left side of the wheel or in the wheel's center.

I haven't used it much lately, but as I recall the Subaru's cruise control lever is on the right side of the column. It's a bit shorter than the turn signal lever.

The 99 Elantra had the stalk on the left, but had a little slider that increased speed. The 06 Sedona has the controls on the side of the wheel beside the horn. My 93 Accord had them somewhere on the right most stalk. And the 03 Escape also had it on the right hand side, but cannot recall anymore if it was on the wheel...

All that being said, I thought there was a hard limit in most vehicles of between 0-45 in which you could not set cruise? At what speed are most of the complaints coming from? I was under the impression most are in the starting and up MPH range?

I think Hobbit's theory would be plausible if the CC is on (or near) the turn signal stalk because after you complete your turn you might be past the CC cut-off speed when you turn off your blinker and brush the resume button.

It seems like the cut off speed has gotten lower over the past few years, but I haven't really experimented with cruise control at speeds under 45. It'll be something new to play with.

I know my Yaris will set on CC at 25 MPH or a little less, and the resume works as long as the ignition switch hasn't been turned off or the CC switched off at the stalk. It has to be going a bit over 20 MPH, I think about 23, before the CC will turn on or resume.

I hardly ever use cruise (it puts me to sleep) but I seem to recall that on most cars resume WILL remember your last cruise speed as long as you haven't restarted the engine, and I think most cars will resume from just about any speed.

The latter part I'm not so sure about because I've never owned anything but MTs (hitting resume in anything but 5th gear would be pointless) and I never think to try it when I'm driving a rental.

Specific to the Prius... when you turn cruise ON, it lights and indicator on the dash. When you SET, you have no visual indication that it is SET. That irks me. My 93 Honda, and Hyundai/Kia would at least tell you when it's set... I think this is a glaring omission to make.

I believe most of the manuals I have read state that 25mph was the minimum, but I have used them down to about 20mph. However I also find cars, at least the ones I have driven, often overread by up to 5mph around that speed.

The one thing I would like to see for cruise control is a universal system. I believe we have legal requirements for locaiton of turn signal. I'm sure there is some leeway, but generally I have never had to search for a turn signal control which I needed it. Cruise control should be similar as incorrect usage can result in unexpected behavior which can also result in an accident. Perhaps most importanly would be standard indicators. In some vehicles a cruise control light indicates that cruise control is "on" but isn't necessarily set and doing anything. In other it indicates the system is trying to keep a speed. Still others have one color of light for on and and another for set. None that I have even seen indicate what speed the cruise control is set to. Along with making all of that standard across makes of cars, I'd like to see the gas pedal deactive the cruise control just as the brakes do. I know too many people who almost had accidents because they had cruise control on, then they accelerated using the pedal. They forgot about the cruise control and when they let go of the pedal the car started to decelerate, but only to the set point of the cc. After that, the car kept on going until they hit their brakes.

Adapative cruise control is the new risk factor. We have already heard about the stories of people who suddenly accerated after pulling out behind a slow vehicle because they forget their cc was set much higher. These, like all cruise controls, shouldn't ever accerate quickly and perhaps they shouldn't accelerate at all if they have been at a lower speed for a period of time. Instead maybe a little light flash and ding to remind you to reset to a new speed.

Cruise control, especially adaptive cruise control, are fine ideas, but people are just too stupid. Even smart people make dangerous mistakes from time to time. These system need to be as safe as they can be made.

The Prius low-speed cutoff is about 25 mph, and if you drift
below that the remembered "resume" speed is lost. In the FEH
we were playing with yesterday, the low threshold seems to be
about 30 but the "resume" speed is remembered as long as the
ECU still has power, i.e. we could stop, get back up to 30 or
so, and "resume" which would have tried to take us back up to
our old highway speed in the middle of town. Hmm.
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I'm not going after any specific thought or accusation here,
but what we're seeing is that the CC designs and UIs are all over
the map, and brake-pedal switches *have* been known to fail or
go flakey in the past. Newer brake-switches aren't just a single
switch to light the brake lights anymore, either -- they often
have a second set of contacts that goes to control inputs at
ECUs which would more likely be the CC-cancel command. Just
seeing if the brake lights work doesn't prove full functionality.
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With a threshold as low as 20 MPH, is it reasonable to think
that some people wheeling a bit enthusiastically into a parking
lot entrance could still be within their valid "resume" range??
I've seen some pretty stupid/inconsiderate parking lot behavior,
so I'd readily believe it.
.
_H*

My car has an aftermarket rpm-based cruise control. If I set a speed in 3rd gear, then shift to 5th and hit "resume", it WILL try to accelerate to 100+ mph. :p

Of course, I know this, so I can deal with it. Hit the brake, click the cruise cancel, shift to N, etc.