YIKES: Experienced unexplained acceleration, already had brakes reprogrammed

I have to admit I don't like the cruise control stalk or any of the stalks rotating with the steering wheel. I'm frequently reaching to the wrong place because the stalks are not always fixed relative to my shoulders. Heck, sometimes the stalks are 180 degrees and inverted from where they would be if running straight.

Another advantage of a fixed stalk location is they can extend out a bit further than the diameter of the wheel. It makes it less likely to have to 'reach around' the steering wheel to operate the control(s). The wiring doesn't have to deal with steering rotation so it becomes simpler and less subject to flex wear.

Bob Wilson

 

Honestly you should not have the cruise control on at all if you're in a situation where you have to slow down enough to go around a curve. I don't mean just cancelled, you should turn it off. If you ever have to take your hands off the steering wheel to find the cruise control, you're doing it wrong.

 

Cruise control and wet or slippery roads don't mix either.

 

What if you have slowed down temporarily for a car in front and then go into a RH curve?

If you want to turn cruise off part way through a bend, you are likely to have to take one hand off the wheel or at least slide it around the wheel to find the wheel mounted control stalk.

 

Much less being used in the rain. Why was it even on if it was raining?

 

I use CC most all the time. But I always Cancel CC with the brake pedal and never use that function on the CC stalk. I almost never use the CC Resume function but prefer to use Set especially when keeping my distance in variable traffic speeds. Maybe disabling the Resume function on the stalk would be at least a temporary (until redesigned) solution should this prove to be a major reason for unscheduled accelerations?

 

I would personally prefer to have the CC stalk in a fixed location but it is where it is and I knew this when I bought the car. I think reporting this to the NHTSA as a safety concern is a little extreme.

If the car manufacturer's need to pay attention and address every complaint to NHTSA, we might as well park the cars and go back to horse and buggy.

 

This is in response to my post asking why the CC was even on in the rain, when it isn't safe to do so?

Anyway, regarding what you wrote, I had the cruise control buttons on the steering wheel in a previous car and it was a lot more convenient. I don't really like the stalk design, as it's hard to get to. But at least the unscheduled acceleration is easily canceled by the user so I don't think it poses much of a safety issue (as the OP likes to claim). An argument that an unscheduled acceleration would be dangerous to occur in a curve in the rain does not hold water (pun intended) because it's the OP's own fault that the CC was on in the rain. The CC is also not meant to use on a curve (especially a tight one where you run the possibility of interfering with the stalk).

 

this CC issue is interesting but i doubt that anyone uses CC more than i do. i pretty much use it 95+% of the time. i have minimal issues operating it and yes a few times i may have accidentally engaged it at set speed higher than my current speed and got much more acceleration than i desired at the time which was alleviated by tapping the brakes, issue resolved, took a fraction of a second which is about twice the length of time that i was concerned about the issue.

as far as the actual design of the CC. i dont really like it either. i rather it be stationary as well like windshield wiper controls. i do understand the concept and if my hands were always at the same position on the wheel (they are most of the time, but i have found it not nearly so convenient since the turning ratio was jacked up) then i could see it.

 

I've got a potential test track to try and replicate the symptom:

What I'll do is:

• warm-up car
• set cruise control to 70 mph (local highway speed)
• 'cancel' so it is ready to 'resume'
• drive to test track (above)
• enable accelerometer
• measure right hand turns at 25 mph (posted speed limit)
• measure straight-line, CC 'resume' acceleration on flat
• measure right hand turn and CC 'resume' acceleration

I've got the accelerometer near my right hand and should have time this afternoon to run the test. But as I tried to point out earlier, I have no problem with parallel reporting something happening to Toyota, NHTSA, PriusChat or any other problem solving place. Let's not become known as a place that is hostile to user reports but treat them as 'a new puzzle.'

The good thing about shared, reporting here is we have 'skin in the game' and depending upon time and resources, will check it out. We also are pretty good at pattern matching so three months, six months, or a year from now when someone else 'rediscovers' what we think is going on, we'll have a handy and accurate description.

Bob Wilson

ps. I am well aware of the topology of this test track:

It is a reasonable place for getting metrics.

 

The problem is that CC can be used any time but the manual on page 217 gives logical cautions on when not to use it including when roads are wet and turning it off when not being used so it won't be accidentally Resumed.

Is that enough? Maybe the CC icon and its 'Set' icon should be relocated next to the speedometer and both be in amber instead of green? Move the green drive modes to the HSI screen.

So the CC is a real plausible cause for unscheduled accelerations. Are we willing to accept that as the only way this original OP acceleration occurred? Are there any other ways a 'normal' unexpected acceleration can occur besides the CC?

 

I would normally agree except that in this case of unscheduled accelerations Toyota is caught up in rash of them for unknown causes. And part of this may be unfamiliarity with the vehicle systems and how to react properly if there is a sudden unscheduled acceleration.

I've changed how I use the CC just from reading and thinking about this thread. I think the NHTSA and Toyota need all the possible input on unscheduled accelerations they can get.

 

Is Toyota really caught up in a rash of them, or is this like a few summers ago when the media kept reporting shark bites. It seemed that the world's sharks had all gone crazy and become man eaters. After the hysteria died down and the totals were tallied, it turns out that there had been fewer than normal shark attacks. The only difference was that a particularly gruesome attack had caught public attention early in the season, so every additional attack was duly reported in graphic detail.

Tom

 

I've accidently activated the windshield wiper controls quite a few times.

On package V with the ATP, the dynamic radar CC display takes over the entire HSI screen when on (and you can't disable this display), yet a few posters have been taken by surprise when their Prius "unexpectedly accelerated."

Many other possible explanations have been offered earlier in this thread.

A lot of it (could be as much as 85% unaccounted for) could be psychological in nature.

 

BAD NEWS: I forgot that dropping below 23 mph erases the previous 'set' speed (NHW11 model, ZVW30 remembers.)

GOOD NEWS: Many cloverleafs incorporate a banked, curve that can be taken at 25 mph. The problem is banking changes the centrifugal force towards the seat instead of the side.

I'll start scanning the interchanges to see if there is a way I can exit an interstate and encounter a right-hand curve without having to come to a complete stop. Google map, let's see what is available. I would prefer an unbanked or lightly banked, 25 mph speed, right hand curve.

Bob Wilson

 

On mine i can come to a stop and when starting up again i can hit resume at 23/24 mph and it will go to last set speed.

 

Mine too. I can stop at a stop light on the highway on the way to work and start over and hit resume and go back up to set speed.

 

OWCH! I tried it with our NHW11 at lunch time thinking they had the same CC control rules. The NHW11 'forgets' as soon as the speed drops below 23 mph.

Well it is evening so I'll take the wife's ZVW30 over to the test track and give it a go!

Bob Wilson

 

Ok, here are the accelerometer results:


This is the track:


The test curve is the lower left and the straight segment is the bottom from the light gray topped building to the curve. The test drive was clockwise so most turns were right-hand turns. This would be consistent with steering motion that might put the cruise control to 'resume' a previously set highway speed.

Cruise control, resume acceleration in the curve significantly increases the centrifugal force. This may give the illusion of more power than is actually being applied. Note that the "SET" light comes on if the cruise control "resume" activates.

Additional Detailed Charts:



Also:


The increase in centrifugal force, the lateral acceleration, is driven by the increase in velocity. Per Wiki, the Force is given by:

F = (m (v*v) ) / r
​

Radial acceleration in the curve increases the force by the square of the velocity

Bob Wilson