Tag Archives: Safety

ET ALERT: Toyota ‘Unintended Acceleration’ Is Still Occurring


Despite claims that Toyota’s problems with unintended acceleration have been due to driver error, or cured via floor-mat adjustments, a recent case has been reported wherein neither of those factors were relevant. As reported by “Charles” in a message to Engineering Thinking:

The following events occurred on May 15, 2015 while driving from Charleston, SC to Nashville, TN (I-26, I-40) in my 2012 Toyota Highlander.  Normally interstate traffic is so congested it prevents use of cruise control; however, that morning I was able to turn it on and set it on 75 MPH.  As we were coming up on slower moving traffic, I applied the brakes to switch off the cruise control and it did not work – even after pumping the brake pedal.  I then used the off/on on button(switch) on end of cruise control lever to switch off cruise control – and that worked. If that switch had failed – or if I had panicked – then I would have had a “runaway” Toyota.  The car did not accelerate, but when you are standing on the brakes and the car is still “cruising” at 75 MPH it sure feels like it is accelerating.

Later on during the same trip I tried the cruise control again (several times actually) and each time applying the brakes would not switch off the cruise control.  Whatever is wrong with the cruise control system, on this Toyota, it is what we call in my line of work a “solid fault” – not intermittent.  I feel confident that my car will repeat the scenario every time it is tried…

…I am a semi-retired Electrical Engineer with over 40 years in the power industry.  For approximately 5 of those 40+ years I worked as a field engineer, testing and commissioning power control systems.  So I know a little something about how control systems (cruise or otherwise) are supposed to function.  I would like to add, that in my testing/commissioning experience, I only had one programmable relay that failed out-of-the-box, and it was not a software problem.  All the problems I encountered were related to wiring and/or wiring design … I strongly suspect the Toyota “problem” may also be related to wiring (wiring harness, assembly process, etc) not software.

…Please note, our Highlander has the factory floor mats which are held in place by two hooks.  My cruise control issue had (has) nothing to do with floor mats….


Charles’ expert qualifications and detailed report are compelling evidence that Toyota still has a serious issue that cannot be dismissed by blaming the driver or the floor mats. My thanks to Charles for sharing his experience, and for alerting Toyota owners to the fact that ‘unintended acceleration’ is still a very real possibility.

Prior posts on this issue can be found at the following links:

Toyota Unintended Acceleration: “No Electronics-Based Cause”: Not True & Misleading

Customers Claim “Fixed” Toyotas Are Still Accelerating

Toyota’s “Drive By Wire” Throttle System Suspected As Crash Cause

Stop Driving Recalled Toyotas

Toyota Unintended Acceleration Causing Deaths And Injuries

-Ed Walker


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ET EXTRA: Why Medical Care Is So Hazardous

“…as much as 90 percent of the published medical information that doctors rely on is flawed.”
From “Lies, Damned Lies, and Medical Science,” by David H. Freedman, 23 Aug 2011, The Atlantic

ET Corollary: Don’t be afraid to ask your doctor probing questions, to challenge his/her assumptions, and to do your own research.


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Protecting Your Life: The Public Has Been Misled about Airport Body Screening Risks


Good overall summary here: Cancer Surges In Body Scanner Operators; TSA Launches Cover-Up

Original source material here: Electronic Privacy Information Center


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ET EXTRA: Protecting Your Life: Customers Claim “Fixed” Toyotas Are Still Accelerating

Engineering Thinking Extra Is A Short Review Of A Current Hot Topic

“…the Department of Transportation released data Thursday showing that more than 60 people have complained of sudden acceleration incidents in vehicles that have been repaired by Toyota as part of the recalls to address the problem.”
Los Angeles Times, “Top lawmakers want more data from Toyota,” 6 March 2010.

The problem with Toyota is not that they have experienced a problem. All technology products have problems, although for high quality products the problems are usually minor and only affect a small percentage of products sold.

Problems occur because, despite our advances in technology, it is a simple fact that it’s not humanly possible to achieve a perfectly safe and reliable product. Plus, the price tag for trying to achieve perfection always reaches a point where the customer is not willing to pay the price. We all would be safer if we drove vehicles that were built like tanks, but their low fuel efficiency, cumbersome performance, and high price would make them much less attractive, all things considered, than the less-safe autos that we willingly purchase today.

Also, technology is not capable of completely compensating for human error. Drivers can mistakenly step on the gas pedal rather than the brake pedal, and in a panic keep their foot jammed to the gas pedal because they think they are stepping on the brake. (In engineering parlance, this is an example of a feedback loop that has — because of the application of foot to incorrect pedal — changed abruptly from a stable loop to a completely unstable one.) Although I have not seen any convincing data on how often we should expect human error to create “unintended acceleration” events, the hypothesis is plausible and should not be dismissed.

No, the problem with Toyota is not that they claim that human error is sometimes to blame, or that they have some product defects. The problem with Toyota is their response to the issue, which has been documented to be one of delay and obfuscation (link). This demonstration of poor character is what may kill Toyota.

An avenue of investigation that I have not seen addressed by Congress is a request to review Toyota’s design validation documentation. This would be the set of analyses and test reports that are the gold standard for high-reliability products. The analyses would include a Worst Case Analysis and a Fault Tree or a Single Point Failure Analysis. In my view, if these documents do not exist, it indicates that Toyota has not adopted “best engineering practices” regarding safety-critical products.

If they do exist, they can be reviewed for thoroughness and accuracy. And if they are thorough and accurate, there is a high likelihood that the problem has already been identified. If so, this means that Toyota ignored their engineers for cost-containment purposes, to the detriment of public safety. Toyota is acting as though this indeed is what happened.

Toyota: show us your analyses.

-Ed Walker


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ET EXTRA: Protecting Your Life: Toyota Joins The Gallery Of Shame

“Toyota officials claimed they saved the company $100 million by successfully negotiating with the government on a limited recall of floor mats in some Toyota and Lexus vehicles, according to new documents shared with congressional investigators.” …

“The savings are listed under the title, “Wins for Toyota — Safety Group.” The document cites millions of dollars in other savings by delaying safety regulations, avoiding defect investigations and slowing down other industry requirements.”

-AP as reported by MSNBC


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ET EXTRA: Protecting Your Life: Toyota’s “Drive By Wire” Throttle System Suspected As Crash Cause

“Toyota car recall sparks ‘drive by wire’ concerns”

-New Scientist

Over the years some of my colleagues and I have cautioned against placing too much faith in systems that insert an electronic link between the operator and the controls of aircraft. Such systems are called “fly by wire” (the “wire” being the electronic link). Electronic linkages in recent years have started appearing in automobiles, so we now have “drive by wire,” where the wire replaces the old mechanical throttle linkage.

Why are some engineers such as myself so cautious? Because we are the ones who do the detailed design and analysis and testing, and we know the risks. We have predicted and observed the damage caused by glitches in electronic linkages, such as power outages over large parts of the country, patients erroneously exposed to deadly doses of radiation during medical scans, and various other catastrophes.

Sometimes new technology seems cool, but sometimes it’s also half-baked and contains hidden risk. To protect yourself, here’s a saying that may help:

Don’t Be The First One To Stick Your Toe In The Water,
Unless You’ve Got A Toe To Spare

-Ed Walker

As conservative

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ET EXTRA: Unintended Consequences

Engineering Thinking Extra Is A Short Review Of A Current Hot Topic

An essential Engineering Thinking principle is thoroughness. This involves not only checking the details, but also exploring nooks and crannies to be sure that all the details were indeed checked. The best engineers will do this, plus will stand back and look at the big picture to try to spot unintended consequences; particularly when dealing with critical safety issues.

There is nothing more disheartening than thinking you’ve done a great job, only to find out later that you missed a subtle but important flaw, and you’ve made things worse instead of better. Despite our best efforts, this does on occasion happen to all of us, sooner or later.

A recent example of unintended consequences is the switch to efficient LED lighting to replace older incandescent bulbs used in traffic lights. Municipalities have found out to their chagrin during the recent snowy weather that LED lights do not emit enough heat to melt off any snow that may cover them up, resulting in traffic hazards and expensive manual maintenance to keep the lights uncovered. By contrast, the older inefficient incandescent lights gave off enough heat to melt any snow, so “snowy weather maintenance” was not required.

(Ref. “LED Traffic Lights Don’t Melt Snow,” by Mark Frauenfelder)

-Ed Walker


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