The Mystery of Sudden Acceleration

by on March 12, 2010 at 7:01 am in Data Source, Law | Permalink

Here is Ted Frank on the Toyota sudden acceleration problem. 

The Los Angeles Times recently did a story detailing all of the NHTSA reports of Toyota “sudden acceleration” fatalities, and, though the Times did not mention it, the ages of the drivers involved were striking.

In the 24 cases where driver age was reported or readily inferred, the drivers included those of the ages 60, 61, 63, 66, 68, 71, 72, 72, 77, 79, 83, 85, 89–and I’m leaving out the son whose age wasn’t identified, but whose 94-year-old father died as a passenger.

These “electronic defects” apparently discriminate against the elderly, just as the sudden acceleration of Audis and GM autos did before them.

Statistical Addendum: A number of commentators are worried about selection effects (hat tip Don).  Here is background information from FARS.  In 2008 there were 50,186 drivers involved in a car accident with a
fatality. Of these 8066 were 60 years of age or over. Thus in 2008 the
probability that a driver in a car accident with a fatality was 60
years of age or over was 16%. Using the figures above the probability
that a driver in a car accident involving sudden acceleration in a Toyota was about
54%. Of course, the sample size is very small.

1 Don Lloyd March 12, 2010 at 7:41 am

It seems to me that a potentially serious data selection error is being committed here. With no non-fatal incidents being included here, there will be a bias towards reports of more frail drivers and those who are less capable of a difficult recovery. That’s not to say that the major problem isn’t driver error, but that this report may be weak evidence for it.

Regards, Don

2 Andrew March 12, 2010 at 8:09 am

It is the sudden deceleration I’m worried about.

3 Noumenon March 12, 2010 at 8:14 am

Just like the flu, it could happen to everybody but only kill the old. Not persuaded.

4 CH March 12, 2010 at 8:46 am

Maybe Toyota should add the fogie-feature. Can’t press the engine start button on the dash three times quickly? The car becomes incapable of quick acceleration.

Thinking about my grandmother struggling to double click a mouse button fast enough to open a file, this just might work.

5 nate March 12, 2010 at 9:11 am

Don, with the very first comment, you hit the nail on the head.

6 CH March 12, 2010 at 9:32 am

You could as accurately say, “the drivers included those of the ages 18, 21, 22*, 32, 34, 44, 45, 47, 56, 57, 58” — must be something that focuses on young and middle-aged drivers.

No, you couldn’t.

7 burger flipper March 12, 2010 at 9:49 am

Kevin Miller, look at the byline

8 DanC March 12, 2010 at 10:07 am

It could be that sudden acceleration is more deadly for senior citizens. Perhaps they lack they ability to respond to an emergency situation and the event quickly accelerates to a deadly end. Or perhaps elderly are more likely to die in a car crash generally.

Historically, older buyers tend to buy more GM, Ford and Chrysler cars. If age alone is the root cause, do you see the same pattern across other brands?

Plus I’m not sure that 14 out of 24 (58%) being over age 59 is enough of a smoking gun. Do older people have more accidents in Toyota’s because of a design error that requires quick reflexes to compensate.

Or do drivers regardless of age, but who lack the ability to respond quickly because of other factors (such as fatigue, night driving, medication, distracted , etc), have more fatal accidents.

Perhaps what makes these accidents fatal is the unfortunate combination of a defect in the car and an inability on the part of some drivers to respond quickly enough.

I drive a Toyota. I’m not afraid of it. But I do wonder what is going on.

9 outlawyr March 12, 2010 at 10:20 am

“Juanita Grossman, 77, [deceased] was found with both feet still jammed down on the brake pedal.”

10 Ted Frank March 12, 2010 at 10:38 am

While the average Prius owner is in his mid-to-late 40s, and thus older than the average car owner, younger drivers drive many more miles a year. We’re still talking about a wildly disproportionate number of elderly drivers being affected.

Not all of these fatality cases involved dead drivers; they often involved dead pedestrians, dead passengers, or dead occupants of other vehicles. So the frailty factor may bias age upwards slightly, but it wouldn’t account for anywhere near the entirety of the ratio.

At this point, it’s impossible to compare Toyota sudden acceleration incidents to sudden acceleration in other vehicles: the initial publicity has resulted in a lot of people deciding in hindsight that they were sudden acceleration victims years after the fact, and making late reports to NHTSA. The same thing happened to Audi, which got buried in specious claims after the initial 60 Minutes story.

11 John B. Chilton March 12, 2010 at 11:01 am

@Simon at Mar 12, 2010 10:15:27 AM

We should all read that NYT commentary. Among the points: the elderly do have higher likelihood of stomping on the wrong pedal, and previous well known cases (Audi) predated electronic accelerator systems.

12 dearieme March 12, 2010 at 11:28 am

It’s obviously the car’s engine management system interacting with the driver’s pacemaker.

13 Sebastian H March 12, 2010 at 12:45 pm

“With no non-fatal incidents being included here, there will be a bias towards reports of more frail drivers and those who are less capable of a difficult recovery.”

In addition to Alex’s statistical addendum, the logic of car crashes argue against that. If we were talking about fatality rates in grocery store parking lot accidents at 5-20 mph, the criticism would have more force. But we are talking about cases of runaway acceleration–where the car gets to 70 mph or more and ends in a sudden stop. General physical health isn’t much help in those cases (though being lucky enough to be ejected into a lake might help).

[Most people who survive high speed impacts do so because the thing they ran into was also traveling at high speeds in the same or similar direction, causing a ‘crash’ but not an immediate stop. You don’t have to be traveling even 50 mph for sudden stop crashes (like into a tree or a pole or a wall at 90 degrees) for it to be fatal]

14 A.S. March 12, 2010 at 12:53 pm

* would NOT make any conclusions based on this data.

Apologies for the typo.

15 Gary March 12, 2010 at 1:16 pm

I saw an unintended acceleration accident once. A driver emerged from an underground grocery store parking lot and hit a bicyclist riding on the sidewalk. Instead of stopping after first impact, the car surged forward, plowing the bicyclist across traffic to the other side of the street. The car only stopped because it hit a potted, store-front tree.

I don’t remember the make the the vehicle, but the confused man who stepped out of his car was indeed very old.

Old driver, young victim. Would be nice to get better stats than what we have here.

16 Cyrus March 12, 2010 at 3:04 pm

For selection, the troublesome phrase is “where driver age was reported or readily inferred.” The accident reporter is more likely to include driver age in the report if they believe it is possibly relevant.

Similarly, if the driver was intoxicated, an accident report will almost certainly include that fact. If the driver was not intoxicated, only a fraction of accident reports will inlude that fact. And it would be a mistake to try to deduce the prevalence of intoxication in fatal accidents by looking at only those reports that made a statement of intoxication one way or another.

17 Al Brown March 12, 2010 at 8:16 pm

its also worth noting that older drivers drive less than younger drivers. so accidents involving older drivers are even more significant.

18 DanC March 12, 2010 at 8:58 pm

On a per mile basis, according to the GAO, the elderly are the group most likely to die in a car accident. However they don’t drive much so they don’t have a lot of fatal accidents as a group.

The elderly are more fragile then younger people and will die in an accident that a younger person can survive.

Electronics can adjust the fuel flow but there is no evidence that this has happened in the Toyota cases. Just that it can happen under some extreme case.

Reading the statements in the link you find that about three or four of the accidents are really strange. Most of the others just seem like everyday accidents.

Given the thousands of Toyotas on the road it doesn’t strike me as odd that they would have a handful of fatal accidents that are difficult to explain.

While I’m not sure that Alex has made his case about elderly drivers, there does seem to be more evidence of a pattern pointing in that direction then at Toyota.

19 Bob D March 12, 2010 at 10:11 pm

It must be the test cars that the death panel will be mandating that the old folks will be forced to drive. They have a few kinks to worked out so they don’t take out any productive members of society on their final ride.

20 mulp March 13, 2010 at 3:15 am

To determine if the age bias exonerates the Toyotas, the same bias must be present in all other makes of vehicles.

As I understand accident proneness, the youngest drivers are much more likely to have accidents, then the very old, then the young, with the older but not elder being safest.

So, 50-60 should be among the safest.

Now the bias might be that younger drivers who have Toyota problems are assumed to be reckless drivers and their claims about failures are ignored and never enter the database. If a 17 year old was stopped after driving at 80 down the freeway, would you believe hi if he said the throttle was stuck open?

The only way to begin to eliminate that perception bias of drivers is to compare across all makes and models, but even then, age bias in selecting cars needs to be taken into account.

However as a test engineer with decades of experience with complex systems, there are certainly software/firmware bugs and system design errors.

One design error would be to fail to make sure the car slowed significantly if the brake is applied for an extended time or frequently. (And yeah, I hate drivers who ride the breaks and I think they should be brought to a stop, or at least a crawl so they are taken off the road for obstructing traffic.) If as claimed, drivers were hitting the brakes, then the engine throttle/transmission/engine should shutdown in a progressive fashion. I think this is the type of fail safe mandate that is being proposed.

21 Michael Campbell March 14, 2010 at 10:56 am

> The driver featured in NBC’s 11-minute (!) story on the congressional hearings said she shifted into neutral, but that made the engine rev up, so she put it back in gear.

She also said she used the hand-brake, which is not only mechanical (and thus not part of the electronics) but also controls/brakes the REAR wheels, which are also completely out of the electronic systems. And there was not one shred of evidence this ever happened; no feathering, treadloss, nor flatspotting of the tires.

Was she lying? I can’t say, but what she thinks happened seems to not agree with the evidence.

22 Nathan March 16, 2010 at 10:45 am

I would love to buy a new Toyota if I could afford one. Everyone I know that has owned one loves it and drives it into the ground (no pun intended). Most Toyota owners know that if there is a problem Toyota will find it quickly and address it. Has consumer confidence in the brand diminished at all? I am with Frank on this I’m not the least bit afraid of the Prius. The engine in my Izuzu randomly revs for no apparent reason, so what do you do? The more technology we build into cars the more kinks there will be.

It would be interesting to see how many accelerator malfunctions were reported in the US and globally after the media storm. How tempting would it be to blame the accelerator if you just drove into the back of some poor GM owner? What a convenient problem to have.

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26 FYI June 12, 2010 at 8:42 am

No easy answer for the Toyota problem
By Jeremy Anwyl Tuesday, March 16, 2010
The writer is chief executive of, which recently announced a competition with a
cash prize for anyone who can demonstrate in a verifiable manner the reason for unintended acceleration.
[Included chart in W. Post hardcopy issue: (Toyota and the accelerating mystery; page A19)]
Discrepancy in complaints
Consumer reports of cases of unintended acceleration by manufacturer
(Model years 2005 – Sept. 30, 2009)
Sales (in millions) Complaints per 100,000 vehicles sold
GM ……… 16.5 ………. 0.81
Toyota …. 11.0 ………. 4.81
Ford …….. 10.8 ………. 3.12
Chrysler …. 9.1 ……….. 1.72
Honda …… 7.1 ……….. 1.26
Nissan …… 4.6 ……….. 1.07
SOURCE: analysis of National Highway Traffic Safety Administration complaints
Ghost in the Machine?
Canadian Auto Press
Toyota’s Troubles in 2009: Sign of a Widespread Industry
by Isaac Adams-Hands | 31 December 2009
(excerpt): From 1999-2001 the Lexus ES 350 and Toyota Camry averaged 26 complaints of sudden acceleration each year. From 2002-2004 they averaged 132 each year. Why such a sudden increase? 2002 was the first year that Toyota introduced their “drive-by-wire† systems. It is also interesting to note that when the drive-by-wire system was employed in the Toyota Tacoma in 2005, this model’s sudden acceleration complaints increased twenty-fold.
————————————————————————————Haven’t found that software glitch, Toyota? Keep trying,0,2595172.story

An electronics problem isn’t to blame for the sudden acceleration, say the carmaker’s engineers. That’s nearly impossible to conclusively determine through laboratory tests.

Because of Pathfinder’s high reliability requirements and the probability of unpredictable hardware errors due to the increased radiation effects in space, we adopted a highly “defensive” programming style. This included performing extensive error checks in the software to detect the possible side effects of radiation-induced hardware glitches and certain software bugs.

David M. Cummings, executive vice president of the Santa Barbara-based Kelly Technology Group, spent nine years as a consultant for the Jet Propulsion Laboratory, where he worked on the Mars Pathfinder spacecraft.
Toyota “sticking pedals” recall a smokescreen?
(Version 3, 28th February 2010) 16 pages,%20V3,%2028%20Feb%202010.pdf

The professional opinions of EurIng Keith Armstrong C.Eng FIET SMIEEE, ACGI

Most of their sudden unintended acceleration problems are almost certainly caused by their vehicles’ electronics – either by electromagnetic interference (EMI), and/or lead-free soldering, and/or software “bugs†

1 NHTSA contacted me for advice on EMI and Toyota electronics

The US Government’s National Highway Traffic Safety Agency (NHTSA) has wanted to speak to me for some weeks to discuss the EMI implications of Toyota’s spate of sudden unintended acceleration incidents. They said they wanted to speak to me because they had no one on their staff with my experience or knowledge of EMI and EMC.

I imagine the fact that I’ve been presenting IEEE EMC Symposium papers on EMC and Functional Safety since 2001, including one addressed to the auto industry at a symposium in Detroit in 2008, played a part in their decision.

They also said they wanted to speak to my colleague, Dr Antony Anderson (, a forensic electrical engineer, because they had no one with his knowledge or experience either.
Consumer Reports makes the case for brake override for all
by Chris Shunk (RSS feed) on Mar 25th 2010 (5:56 min video)

We’ve seen demonstrations that show how to stop a vehicle experiencing unintended acceleration before, but this newest video from Consumer Reports demonstrates just how crucial a brake override function can be in stopping a throttle gone wild. CR engineer Jake Fisher lines up a pre-recall 2010 Toyota Avalon and a post-repair Camry to compare and contrast the amount of time it takes to bring a vehicle at full throttle to a stop. Hint: There’s a big difference.

The Avalon went first, and at 60 mph with the throttle open, it took over 500 feet to come to a complete stop – nearly four times the distance of a normally operating vehicle. Even worse, when the brakes were pumped, the ability to stop the Avalon diminished greatly. Pump the brake two or three times and CR shows that you might as well be driving downhill on a sheet of ice.

Next comes the Camry, which has been retrofitted with a brake override system courtesy of Toyota’s recall. The Camry stops at wide open throttle as though the gas pedal is totally disconnected. The result of CR’s little video shows that vehicles equipped with brake override can quickly come to a stop even when the throttle is pegged, making unintended acceleration a non-issue. Hit the jump to watch the six-minute video for yourself and let us know if you think all automakers should adapt this technology in the post-jump comments.
[Source : Consumer Reports]

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