Unintended Acceleration

by Volker Weber

Toyota is currently learning something Audi has learned a long time ago. The phenomenon "unintended acceleration" is a technical problem that only manifests itself within the jurisdiction of the United States. The solution is simple and has been implemented by several car makers. In a vehicle where both pedals are pressed, the brake pedal overrules the other one. A third pedal does not complicate things as it only helps to avoid the problem.


Every time I read something about this issue I'm asking myself why it's not possible for the drivers of this accelerating cars just to switch from "D" to "N" and press the break. I tried this some days ago in a BMW with automatic gearbox - no problem, even during fast acceleration.

Sven Semel, 2010-03-15

Is the problem sitting at the steering wheel?

Jan-Piet Mens, 2010-03-15

My uncle told me(he works for a big automotive supplier), that Toyota had this feature implemented but they had problem with it, because a lot of people in the US drive with the left feet on the brake and the right feet on the gas.
That leaded to accidentaly pressing of both which started a emergency brake.

That is why they removed it. Now they implement it again.

Patrick Bohr, 2010-03-15

It's a scam by the US to get back at Japan for buying their dept from China.

Look at the recent incident:

Listen to the audio - 2 minutes in (at 90 miles/hour), and the 911 operator asks for name and phone number before giving advice? Ridiculous.

Frank Köhntopp, 2010-03-15

"In a vehicle where both pedals are pressed, the brake pedal overrules the other one."

Why would one want to do that? If the car accidentally accelerates (which I think is the problem) I step on the brake - or not?

Joachim Bode, 2010-03-15

That's how it works outside the US. Apparently not inside.

Volker Weber, 2010-03-15

@Joachim: Try driving with your left foot on the brake, right foot on the accelerator. Then confuse your feet :-)

Ole Saalmann, 2010-03-15

Maybe part of the "problem" is the amount of money you can sue out of a large company in the US compared to what you can get in Europe.

Hynek Kobelka, 2010-03-15

@Ole: I would have to retrain my muscle memory first.

Joachim Bode, 2010-03-15

It took a long time and a large number of reported issues before people over here stopped laughing at the supposed morons reporting the issue. It's cute to poke fun at the dumb Americans, but how about a little logic?

It's well known that Americans, in far larger numbers, spend far more time driving than Europeans (in fact, this is a common complaint made by people who want the US to do more to stop global warming). Maybe the problem is statistically unlikely in a population that doesn't create enough data. Maybe the problem only shows up when you put a certain load upon the car. Most of us are IT geeks - we all ought to be familiar with problems that are difficult to reproduce in some scenarios, but show up with regularity if you isolate the problem. Maybe there have been a few Europeans who've seen the issue, but not enough of them for them to have heard of each other and gotten together to push it?

The joker on the CA freeway doing 90 aside (he's a scam artist), the reports have come from all kinds of people long before anyone would listen to them. Take shots at the moronic Americans if that's how you entertain yourselves, but don't for a second believe there isn't a real issue here.

Rob McDonagh, 2010-03-15

@Patrick "a lot of people" I don't believe so. Not at all. In my life I have known one person who drove with both feet (one on accelerator one on brake), my grandfather. I have never met another person who was trained to drive with both feet (except for manual transmission of course, but then just for the clutch). Apparently it was popular in the 1930s as early autos had the pedals so far apart, and for some his age - 92 and no longer driving - it was the way they learned.

Rob Novak, 2010-03-15

Wow. I'm an American who loves my manual transmissions, but seriously guys - to blame this as a "moronic American" problem is ludicrous.

Rob is absolutely right that we Americans drive more than any other country. Plus, if I had to guess, there's more Toyotas sold here than anywhere else in the world. And less than 10% of cars in America are manuals. Versus what percentage in other parts of the world?

People with manual transmissions probably would never make press with this. You'd push in the clutch, pull over and stop. I'd get it repaired or examined, or in some way it would be resolved and likely never hit the press.

This doesn't need to be a percentage game, just a couple of these incidents is enough to warrant concern and statistically speaking you just don't have enough possibles in other countries to make it occur.

@Sven - The modern E9x series and E6x series BMWs (3 series and 5 series, respectively) have electronically controlled automatic gearboxes. When you push the lever up you are *requesting* neutral. You may not get it. I haven't checked but this is quite possibly a similar situation with affected Toyotas -- your real transmission behavior is at the whim of a computer.

Erik Brooks, 2010-03-15

I don't think Americans are less clever than Europeans.
That the problem came up in America at first is just because there most of the people drive with an automatic gear while in Europe most of the people still drive with a manual shift. Don't really see the reason for a manual shift but it most cases its a price question.
That people drive with two feet in an automatic car is a habit which is just not as the developer wanted it to be. My driving teacher would have killed me for that.
Another problem in that case is surely that you can't really pull the park brake handle or turn the key to switch the car off. Some dumb electronic or mechanical system would be nice sometimes.

Patrick Bohr, 2010-03-15

Yeah, this is like the Audi issue - once the media picks up on it, suddenly tons of people start having the "problem". I'm not saying there isn't an issue, but I find it curious that the number accelerate so much once there's media coverage. We may not be stupider, but we are media whores.

Amy Geek, 2010-03-15

I frequently (at least once or twice a week) see cars driving with the breaklights on while accelerating or going constant speed.
So there is a certain number of drivers who for some reason drive like that. I live in Texas, and most of those vehicles observed driving like that are pickup trucks.

That is by the way the same category of vehicles that always accelerate really slow at the traffic lights or freeway onramps ("I am so heavy, it takes time to get up to speed") but later drive down the freeways 20-30 mph faster than the speed limit ("Oh, I had no clue that a heavy vehicle is harder to stop than the small car in front of me that just were breaking...").

The only pickups you see going the speed limits are driven by hispanics. Obviously they are attempting not to draw the attention to themselves by the police, perhaps having something to do with their immigration status.

Karl-Henry Martinsson, 2010-03-15

Rob, Rob and Eric. I am not insinuating you are stupid. But I do think that people who cannot stop their car are. The brake of a car has more power than the engine(s). You can stop a good car in less than 40 meters from 100 km/h to a full stop. But you can never accelerate a car from a stop to 100 km/h in 40 meters. No matter what the engine does, you can always stop the car by stepping on the brake. And that is an hydraulic device.

You can however wear the brakes down. Simply by leaving your left foot on the brake pedal. This will heat up the brake and thus the brake fluid, until it no longer works. That's an operator error.

Toyota's design fault is simple. They let the accelerator pedal work independently from the brake pedal. You can brake and accelerate at the same time. Other carmakers have long coupled them. If you leave your foot on the brake, your car will not accelerate. That is a simple and effective bozo filter.

Volker Weber, 2010-03-15


I had a E61 and E70 with electronic/automatic gear box and both could be switched from "D" to "N" under every driving situation. I tested this because after 20 years in IT business I'm always a little scared commit my live to a piece of software written by someone I doesn't know. Sometimes driving with the right hand on the lever I switched accidentally to "N" in case of a little stronger usage of the brakes.

It's possible that the US Version of the cars have different settings in the software which prevent one to switch from "D" to "N" but I could not see any reason for that.

Sven Semel, 2010-03-15

Sven, the Prius is basically fly-by-wire. A computer coordinates an electric motor and a combustion engine, which drive the same gearbox. The gear "lever" is a joystick. When all systems work well, you can of course go from D to N. The alleged system error is that (a) the car accelerates, and (b) at the same time ignores the joystick. I don't find this credible, but it is not generally impossible.

Now, at the same time the brake also needs to fail. And the engine off switch must also be not operational. That is a little hard to stomach. Occam's razor applies.

Volker Weber, 2010-03-15

We all agree, though, that the car randomly (and exceedingly rarely) accelerates when the driver doesn't want it to, right? I don't consider hitting the brakes to be a solution to that problem, though I think our ITIL board would agree that it's an acceptable workaround. heh...

The initial reports were from drivers who hit other cars from behind, where they simply didn't have time to hit the brakes because they were in low-speed, city traffic zones with little space between cars. I find those reports believable. The insurance companies did not, and Toyota paid off US govt officials to ignore the issue as well.

Rob McDonagh, 2010-03-15

Rob, actually I don't agree on that. It is rather unlikely that the car decides it needs to accelerate without input from the driver. There is a known problem with some accelerator pedals in Toyotas. I once had a VW Beetle that had the same problem. You would step off the accelerator but the pedal would not return to idle. You actually had to either bend down to fetch it with your hand, or with your foot, which I quickly learned to do. I have also occasionally dropped something on the floor which could have gotten dangerous pretty quickly.

Toyota is fixing this accelerator pedal problem with pairing a plastic surface with a metal one, where there currently are two plastic surfaces. It's a mechanical upgrade to make sure the dampening of the pedal does not interfere with the force that is supposed to bring the pedal back.

The Woz has claimed he can provoke a situation where his Prius acts up. To my knowledge he has however not come forward with an explanation. Since the Woz is certainly not an imbecil, I would really like to get to the bottom of his story.

Volker Weber, 2010-03-15

Perhaps it is like MS Windows where one has to click Start to Stop?

Dennis Ellison, 2010-03-15

Volker, I totally agree. It's very unlikely that all errors happen at the same time cause there is no main computer coordinating all the functions but different control units for the gear box, the engine etc. The single control units (at least for the main functions) have a emergency mode switching back to basic functions in case of malfunction or loss of contact to the bus system.

I've seen that on my wives Mini. The Control unit for the light and some other minor functions was broken. The result was that the car switched on the dipped head light everytime for security reasons. I can't believe that Toyota (or whoever build the control units) did not implement such security modes. So I guess that the accelerator pedals have a problem and the drivers were completely overstrained. It's unbelievable that some of the drivers were able to call 911 and explain the problem but not to think some seconds about basic functions of the car and try something to stop it.

Sven Semel, 2010-03-15

Good lesson in irony. British irony, not what Americans call irony:

British engineer, discussing laser etching of mirrors: "We don't print 'Objects in the rear view mirror are closer than they appear' on our mirrors."

American engineer, curious: "What do you print on your mirrors?"

British engineer, without batting an eye: "Objects in the mirror are behind you."

True story.

Volker Weber, 2010-03-15

Awww, I was gonna make an American irony joke. Damn. Too late.

Volker, we certainly agree that the Woz is not an imbecile. His issue is supposed to be cruise control related, and he claims it's a software bug. He's got a fair amount of credibility with me, but even he's not automatically right.

One of the people who crashed because they couldn't stop accelerating was an off-duty state trooper. He and three members of his family died in the crash. Of all the people who shouldn't panic when a car starts acting up, I'd put a state trooper behind a professional driver and a stunt man, but that's about it. I find it hard to believe that particular incident was 'death by stupidity.'

I'm not sure why you said that we don't agree about the acceleration. I said that the car accelerates when the driver didn't want it to. You pointed out the hardware fix Toyota built to correct a problem where the acceleration pedal wouldn't come back up. Doesn't a stuck acceleration pedal cause increasing acceleration until the point of equilibrium is reached? If the driver hit the accelerator hard (floored it), their speed wouldn't level off for quite a while. Of course, the brake workaround still holds true. Or should, anyway.

Rob McDonagh, 2010-03-15

@Rob Novak: I can't really prove it to you, but I believe in my uncle. Karl-Henry was stating the same from his own experience.

I know that an Audi A6 starts an emergency braking sequence if you pull the park brake switch for some seconds. Something you probably wouldn't know if you didn't read the manual.
Stopping a car if it accelerate unexpected is pretty tough. If there is nothing like a clutch to press without thinking, most of the people probably ends up in an accident. Braking with full accelerate sounds hard to steer.

In the end I'm just happy that it didn't happen to me.

Patrick Bohr, 2010-03-16

I find it hard to believe that particular incident was 'death by stupidity.'

I agree it is hard to believe, but every profession has stupid people. It terrifies me to no end that this includes doctors.

I do not know what state troopers learn about driving. I would not necessarily put them on the same level as people who practice driving on the edge like professional test drivers. Nobody has their expertise.

What I do know is that most, if not all of the non-professional drivers have no idea what their brake is able to do. Because they never use it to its potential. Mercedes has pioneered a system that monitors the driver and identifies when he attempts a panic brake and then it applies the full force the driver never applies to the system.

It's pretty easy to copy. Buckle up. Find a straight road. Bring the car up to 40 mph*. When nobody is behind you, step on the brake with your LEFT foot with full force and do not release until you have come to a full stop. This should be less than two seconds. If you had not buckled up, you would have hit the steering wheel, if not the windshield. We are using your left foot since it has never learned to hit the brake pedal softly. Full force means, try to break the pedal. It won't. :-)

The aforementioned panic stop initiated by the electronic parking brake is exactly the same experience. It's pretty earth shattering.

Doesn't a stuck acceleration pedal cause increasing acceleration

Yes. It continues to apply the user input. What it would not cause is a sudden acceleration without user input. That is what is missing from the Toyota. Putting your foot on the brake should cancel this input immediately. Like it does switching off the cruise control.

Stuck pedal or not. There are a dozen ways to stop a car with a run-away accelerator. Hit the brakes full (!) force, switch off ignition, put transmission into neutral, apply parking brake. Those are the non-destructive ones that come to mind. Driving the car into a guard rail at a small angle is the most effective one if you no langer have a working brake. Expensive, but life saving. Obviously you cannot test this. ;-)

*) 40 mph is just so that you do not panic. This works at all speeds.

Volker Weber, 2010-03-16

@Sven - It's still software. In the US you can do this:

1. Get in a new automatic E6x series, open the driver's side door. Don't buckle your seatbelt.

2. Start the car, leaving the door open. Put car in reverse. Take your foot off the brake and let the car begin rolling backwards.

3. Once the car hits about 5 mph it will switch to PARK (abruptly stopping the car) and alarm about the door being open.

So I could see it being absolutely possible (though it should be highly unlikely) that requesting Neutral results in you still being stuck in drive.

Also, brakes do fade under heat and constant braking, eventually becoming ineffective. It's definitely possible in the runaway scenarios that the driver's repeated attempts to slow the car killed the ability for them to work at all. But you're right - if they had hit the brakes full-force before the brakes were smoked it should have stopped the car. Though I don't know if this includes Prius' -- their regenerative braking does rely on load from the generator which wouldn't be there if the accelerator was stuck. I don't know how just the brake pads would fare in that case.

Emergency/parking brakes are fairly useless. Most people don't have them tightened up, and they typically only engage ONE of the rear wheels. Even if both are engaged (as is the case on many fine German automobiles) it's usually the rear wheels and many cars are front-wheel-drive. It's better than nothing though.

@Vowe - Many roads in the US don't have a guardrail, though driving offroad might very well slow you down enough in many cases to come to a stop.

BMW's brake system does something similar to Mercedes'. If you press the brake at a high speed but not quite at full force it assumes you want to panic stop and applies full force for you.

As a less drastic measure it will also sense the speed at which your foot leaves the accelerator and (if that speed is high) pre-pumps the braking system so the pads are already in slight contact with the rotors in an attempt to anticipate your upcoming rapid braking.

I agree 100% about the importance of knowing your vehicle's brakes. Hitting them hard in a controlled environment is in my opinion the #1 thing all new drivers should do as they are learning to drive.

Erik Brooks, 2010-03-16

@Volker: I don't think it's very non-destructive for the engine to put transmission into neutral while the engine's running with full throttle, but of course it's absolutely life-saving.

The other point is that emergency-switching off the engine of a Prius, as I've seen on a video, is just like turning off a computer: you'll have to push and hold the ignition-button for 3 seconds. And 3 seconds waiting at a mentioned speed of 100 mph means about 134 m to go hoping you have nothing in your way...

Besides that I fully agree that there's always a save way to stop your car, even if it's unintended accelerated.

Markus Jabs, 2010-03-16

@Patrick -

A reason I can give for Europeans preferring manual over automatic is that the driving conditions are different. We have loads of narrow, winding roads, and our cities are far closer to another. The perception (which I share) is that one has more control over the car when driving manually.

Andrew Magerman, 2010-03-16

I had a emergency brake training last year. It was my very best investment into live insurance ever. Very much insight - be it for a beginner or seasoned driver.
Besides that it is lots of fun.

Fact is that in gemany alone the number of deadly car accidents was cut in half during the last decade, which I contribute largely to ASB, ESP and co. On a general basis those systems work as intended. It remains to be investigated what is really going on in the Toyota.

Boeing had a similar problem, under some very rare circumstances the rudder reversed itself. This is counter productive on final approach in bad weather. It took a long investigation to find that out. Of course such a failure is technically "impossible", so all crashes were attributed to pilot error in the first place.

Jörg Hermann, 2010-03-16

That makes me very wary of cars without a physical key and switch. I agree that 3 seconds for an emergency switchoff seems long...

Lars Berntrop-Bos, 2010-03-16


most (if not all) usual cars have today a engine speed limiter. So you can't blow up the engine switching from "D" to "N".

Jep I know, same with the E70. Very funny if you try to maneuver a trailer in a small doorway around a corner.

Sven Semel, 2010-03-16

-Stuck pedal or not. There are a dozen ways to stop a car with a run-away accelerator. Hit the brakes full (!) force, switch off ignition, put transmission into neutral, apply parking brake

Prius have no key you cant turn off the engine while the car is moving to avoid steering lock , you cant put it in neutral , if you hit slam the breaks while doing 60+ the breaks will burn out due to engine pressure still being applied (at least thats the version i heard from a toyota tech)

But time will tell , there been a incident in norway a few days back so hopefully it will help finding the error

Flemming Riis, 2010-03-16

Hm, I knew a truck driver who was driving a Mercedes Benz truck. At some point, the relays which controled the brakes, got jammed and it was not possible for him to brake at all - no brake worked until he was speeding through a village, over a red light and out of the village when the relys released and the braked were working again. Lucky for him, it was very early in the morning and no one was on the street at that time.

This incident was of course "Technically impossible" and "A driver issue" until it happend to more trucks from the same company. Still, this was about 20 years ago...

Jan Fuellemann, 2010-03-16

@Jan Fuellemann:

My last (and only) experience with trucks (real trucks) was in the Dutch army: the brake system was fail-safe; if the brake system got hit / out-of-order, you could only break once, and then NOT releases the breaks anymore. Reason: you needed a full functioning brake system under hydraulic pressure to *release* the brakes.

Also about 20 years ago. So I would expect that same fail-safe system on commercial trucks too.

Eva Quirinius, 2010-03-16


Trucks have usually pneumatic brakes which behave like described. But as mentioned above, all that is today controlled by software, so everything can happen as long as it's physically possible.

Sven Semel, 2010-03-16

When people learn to drive, hitting the brake becomes instinctive. When something unusual/ unexpected happens in your car, you have to use your conscious brain instead of the subconscious part - which takes much, much longer. That's why it is dangerous.

I had problems with an accelerator cable sticking once (a hardware rather than software problem). I quickly figured out what to do and all was well, but am thankful that I was on an almost empty road when it happened.

Nick Daisley, 2010-03-18

Hm, there may be some news soon. This is the sort of incident that I'm most interested in: during a period of a couple of seconds, the car accelerates unexpectedly for whatever reason, causing a collision or incident, but the driver is not hurt and does not appear to have any ulterior motive. Highway scenes are more dramatic, but lower speed, urban or tight space scenarios are more likely, because there's a great deal less time to react. During that brief, "What the @#$%^" moment when the driver realizes something's wrong, the car has already passed the point where the brakes are useful. Without more information, nobody can say whether this incident was real or not, of course.

Rob McDonagh, 2010-03-18

First hand testimony. Something is definitely going on. It's not just driver error.

Charles Robinson, 2010-03-18

Another driver error. I don't trust these accounts at all.

Volker Weber, 2010-03-19

From here (emphasis mine):

Another driver, John Moscicki, of Lake Oswego, Oregon, told the AP that his 2007 Toyota Camry suffered unintended acceleration five times prior to having his floor mat modified during the recent recall. Moscicki went on to explain the details of an occurrence on March 4, after his vehicle was treated for the recall in which his Camry accelerated out of control, yet again.

“It just went to the floor like some other system had control of it,” said Moscicki, who, according to the AP, also raced high-performance sports cars and previously owned a Porsche restoration business. Moscicki also explained that when the vehicle began accelerating from a standstill on the freeway – up to 50 mph – Moscicki was able to stop the acceleration by shifting into neutral while simultaneously braking with his left foot and prying the accelerator pedal away from the floor with the top of his right foot.

Rob McDonagh, 2010-03-19

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