NHTSA Tracking Braking Loss on Prius Hybrids

Toyota owners are unhappy about the performance of the system, calling it defective. Pedestrian lives at risk?

by on Dec.24, 2009

Drivers are unhappy about stopping distances on bumps, tracks and slippery surfaces.

Dozens of owners of the current third generation Toyota Prius models have filled complaints with the National Highway Traffic Safety Administration about the alleged brake failures they have experienced.

The Office of Defects Investigation has at least 33 complaints that we are aware of from Prius owners alleging a problem or safety defect, often about the design or performance of the braking system, which recharges the battery when the Prius decelerates.

Some owners describe this as unintended acceleration, but a review of the complaints by TheDetroitBureau.com leads me to think that this is an issue about how the braking system is calibrated. Whether this is a safety related defect is ultimately up to NHTSA to decide. The safety agency is authorized to order manufacturers to recall and repair vehicles when ODI investigations indicate that they contain serious safety defects in their design, construction, or performance.

For Toyota, it is another owner satisfaction or quality issue, at a minimum, coming from its most advanced technology vehicle at a time when Toyota is under attack for its handling of safety matters.

Braking performance issues?

In the case of the Prius brakes, it appears that the transition from regenerative braking to hydraulic braking is not transparent to drivers. Under certain conditions, the driver needs to press harder on the brake pedal to obtain the same stopping performance that the regenerative system working in conjunction with the hydraulic brakes initially provides. Drivers are clearly upset by longer than expected stopping distances when the antilock system shuts off  the regenerative brakes.


“What I, and others have been experiencing, is certainly not “runaway acceleration” or anything to do with pressing the gas pedal,”  Robert Becker, an unhappy owner of a 2010 Prius, told TDB.

“But rather the loss of braking power or braking momentum when hitting a pothole, manhole cover, or the like. This requires the driver to press down again harder on the brakes to slow or stop the car,” Becker says.

Becker’s complaint is typical of others that ODI is tracking from owner communications on its Auto Safety Hotline. However, the existence of complaints does not mean the government will ultimately pursue the matter. The next steps would be to open up a preliminary investigation, which could be followed by an engineering analysis, which could  lead to a recall. Neither have been initiated by NHTSA thus far.

Here is another Prius driver filing: “There have been several incidents in which my car seemed to surge forward while I was in the process of braking and hit a bump, railroad tracks or pothole. Initially, I convinced myself I must have been letting up on the brake when I hit the bump, but when this same thing happened three  days ago on slippery, icy roads, I knew for 100% certain I had not let up on the brake. My car surged as I was slowly pulling up to a stop sign and gently braking. I came very close to hitting the car in front of me, had to push down on the brakes very hard, which activated the abs.”

I think what is going on is a combination of design/calibration choices and the compounding effects, forgive the pun, of the low rolling resistance tires, suspension settings and perhaps vehicle weight.

The Prius is arguably Toyota’s strongest image vehicle, dominating the hybrid segment as the best seller with more than 1 million in sales to date, and disproving other automakers’ contentions that Japanese companies only copied instead of innovating.

A Toyota spokesperson initially told TDB that he was unaware of the issue, but Toyota quickly supplied the following statement: “We are aware of the complaints filed with NHTSA. The agency has not opened an investigation. We are investigating the issue based on internet traffic, customer comments to Toyota Customer Relations, and NHTSA complaints. It is too early to speculate the final conclusion(s) of our investigation and subsequent actions.”

NHTSA would only confirm that no recall or formal investigation is underway. The ODI complaints are a matter of public record, though.

Fatal for Pedestrians?

Nonetheless, an internal NHTSA memo says: “It appears that when you hit a bump, the regenerative braking (front wheels only) cuts out, and there is a short delay until the friction braking kicks in. This results in loss of braking, which is experienced as acceleration (due to sudden end of deceleration from braking). Net impact is still a loss of braking/ increase in stopping distance. This could be fatal for pedestrians — it happens when approaching stop lights if you hit a pothole.”

Toyota is in the midst of huge recalls involving floor mats and accelerator pedals (3.8 million vehicles) and rusty Tundra frames (+100,000), among others; and it faces lawsuits alleging the withholding of evidence in safety investigations, as well as new charges of unintended acceleration, and stalling in some of  its most popular models.

Toyota’s worst year for recalls, ever

So far this year, Toyota  has said it will recall a total of 4.8 million vehicles in the United States, four times more than in any previous year. It recalled 1.1 million vehicles in 2004.

It is difficult, though, to attribute the Toyota brand sales decline in the U.S. – off  24% year-to-date, about the same as industry results — to a damaged reputation, in spite of much self-serving media and analyst commentary claiming such.

However,  the longer safety and customer satisfaction matters remain under media and government scrutiny, the more serious the potential consequences. The company announced last week the retirement of its long time group vice president of environmental and public affairs, which could be coincidental or not.

The dealership that sold Becker the car recommended that a Toyota field technician check on his complaint. The technician, according to Becker, acknowledged the condition, but stopped short of characterizing it as a safety issue.

While he initially was looking for a fix for the problem, Becker now wants a full refund of the purchase price of the vehicle, something the company is unwilling to do thus far.

“It makes me question Toyota’s commitment to customer service and safety,” Becker says.

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123 Responses to “NHTSA Tracking Braking Loss on Prius Hybrids”

  1. Len says:

    Mornin’ D; Ya want to go in business with me.I’m introducing the 2011 Darwin Sedan. No safety devices. No electronics. No nothing. Just an engine and four tires like it used to be. If you don’t drive safely you become the reason for the name!

  2. Len says:

    Paul; Thanks for the reply. My later reply was intended as a joke referring to the elimination of bad drivers through, well… Anyway, I would just like to feel that,with my background, manufactures are truly thinking about these glitches. The airline industry proves their concern of faults by requiring triple redundancy.Those circuits monitor each other and may drop the odd input or output if necessary.As you say the cost is prohibitive but falling out of the sky is a little rougher than leaving the road.
    I would like the automobile industry to think more about what is really necessary than how many bells a whistles they can add to impress the consumer.
    Last note; when you are through with your next article let me know. It sounds interesting.

  3. DGate says:

    Maybe Toyota should adopt what Ettore Bugatti was alleged to have once said to a customer when he complained about the brakes, he replied, “I make my cars to go, not to stop.”

  4. Len says:

    That’s funny but I know who’s not laughing!
    When I started driving, the only distractions were the radio and the girl next to you. Now, between 20x the traffic and everything else,it’s hard to get from point a to b without an accident. I know I’ve done some stupid things driving in my life but when I started driving as part of my job, I weighed the extra time driving per day with the averages of an accident. Even at my age that improved my driving skills. I didn’t rely on the car to do it for me.

  5. Len says:

    DGate, Bugatti was riding with a guy from California in a 2008 Prius yesterday. He supposedly got up to 90 mph, could not slow down with the brakes, called 911, a cruiser met up with him, he was spoken to or signaled to apply the emergency brake which brought him down to 50mph. He then shut the car off!!.
    I can’t say what can happen to a person in a panic situation but, there is something definitely backwards with that sequence.It also seems like a long time frame.
    Not to be cynical but, I hope this wasn’t staged in the middle of the Toyota hearings.
    Regardless, listening to all of this still makes me a little queezy because my daughter owns a Prius.

  6. DGate says:

    Len we have nothing to fear but fear itself as they say.

  7. Len says:

    Good mornin; Not much left here to post. We can just wait & see. I’m waiting for tbd’s article. Should be interesting. See you around. It’s been a pleasure talking with you. I’ll still be watching the site.

  8. Len says:

    Good Morning: If anybody is still watching this site; My daughter just had the software update installed in her 2010 Prius. She tested the system at places she experienced the braking issue in the past. So far, so good. She said there was no braking lapse or loss of deceleration.
    Obviously I am sleeping better knowing she has a little better control.
    On another note; What do you think about information released Tuesday about that guy in California??????? I wasn’t aware that the computer records that much info. Makes the whole thing look a little suspicious.

  9. DGate says:

    Glad to hear your anxieties are over.
    just goes’ to show after all the speculating of faulty brakes, regen braking anomalies, and the mysteries of the car it wasn’t hardware but down to software adjustment.
    Don’t know what to make of the last incident other than he didn’t try to shut the system down or use nuetral but chose to waste valuable time phoning and conversing with a dispatcher.

  10. Len says:

    Thanks Paul. I’m enjoying this website. I just need to learn my way around. I enjoyed the article that you recommended and the reader comments.
    I hope the auto manufactures read your website. They may get some true insight as to the average persons opinions on their products.
    We have, over the years, created a marketing strategy that puts a tremendous strain on the auto manufacturers. When you add rapid growth in technology added to “every year something new and exciting”, I think the strain may be beginning to show.
    Electronics can provide us with incredible control and performance but, from a person that understands the gremlins associated with these complex systems, I think the industry needs to be driven towards standardized systems. Controls that can take over the vehicle need to be thoroughly tested and be of high quality components and assembly. If not……….

  11. Len says:

    Back again: If anybody is still watching this site,After almost 2 months of my daughters Prius seeming to brake OK with the software update, It did it again. She got the feeling of acceleration while braking.

    I’m not sure of the braking surface. I’ll get more details later. She will be returning to the Toyota dealer obviously disappointed.

    I’ll let you know more later.

    • tdb says:

      Please DO let us know if the problem continues.
      Paul A. Eisenstein
      Publisher, TheDetroitBureau.com

  12. Len says:

    Paul; Will do. May take a few days. Thanks for the reply.

  13. [...] Htxurl AFP, and LA Times have printed stories on the safety issues relating to these two problems, and Toyota has responded (specifically to the LA Times story… Follow the links to get a full background brief on all the safety investigations).  Unfortunately for Toyota, these issues have been out there for a while now, so it’s not hard to see where the stories are coming from. [...]

  14. [...] Christmas Eve 2009, a new PriusChat community user on Yahoo pointed to the article “NHTSA Tracking Braking Loss on Prius Hybrids,” which first raised the issue of a problem with the Prius braking system. It stated there [...]


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