NHTSA Tracking Braking Loss on Prius Hybrids

not really. happens all the time when driving too fast on wet, icy or snowy road conditions. so what we do?? ban snow. close the roads when temps hit 32º?. that would be the same thing as blaming Toyota for selling a car without snow tires in an area where snow is likely in winter.

now, is snow tires required?? well, maybe not a good question because when i lived in Michigan they were. where i live now, its optional and i dont put snow tires on. but facts are, we still have to have some responsibility for the way we drive.

all these issues only pop up with "slight" braking force and at "low" speed. so a momentary loss of braking or control is only going to create a relatively small amount of risk mostly because the slower you go, the less likely you are to be in real danger, no matter what you are doing.

either way you look at it, one thing is very clear. we are all gonna believe what we believe and there is no doubt in my mind that after an official study on the issue is released, only half of us will accept the findings...

guess which half that will be

 

Hello All,

I've been lurking around this site since purchasing my first PRIUS back in sept 09. A prius 3 with nav and solar roof.
After reading about this braking issue for awhile now I wanted to throw in my 2 cents.
I am the systems designer for an alterative energy company that specailizes in Solar and Direct Exchange Geothermal. I find that in this market that a large percentage of people can be quick to find fault in something they do not truely understand. Many times I hear and I qoute " My old gas furnance didn't do that ". Well, simply put, this is not your old gas furnace.
In the same sense, the PRIUS is not your old car. The PRIUS is so far away and different then a traditional car it should be expected and understood that it will behave differently. Does this mean there is a safety issue? Well, I did some testing and you be the judge.
My wife and I live off a mile of unpaved road and the state of NC sometimes seems a little less then purdent about its up keep. I experence this loss of braking sensation often on this road. With that in mind I did and experiment yesterday with my new PRIUS, my wifes 2009 Corrolla with anti lock brakes and a friends 2004 Corrolla with out anti lock brakes. I tested at varius speeds and gentle to panick stops with each car and below are the results.

2004 Corrolla no ABS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking sends the car into a skid and loss of straight line stabilty.

2009 Corrolla with ABS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking engages the ABS but the stops were well controlled, straight line stabilty well maintained and felt safe and secure in all tests with this car.

2010 PRIUS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking produced the loss of braking sensation which rattles your confidence in that safe and secure feeling, however straight line stabilty was well maintained.

My conclusion is this. The braking sensation is unnerving because it is diffirent then the traditional. Things occur that you are not use too. Is this a safety issue? Again, you be the judge because the Prius in every test stopped an average of 8 to 12 feet shorter then either Corrolla. In the 04 Corrolla with out ABS had I not let off and began pumping the brakes and steer into the skids, I would have been in the weeds.

 

This is what science and engineering are all about ... doing the experiment.

Bob Wilson

 

"..as if.."

This is precisely the point. In fact there is no loss of anything. This was my key point in this whole issue. It's the 'feeling' of several new owners who are not familiar with the vehicle and its characteristics.

However the vehicle does exactly what it's supposed to do. It stops perfectly and in your hypothetical case it continues to steer perfectly.

I understand your point that the different-feeling characteristics might induce the operator to become disoriented but that goes back to the point made by many herein; this vehicle is different...intentionally different. It's not your grandfather's 20th Century auto. It's the future.

Accepting this fact and melding one's senses to the new different-feeling technology is how this progress advances. Being rigid and demanding the same feel as the prior 20th Century vehicles simply means that one may not be suited to the new advancements at this time. There are a multitude of vehicles still being made which have not advanced out of the 20th Century.

The most obvious analogy in all of this is... give a manual transmission vehicle to a driver who until then has only driven an automatic transmission, then let him or her loose on the streets with no preparation. Now that is a safety hazard. The engines revs and stalls while the vehicle leaps and lurches across every intersection it comes to. When the brakes are applied ( and the clutch not depressed ) the vehicle stalls in mid-drive in the middle of every highway.

Is the vehicle defective and a safety hazard? No one would ever state that. It's obvious that the driver has to be adaptive enough to learn the special characteristics of a manual transmission. There is no difference.

 

Well, all I can say is that for ME it's not an issue any longer. I know what to expect. For others, it may be- we will have to let time answer that one. I just hope no one has it happen and panics and switches to the gas pedal instead of the brake- it doesn't take a lawyer to hear "lawsuits" all over that situation. So, I have to err on the side of safety and still say Toyota needs to look into it and remedy it.

Why would anyone WANT this if it can be fixed without any penalty to FE? Toyota seems to want to position the car as a family car, if you look at the ads, and have it be a replacement car for anyone. If that's the case they need to make the brakes work just as effectively with the same user feel as normal brakes do. It doesn't work to say "It's a hybrid you have to put up with oddities" anymore.

What do all of you people who say it's not an issue for you have against Toyota fixing it so it won't be an issue with anyone???

 

Some of you have said it's not an issue and there have not been any accidents as the result of this issue...consider this report from the NHSTA website for a Prius 2010 (bolding by me):

Make : TOYOTAModel : PRIUSYear : 2010Manufacturer : TOYOTA MOTOR CORPORATION Crash : YesFire : NoNumber of Injuries: 1ODI ID Number : 10293583Number of Deaths: 0</SPAN>Date of Failure: November 13, 2009VIN : JTDKN3DU3A0... Component: SERVICE BRAKES, HYDRAULICSummary:
I WAS UNABLE TO SLOW DOWN GOING INTO AN INTERSECTION AT A REASONABLE RATE OF SPEED. WHILE I WAS NOT ACCELERATING, WHEN I APPLIED THE BRAKES THE CAR DID NOT SLOW DOWN AS I WOULD HAVE EXPECTED. THIS SAME BEHAVIOR HAS OCCURRED IN THE PAST SEVERAL MONTHS SINCE I'VE OWNED THE PRIUS 2010 MODEL. IT SEEMS TO SKIP FORWARD OR ACCELERATE WHILE BRAKING ON A DOWNHILL OR UNEVEN SURFACE. BY THE TIME I WAS ABLE TO STOP I THE AIRBAGS HAD GONE OFF AND I HAD HURT MY NECK AND BACK. IT IS A NEW VEHICLE THAT NOW HAS ALMOST $14,000 DAMAGE AND WON'T BE FIXED FOR A MONTH. IF ANYTHING, I'M AN OVERLY CAUTIOUS DRIVER AND WONDERING WHAT I COULD HAVE DONE TO AVOID THE ACCIDENT. *TR

 

I did some testing and you be the judge.
My wife and I live off a mile of unpaved road and the state of NC sometimes seems a little less then purdent about its up keep. I experence this loss of braking sensation often on this road. With that in mind I did and experiment yesterday with my new PRIUS, my wifes 2009 Corrolla with anti lock brakes and a friends 2004 Corrolla with out anti lock brakes. I tested at varius speeds and gentle to panick stops with each car and below are the results.

2004 Corrolla no ABS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking sends the car into a skid and loss of straight line stabilty.

2009 Corrolla with ABS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking engages the ABS but the stops were well controlled, straight line stabilty well maintained and felt safe and secure in all tests with this car.

2010 PRIUS.
Normal speed for my road and gentle braking produced a secure and safe braking feel.
High speed and panick braking produced the loss of braking sensation which rattles your confidence in that safe and secure feeling, however straight line stabilty was well maintained.

My conclusion is this. The braking sensation is unnerving because it is diffirent then the traditional. Things occur that you are not use too. Is this a safety issue? Again, you be the judge because the Prius in every test stopped an average of 8 to 12 feet shorter then either Corrolla. In the 04 Corrolla with out ABS had I not let off and began pumping the brakes and steer into the skids, I would have been in the weeds.[/QUOTE]

I just repeated the same tests again using my wifes Corrolla and my Prius.

The sensation of loss of braking, speeding up, etc is very noticable and a bit un nerving but yet I have the same results. The Prius stops shorter then my wife's 2009 Corrolla with ABS.

How can this be a safety issue when the Prius stops in less the distance then the Corrolla?

Is it truly fair to say the PRIUS should act as a conventional car?

If that were true then shouldn't a conventional car get 50 + miles to the gallon?

Shouldn't a conventional car turn it's engine off at a stop light?

I know i'm new to this forum and am not looking to upset anyone, I'm just asking folks to be a little more open minded. The Prius is different technology. Conventional cars do not function as the Prius does and Prius doesn't function as a conventional car does.

I to was worried about the braking sensation or shall I say the loss of, but I can not dispute the fact that even having this sensation the stopping distance is shorter then 2 perfectly working conventional cars.

 

To all, Forgive the repeated posts. I'm am just learning how to navagate this forum.

I just repeated the same tests again that I spoke of in my earlier post using my wifes Corrolla and my Prius.

The sensation of loss of braking, speeding up, etc is very noticable and a bit un nerving but yet I have the same results. The Prius stops shorter then my wife's 2009 Corrolla with ABS.

How can this be a safety issue when the Prius stops in less the distance then the Corrolla?

Is it truly fair to say the PRIUS should act as a conventional car?

If that were true then shouldn't a conventional car get 50 + miles to the gallon?

Shouldn't a conventional car turn it's engine off at a stop light?

I know i'm new to this forum and am not looking to upset anyone, I'm just asking folks to be a little more open minded. The Prius is different technology. Conventional cars do not function as the Prius does and Prius doesn't function as a conventional car does.

I to was worried about the braking sensation or shall I say the loss of, but I can not dispute the fact that even having this sensation the stopping distance is shorter then 2 perfectly working conventional cars.

 

It just occurred to me that this loss-of-braking sensation is very similar to the sinking feeling you get in an airplane when the pilot reduces the flaps and the rate of climb is reduced. The plane is still climbing, but it feels like it is sinking because the rate of climb is less. In just the same way, the Prius may feel like it is accelerating, but it is actually just decelerating more slowly for a fraction of a second. As long as the actual braking distance is within acceptable limits (and it seems to be) then this is not a safety issue. It is just a sensation.

 

ok. just got back from Costco... and did hit a spot on the roundabout that worked well for brake loss but was not ready for it, so just had a start, so i circled the block, hit it again and waited for the slip, as soon as it started, i slammed the brakes on, came to a dead stop and now everything in the car is piled up against the doors on the right side.

what i did was hit roundabout at about 30 mph slowing as i hit the curve to around 15-20 mph. but like i said when i hit the brakes hard at the start of the slip, i pretty much came to a stop immediately. no skid, no nothing.

will never do that again!!... damn brakes work too good

 

I have to say that the brakes on my 2005 Prius are much better than on my 2003 Camry or 1995 Tercel. In fact, they are the best brakes I have every experienced on any car. They lasted over 100,000 miles before I replaced the pads and rotors.

 

Eoin,
I agree that it may just be a sensation...however, as a passenger in a plane you are not in control of said plane. If you were the pilot and you experienced this sensation you might try to compensate in a way that might make conditions worse if it was the first time you experienced said sensation and you were not aware of the effect.

However, in looking at some NHTSA reports, it appears at least one person reported an accident ($14,000 in damages) as the fault of the brakes...and mentions the effect is produced by UNEVEN SURFACES. It may be a sensation for some of us, and a safety risk for others.

 

I can see the Prius haters really going after us soon if we take this grassroots testing too far...

"THOSE DARN PRIUS DRIVERS CAN'T DRIVE- I ALWAYS SEE THEM DRIVING RIGHT INTO POTHOLES AND THEN SLAMMING ON THEIR BRAKES!"

 

Bighouse,

Even though that Accident was reported by one person, the details are never clear and concise. It could have been Operator error involved as well, so many other variables.

I only detected this once and it was on a uneven pavement from a overpass to the existing road surface. I can now duplicate it, at this same location if I hit it right.

But now, when pushing harder on the brake I won't experience it. So I suspect I was applying pressure to lightly, since if I do it again at the same location with a light brake application, It will repeat itself.

But I wanted to add this, I could see the uneven gap in the road beforehand. So now I try to avoid braking right on them if I can...It's sort of a learning curve. If I see I am going to be stopping where one of those "sunken Manholes" are, I just brake slightly different.

It will be interesting if they find an issue but as of this time, I am doubtful. But certainly following the threads.....to see.

 

The braking system on this car is so strong. The VSC is supposed to help with those unexpected surface changes. Obviously, from Dave's CostCo trip, you can still slam on your brakes and have them work.
As cars advance people need to realize that reading manuals and really paying attention to the various systems that your vehicle comes with is very important.
This forum is great support and provides so many answers. I would really like to thank all of you who go out there and shift into neutral while driving, slam on your brakes and other trials.

 

i was trying to find the exact racing quote... but basically, the saying goes "brake before the turn, and accelerate out, and you'll be fine. if you brake into the turn... you're going to die."

 

I am all for Toyota to look into it. It may not need a "fix" but education to the new hybrid owners. It may turn out that the feel needs to be consistent across all situations. However, I am against making the real issue (sensational) to something that it is not ("Braking Loss" issue as titled).

I see this as a feature by the fact that the brakes give a feedback to feel the connection to the road. Prius has been bashed to drive like an appliance (by uneducated gear heads) for not giving enough feedback. Now it is being bashed for giving too much feedback.

 

Perhaps if that driver were in a Corolla, the damage may be worse. The other owner tests show the Prius stops with shorter distance than a non-hybrid.

 

I'm certianly for toyota looking into this or any third party for that matter. I agree as well that my terminology in stating the loss of braking to be a sensation is incorrect. I will agree that the sensation of no braking is because indeed, for that instance, there is no braking.

What I am saying is that I believe this to be a byproduct of design. The Prius has many systems that work in various combinations. Re-gen braking, standard braking, VSC, ABS,etc. In the right conditons the transition from re-gen to standard brakes, the on set of VSC, ABS or what ever, may not be as seamless as we would like.

When braking re-gen is the first system to engage. When you hit loose, broken or uneven pavement and a tire loses contact with the road it will decelerate faster then the tire in contact. At this point the VSC stops re-gen braking which allows both front wheels to equalize there speed. This is where we notice the loss of braking feel. The sensation if you will, because in fact, at that moment in time, there is no braking. Once the wheel speeds equalizes then the standard brakes engage. If ABS engages (which only works with the standard brakes) we don't notice the braking loss because ABS only releases the brake on the wheel that decelerates the fastest. The purpose behind all this is to maintian steering control which is normally lost in a skid.

These transitions have to exist for all these systems to function together. For me, I am satisfied that a safety issue is not present because although it may feel scary, the prius stops quick and stable no matter how hard I try to make it do other wise.

I'm sure there are other cars out there that stop faster them the Prius but I only have the Corolla at my disposal to compare it to. And with that I must say that my wifes Corolla with ABS and the Prius sure made me feel much safer then the 04 Corolla with out ABS did.

The issue for me is can Toyota make these transitions less noticeable. If we could not feel this happen then we would not be debating the issue.