While driving at a slow speed, the traction control, brake and ABS failure lights came on. When I attempted to stop the vehicle, the brake pedal went to the floor without actuating the ABS system. I was unable to stop the vehicle using the service brakes. Since I was traveling at a low speed, I was able to slow down and come to a full stop using the parking brake. Now the vehicle is parked and undriveable. I contacted my local Toyota dealer requesting service and was told that they did not have a brake master cylinder or hydraulic brake booster in stock. I checked a second dealer and they told me that you can only get the two units together and that they were on national back order with no eta. Since purchase, I have experienced the issue that many people are reporting where the brakes release over rough road surfaces and the vehicle feels as if its accelerating. If you release and reapply the brakes it would stop. Like others, I dismissed this as a peculiar dynamic of the vehicle, however I am now convinced that there is a serious design flaw in this braking system which requires a deeper investigation. I have been in the auto industry for over 30 years and I can attest that it is not normal to have a total loss of your braking system like this, especially in a well maintained vehicle that is relatively new and have low mileage. This vehicle is now parked and available for your inspection if needed.

- Whitestone, NY, USA

Vehicle loses braking function while traveling over potholes, recessed manhole covers, and all other types of rough road surfaces. Braking function is delayed and does not return to previous power/braking strength after traversing the obstacle; this results in the need to depress the brake pedal further to re-engage enough braking function to stop the vehicle safely. Serious concern is that if the vehicle is under hard braking at the time of the event will there be enough travel left in the brake pedal to reengage the brakes enough to stop. I have experienced this regularly, one or more times per month, since I purchased the car. Up until now most occurrences have been just a minor annoyance. I researched the phenomenon on the web and many just write it off as a nuisance / minor quirk of the vehicle so I accepted that opinion and continued on enjoying the car. That is until May 21, 2013 when under hard braking (30-35mph driving speed then heavy braking to 0mph) the vehicle traveled over a recessed manhole cover and it felt like it fully lost all of its braking power and nearly sent me into the back of the vehicle stopping hard ahead of me. I had to floor the brakes before I felt any braking power return after the bump. This issue will lead to an accident if it has not already. Please keep an eye on it.

- Cottage Grove, MN, USA

Happen twice hit the brakes fairly hard on rough pavement not real rough didn't bounce just felt like I was on ice nothing there just a second or so but felt like a long time if a car would have been in front of me don't know if I could have stopped in time.

- French Lick, IN, USA

I was applying my brakes as I was going down a slight incline over a bridge that is under construction so the road is bumpy. The car acted like the gas was applied instead of the brakes. It lurched forward a little before the brakes fully engaged.

- Westminster, MD, USA

I have experienced brake issues with my 2011 Prius model since I leased the car in December 2011. When I am traveling at low speeds and I try to break going down hill and /or break over a bump in the road, the car accelerates prior to fully stopping. This has happened a total of 5 times since I leased the vehicle. It always seems to happen while I travel at lower speeds and the car lurches forward as I hit the breaks. I believe this is an issue that was experienced with 2010 models of the Prius and appears to be another acceleration issue with Toyota models in general. While there have been recalls on the 2011 Prius for deficient airbags, this is an equally concerning fault in the car that should be reviewed.

- Philadelphia, PA, USA

Car was off and parked. When I entered the vehicle to turn the car on, I held the brake and pressed the power button in order to start the car. And with my foot still on the brake, I shifted the car into reverse to pull out of the parking spot. As soon as the car was shifted into reverse, the car moved backwards with my foot fully pressed on the brake. The car felt like the brakes were not engaged. I looked down to make sure I was pressing on the brake, and the brake was completely depressed. I could even feel the hill assist threshold but the brakes were not engaging. In a panic I pressed the "P" (park) button to try to stop the vehicle. The vehicle rocked back and forth as if the vehicle was in motion when the "P" button was pressed. I got out of the vehicle to see if I was on a pothole or hill, anything to explain the move, but nothing was there, completely flat road. This has happen quite a few times when at a park and I had to contact cdsp over electronic issues over this vehicle. I am no longer going to continue with this vehicle.

- Merced, CA, USA

First incident: Was traveling approx. 68 mph on 405 freeway in los angeles (downhill into the san fernando valley). Dry conditions. Attempted to stop as cars ahead of me began to slow/halt and car lurched forward, carrying me to almost hit the car ahead of me, stopping only inches behind. Dealership could not replicate and dismissed my concerns. Multiple similar incidents all in good weather have occurred. Most recently on surface road with uneven pavement, traveling at less than 15 mph. Braking for stopped vehicles ahead, resulted in car lurching ahead.

- Diamond Bar, CA, USA

Periodically, after going over a bump at fairly low speeds, the car will accelerate. In light of the other unintended acceleration issue reported under ODI 10499911, I wonder if these two events are related -- possibly something to do with going from the motor to the battery?

- Falls Church, VA, USA

First incident: Was traveling approx. 15 mph on side street. Icy conditions. Attempted to stop at stop sign and car lurched forward, carrying me through intersection. Dealership could not replicate and thought mat might not have been fully seated. Toyota case # [xxx] 2nd and third incidences one month later (both on 2/23/2013) in fine weather conditions. 25 mph. Attempted to stop at stop sign and car lurched forward. Toyota case # [xxx] information redacted pursuant to the Freedom Of Information Act (FOIA), 5 U.S.C. 552(B)(6)..... updated 03/08/13

- Falls Church, VA, USA

I am an excellent driver. I purchased this Prius in the summer of 2011. We (my wife and young daughter) were proceeding on juanita drive N.E. in kirkland, wa. My wife and I agree that our speed was approximately 30-33 mph and that there were approximately 3+ car lengths between us and the vehicle in front of us. The weather was dry and sunny. Suddenly, a vehicle three vehicles ahead of us stopped to make a left turn, and the two vehicles behind it were able to stop. I immediately applied my brakes to the floor as soon as I observed the stopped vehicle ahead. I felt no response - no gripping of the brakes or gripping of the wheels to the road, no squealing, no skidding, no sense of the brakes slowing the vehicle in the three seconds I applied them. Due to vehicles in the opposing lane, a narrow road and no shoulder (a ditch with telephone poles on the right), I was forced to design the least harmful impact - my front right corner to the rear left corner of the vehicle in front. The impact tore open the right front of the vehicle, shattering the windshield next to my wife and causing her legs to fly up and strike the dashboard, injuring her legs in several places. Her airbag did not deploy. My 7-year-old was in her car seat in the back seat. The larger split back was behind her. The back became unhinged at impact and flipped forward, forcing my daughter's upper body forward. She sustained minor facial injuries. While it is possible that the airbag non-deployment was appropriate (I am not certain of this), there is no question that the braking was soft, squishy, non-existent, and the back seat should not have become unhinged.

- Kirkland, WA, USA

When I brake at the end of my road which has small holes or bumps, the car shoots forward very fast before it stops. This has happened numerous time. I thought at first I imagined it, or my foot slipped, but since it has happened numerous times I knew something wasn't right. So I got on web and started goggle it. And sure enough its happened to other drivers.

- Wyatt, MO, USA

I was traveling down a mountainous road and the road surface changed from gravel to asphalt. I was also braking at the same time when the brakes seem to become nonexistent and the car just lurched forward. This has happened 3 times before.

- Fairfax , VA, USA

While driving on a rough road surface and applying the brakes the car lost its brakes or the power to the brakes and surge forward. There was a feeling that the ABS had engaged than disengaged leaving the car with no brakes. Normally the brakes are very consistent, they slow and stop the car quickly and safely, however when the brakes are applied while riding on rough roads they become very inconsistent and unreliable. It feels that the brakes stop functioning, braking distance becomes longer as does the time required to stop the car. I first noticed this condition while braking on a rough road at about 30 mph. The condition now occurs not only when driving on rough roads (paved roads with potholes/pothole repairs) but also on wet/slick roads. This condition is intermittent but is occurring more frequently and at any speed, road surface and weather condition. The dealership has been unsuccessful in replicating the condition by driving the car over rough roads and applying the brakes. They tell me that unless they can experience the condition (see for themselves) they can not diagnose or repair the condition. Toyota corporate tell me they stand behind the dealership and can do nothing.

- Glen Cove, NY, USA

We purchased a 10 month old Toyota Prius on March 16nd 2012 with only 1367 miles. The prior owner who was leasing this car returned the car due to mileage inconsistency..... on Oct 5th 2012, I was driving on sunny dry day at 22mph the vehicle in front of me slowed down. I stepped on the brake to slowdown but the car did not stop. When I stepped on the brake it did not respond immediately, I applied complete pressure to the brake however the car still did not slow down enough and I hit the car in front of me. Per the report from Toyota the speed went down from 22mph to 5mph at the time of the impact. I do not agree with the Toyota report that I only stepped on the brake for 2 seconds as it was much more... before the accident the brake was much harder and less forceful pressure made the car stop after the accident the brake feels softer and more pressure is needed to make the brake work. This is an almost brand new car with 7K miles on it however I do feel safe in this car anymore after this accident and I fear for my life and public safety. What will happen I drive on a highway at 60mph and the brake will not work?? Toyota denies any technical error with the car and blames the accident on me. There are plenty of reports of similar accidents reported by consumers on this same issue here: townhall-talk.edmunds.com/direct/view/.F0db60B.

- Marlboro, MA, USA

This was not the first incident, but the most noticeable. When braking and coming to a stop, if the tires hit a pothole or any kind of hole or bump in the road, the vehicle accelerates suddenly. Today, it accelerated as I was braking and coming to stop at a red light. My back right tire went over a pothole, and the car jumped and accelerated about 10 feet. Luckily there was no car in front of me.

- Princeton, NJ, USA

On April 3 2012 we drove our 2011 Toyota Prius to a full and complete stop at a stop sign in a residential neighborhood. While we were stopped, the car surged forward approximately 5 feet before coming to a stop. My wife, who as driving looked down to check that her foot was on the brake. While staring at her foot squarely on the brake, the car surged forward again about 3 feet. The car then surged forward again about one foot before stopping. Luckily there was no crossing traffic, pedestrians or any other obstructions. No collision occurred and no one was hurt. We called Toyota care immediately and they promptly picked up the car and took it to the dealer. The dealer later called us and informed us that they had diagnosed the car and that no problem could be found. We disputed that we were unwilling to take the car back until a problem was found and they told us that they had done everything they could do and even had driven the car 10 miles with no incident. I informed them that we had driven the car nearly 10,000 miles and it happened once. Once is too many times. The dealer told us we had to take the car back. We asked for a written statement guaranteeing the safety of the car and that the issue would not occur. They said they could offer no written statement, so we refused to take the car back what followed was essentially the dealer passing the buck to Toyota corporate who basically told us that there was nothing they could do and that if we still had a problem we could go to arbitration. Toyota corporate was neither reassuring nor helpful. We are now in arbitration with Toyota. We have our arbitration hearing today. It has now been nearly two months since we have had the car, yet we are still paying the lease and insurance. We are not looking for money, we only want assurance and safety for our family.

- Los Angeles, CA, USA

When I push on the brakes and I happen to go over a bump or a pot hole, my Prius speeds up. It accelerates when I try to decelerate. I have to push harder on the brakes to really slow the car down. This problem happens when I'm driving at around 40mile/hr. I have a 2011 type III Prius. I took my car to the Toyota dealer and they claimed that they could not reproduce the problem. This is total bs because as soon as I got it back from them I could reproduce the problem on my way back home. Please advise me of what to do. [xxx] information redacted pursuant to the Freedom Of Information Act (FOIA), 5 U.S.C. 552(B)(6).

- Freshmeadows, NY, USA

Noticed brakes breaking intermittently about a week after purchase. Dismissed it because of weather and it was a new car, thought it was just different feel from my last vehicle. I don't drive often averaging 10,000 miles or less per year, so when I noticed this problem repeating, and actually near causing an accident I got concerned. Took it to the dealership today, they found nothing wrong, and on the way home experienced the same problem. The inability to stop completely presents a hazard, especially when this occurs under normal braking conditions. If the dealer can't find the problem what recourses do consumers have?

- Marietta, GA, USA