Extreme Emergency Braking?

Apply the park brake, put it in "Brake Mode", try to move to the right shoulder and pray. While doing all this remember the emergency flashers.

 

My ideas:

(1) Put your full body weight into the brake pedal. By full weight, I mean at least 112 pounds (500 newtons, for the metrically inclined). Don't assume the brakes have failed when the pedal feels dead and (almost) on the floor at 50 pounds.

Federal passenger car regulations allow for various failures of power assist and electric brake systems, reverting to old fashioned manual brakes. In these cases, the remaining manually powered hydraulic system is required to meet certain stopping standards at a pedal pressure of 112 pounds. But more pedal force is always better.

(2) If moving at any significant speed in D gear, shift to B to get some engine braking.

(3) (already mentioned) Apply the parking brake.

(4) If moving very slowly, shift into Park. If the car is below a threshold speed, it will go into Park and stop with a jolt. Above that threshold, it will refuse and go into Neutral instead, with a double beep warning.

(5) Look for soft inanimate targets and gentle run-out zones. Long sideswipes count as soft. If you must hit something, the car's occupant protection is stronger for square head-on hits than for offset or sideways hits or rollovers.

There ought to be a few more ideas to put in here ...

 

Although the Prius doesn't have a proper E-brake, you can use the P brake in an emergency....you just have to do so a lot more carefully since (IIRC....I really haven't looked in this car!) this is a ratcheted cable to your rear brakes only.
Activated with panic inspired, adrenaline boosted ferocity at highway speeds, it will probably turn your G3 into somebody's source for "recycled, used auto parts."
If you're unluckier still.....and depending on your state's policy for donor organs - your car parts may not be the only things that get recycled.

However (comma!) hydraulic assisted brakes - even regenerative ones, have been around for a long time. Sniveling, bottom-feeding, bed wetting attorneys have been around even longer (like, since before Bill Shakespeare.)
This means that REAL brake failures are somewhat uncommon.
Like.....REALLY REALLY rare.
Usually it's what we call a dead short between the seat and the steering wheel....or a panic stop that resulted in an "unintended acceleration."
(see also: geriatrically, chemically, or intellectually impaired driving. )

It's kinda like comets meteors and/or asteroids.
OK to worry about if you're into things like that but I wouldn’t lie awake at night staring at the ceiling over it.

YMMV.


Reader's Digest Version: Almost always...it's the driver that fails, not the brakes.

 

If the brake pedal feels soft, goes to the floor and the car accelerates, your foot is on the throttle.....it has happened.

 

Loosing brakes happens quit often on the race track. Remember, brake fluid is extremely hygroscopic, so the minute it is open from the canister it is absorbing moisture from the atomosphere, same goes for the fluids that's in your reservoir. That's why it is always recommended that you flush out your fluids at least once a year. Well, for the Prius maybe once every 2 years. The reason is because moisture lowers the boiling point of the brake fluid, and when brake fluid boils it turns to gas, and we all know gas is compressible, so the pedal force is taken up by the gas and pedal goes to the floor and you loose all braking power.

Solution. Pump your brakes, although we were taught on the newer cars with ABS brakes not to pump the brakes. But if you your pedal goes to the floor and the car is not stopping. Pump it hard and fast.

When most likely will you experience this? On a long steep down grade where you have to constantly use your brakes. It happens more often than you think.

How to prevent this? Flush your brake system once a year.

 

Pumping the brake also helps detect pedal misapplication, i.e. pressing the gas instead of the brake.

This is a case of picking your poison. Pumping the brake is the right response to certain failures, and the wrong response to other failures.

On long steep downhills, drivers should also use engine braking -- B-mode in a Prius, downshifting in traditional cars -- to keep the brakes from overheating.

 

And you think how many actually read the manual? LOL!

 

This thread has degenerated into a "the brakes won't fail" thread. Back to the original question. IF the hydraulic brakes completely fail use the parking brake and "B". The parking brake is not powerful and neither is "B" for stopping but it would be all you would have. DO NOT try to use "P" or "R". The car will go to "N" and you'll be worse off.

And for those who still say Prius brakes can't fail, don't be silly, I refer you to Murphy's laws. Anything is -possible- and it's good that the OP is wondering "what if". For example, you hit -something- on the road and it severs the main hydraulic line and you loose all brake fluid. Yup, very unlikely, but still possible.

 

Easing into a guard rail or concrete lane divider will only destroy the car, not the occupants. I have seen a truck use a runaway truck lane, it moves a lot of gravel!

 

???

This depends on the situation. And I'm responding to the more general field of brake failure, which includes many other faults that initially masquerade as total hydraulic failure.

In a pilot-induced Sudden Unintended Acceleration, going to "N" is part of a proper response. Been there, done that in a previous non-hybrid. This is far more common than true brake failure.

This forum has received sporadic reports of Prii brakes not working immediately after power-up, possibly in other situations. So far these reports lack sufficient detail and critical mass. At least one reader rolled into a collision. At least one more put his full weight into the pedal, as I suggested above, and it saved the situation. Some have obviously put only power-assist levels of force on the brake pedal, not the heavy force needed for manual braking, while others were indeterminate.

Some, including me on two occasions on my first Prius, reflexively shut down and rebooted the car, clearing the fault. In my cases, the car was still in a parking space and rolling very slowly, so "P" should have worked. Full force on the pedal also should have worked, but other actions cleared the fault before I could think to try these actions.

Yes, the underlying hydraulic brakes can fail. But of the problems that initially feel like hydraulic failure, the vast vast majority are something else with an easier immediate solution. So don't assume the brakes have failed without going through the list above.

 

Pretty tough to lose all braking in a Prius. Are we talking about losing regen braking, plus both circuits of the hydraulic brake system failing at the same time? You'd have to resort to shifting to B, applying the emergency brake incrementally, signaling (if you turn the emergency blinkers on right away you lose the ability to signal direction change) and then head to the breakdown lane as safely as possible, if that option is possible.

Would definitely avoid pressing the emergency brake pedal too hard, to keep the rear brakes from locking up. All this is obviously dependent on traffic situation, speed and escape routes available to the driver. Might want to try slowing with B and emergency brake someplace safe to see how your Prius reacts.

 

On that topic, Runaway-Truck Ramps Explained - Feature - Car and Driver is insightful.

I have seen of video of them properly working in a documentary.

 

But I heard that them hybrids generate a powerful magnetic field, pulls meteors down right on top of them, automatically kills everyone in the car. Why the Tesla people have it so bad they've come out with a titanium meteor shield that goes on the middle of the car somewhere. I know it's true because I read it in that new CNW Marketing Research report...

 

Shields up!

 

If you lose braking in one of these....make sure you have a great attorney because if you live you'll be rich

 

1( Dont panic
2(Apply brakes
2a(If fail dont panic but continue applying bakes (regen is assisting in slowing down)
3(place shifter in B
4(Slow apply parking brakes you dont want to lock up your rear wheels and take you on a spin
5(pull over on the side
5a(if your still going to fast and you cant slow down turn your car into a barrier to slow down