Quote:
Originally Posted by iTsLiKeAnEgG
I believe I've seen demonstrations showing that pressing the brake pedal does override the throttle and stop the car fairly quickly. In fact I've seen video of more powerful cars than the V6 Camry being brought to a halt from 60-80 mph with just the brakes even though the engine was at full throttle.
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The actual mechanics of this were gone over in the original thread on this topic. If we peg the accelerator on the car, the engine goes to WOT and while in that condition there is no vacuum being generated to provide braking assist. The brake system itself will maintain enough pressure for one or two applications before the mechanical effort to push the brakes is too great to bring the car to a stop under WOT by the force of you pushing on the pedal alone. Basically since power assist brakes were created, the actual pedals have been redesigned and do not provide the mechanical leverage they used to.
So, you are correct that in any car it can be done, but you really only have a couple tries to do it. In the case of unintended acceleration, most people would jab the brakes repeatedly or try them a couple times and at that point they have lost all vacuum assist (most likely what happened with the troopers car in CA). What you would need to do is realize what is happening and have the sense to stand on the brakes and bring the car to a complete stop on the first or second try at the brakes.
What Toyota has added moving forward and has been a feature on almost all other brands electronic throttles is a safety switch that overrides throttle input when the brake pedal is pressed. Basically, even if the pedal was stuck at WOT, by hitting the brakes, it would send an override signal to the actual throttle body to close. This in turn allows vacuum to replenish and would bring the car to idle while you are braking. Such a system would have prevented what happened to the CA trooper.
So, take the troopers example.
1. Pedal gets stuck under stacked floormats causing the car to go to WOT and begin accelerating.
2. Most peoples first reaction would be to hit the brake pedal, which would begin to slow the car (throttle blade is still at WOT, so no vacuum) and then let off.
3. Car lunges forward again, so you go back to the brakes in an effort to control it.
At that point, you either need to stay on the brakes and bring the car to a complete stop and hold the brakes there until you can get the car into neutral or get it turned off.
4. The trooper didn't come to a complete stop, so now the car is accelerating again, but we have lost our vacuum assist. This scenario seems to be backed up by the 911 tape and witness accounts that stated the front brakes were pretty much on fire. There was enough force applied to push the pads against the rotors, but not enough to overcome the force of the vehicle moving forward.
At this point, the only option is to turn the car off or get it into neutral.
5. The 911 tape provided evidence that the trooper tried to turn the car off, but it was a push button system. He didn't know that you had to press and hold the button for several seconds and then the car would shut off. The keyfob couldn't be removed do to a feature of the Toyota system that didn't allow the fob to be removed while the car was in gear.
6. For some unknown reason the trooper could not get the car into neutral. The model he was driving had a J-gate style shifter. This point is the one no one knows for sure why he couldn't get the car in neutral and created some speculation that it might be a design feature to prevent the car from going into neutral under high revs.
What Toyota has done (which many others have done for awhile) is address a couple specific points:
Number 1 was addressed by the recall and subsequent warnings.
Number 2 and 3 are covered by the brake override on all new cars, that would have closed the throttle blade and allowed vacuum to build and made the motor go to idle and the car to stop.
Number 5 was addressed by copying the "panic" shut off feature that many other brands use. Basically, you either push and hold the button for a period of time and the car shuts off, or you repeatedely press the button 3 times within a certain window of time and the car shuts off. They also changed it so that removing the fob is possible and the car will shut off.
If our trooper had been driving say an Audi or Cadillac, he and his family would still be alive.
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