By on March 7, 2010

And while we are solidly in left brain mode, here the explanation of Toyota’s brake override. You can start on a steep hill, even brake with your left foot, says Toyota. Let their presser speak for itself:

The brake override feature is designed to be unobtrusive in normal driving conditions. It is designed to manage vehicle acceleration caused by interference with the accelerator pedal and is otherwise undetectable under normal driving conditions.

Using the accelerator pedal position sensors, brake light switch circuitry, and the vehicle speed sensors, this intuitive and intelligent extra measure of confidence helps ensure that vehicles can be controlled in the event that the accelerator pedal is trapped.

When the vehicle throttle is opened beyond the idle position, at speeds greater than five miles per hour and then the brakes are firmly applied for longer than one-half second, the override feature will reduce engine output to the idle position, allowing greater braking performance. If the brake pedal is then released and the engine speed does not return to normal operation, the vehicle should be brought to a stop with brake override, the engine shut off and the vehicle evaluated by a Toyota dealer.

The feature has sophisticated control logic intended to eliminate undesirable or inappropriate activation and is designed to be imperceptible. In certain driving conditions, unnecessary activation of brake override would create an inconvenient or even unsafe situation.

For example, the brake override feature does not operate if the brake pedal is depressed before the accelerator pedal. This logic allows for vehicles starting on a steep a hill to safely accelerate without rolling backwards, otherwise known as a hill start.

Toyota engineers have carefully calibrated the system control logic to prevent the system from interfering with efforts to free a vehicle by rocking it to gain traction in snow or mud. Since some drivers prefer to brake with the left foot, the system also recognizes this as an intentional action by the driver and will allow the accelerator to function normally.

[ED: Please note that only 72% of Toyota's current model line is capable of being re-flashed for this software "fix". The rest would require changes to the vehicles' hardware. Toyota has not suggested that those vehicles will receive any fix of this kind]

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14 Comments on “Toyota’s Brake Override Explained...”


  • avatar

    This system will do absoltutely nothing for the cases where people a) lie about SUA in hopes to get a monetary settlement, b) step on accelerator and do not touch brakes by mistake. And in all other cases it’s useless.

    • 0 avatar
      wmba

      But it assuages the baying dogs, and the cases where there are actual problems, which it seems to me do in fact exist in a miniscule number of cases.

    • 0 avatar
      LectroByte

      > This system will do absoltutely nothing for the cases where people… step on accelerator and do not touch brakes by mistake

      I can’t even begin to imagine something that would handle that case. What exactly did you have in mind for that one?

  • avatar
    John Horner

    That sounds like a smart bit of programming. All e-throttle cars should incorporate an algorithm of this sort.

  • avatar
    thesal

    Very smart programming…and here’s the best part:

    “the brake override feature does not operate if the brake pedal is depressed before the accelerator pedal”

    In other words, don’t read that eulogy on burnouts yet! :-)

  • avatar
    Steven02

    Sounds like good programming for the brake override.

  • avatar
    segfault

    “…only 72% of Toyota’s current model line is capable of being re-flashed for this software ‘fix.’”

    I thought all of their 2010 lineup had it.

  • avatar
    donkensler

    I just wish the software would disconnect the engines of the doofusses who drive blithely down the road with their tail lights permanently illuminated because they ride the brake pedal. But I guess it won’t, because the PR says “firmly applied”.

  • avatar
    Brian P

    If they are using the brake lamp switch status as an indication that the brake is applied, then “firmly” only requires “firm” enough to activate the brake lamps.

    Two-footed driving with the brake lamps on all the time, will trip the override. (HURRAH)

    The logic they are using sounds very similar to VW/Audi.

  • avatar
    Robert Schwartz

    Nothing is fool-proof, because fools are so ingenious.

    In December 2000, a maintenance worker at a nursing home in a small town in south-western Ohio, discovered one evening that the system that delivered oxygen to the patients of the home, was about to run out of the gas. He looked around for another cylinder of oxygen, but all he could find was cylinders painted blue. He ignored the green paint on the oxygen tank and took the blue cylinder out of storage.

    He tried to attach the blue cylinder to the oxygen system, but discovered that the coupling on the blue cylinder would not mate to the oxygen system. Nothing daunted, he removed the coupling from the old green cylinder and used it to replace the coupling on the blue cylinder. Successful at last, he connected the blue cylinder to the oxygen system, and turned it on.

    That night four patients died because the system that was supposed to deliver life giving oxygen to their weakened lungs delivered sterile nitrogen instead.

    Oxygen containers are painted green, nitrogen containers are painted blue, and they use different couplings because the two gases should never be confused.

    But, nothing is fool proof because fools are so ingenious.

    • 0 avatar
      Robert.Walter

      Idiots aside, just like the O2 v N2 mistake, it is legend that people make mistakes while trying to do the right thing. Another good case study?

      Bob Hoover, WW2 fighter jock, back-up pilot to Yeager’s Bell X-1 mission, test, demonstration and stunt-pilot supreme was nearly killed by a similar mix-up (from Wikipedia):


      Hoover Nozzle and Hoover Ring

      A perhaps-undesired recognition is the “Hoover Nozzle” used on jet-fuel pumps. The Hoover Nozzle is designed with a flattened bell shape. The Hoover Nozzle cannot be inserted in the filler neck of a plane with the “Hoover Ring” installed, thus preventing the tank from accidentally being filled with jet fuel.

      This system was given this name following an accident in which Hoover was seriously injured, when both engines on his Shrike Commander failed during takeoff. Investigators found that the plane had just been fueled by a line boy who mistook the piston-engine Shrike for a similar turboprop model, filling the tanks with jet fuel instead of avgas (aviation gasoline).[21] There was enough avgas in the fuel system to taxi to the runway and takeoff, but then the jet fuel was drawn into the engines, causing them to stop.

      Once Hoover recovered, he widely promoted the use of the new type of nozzle with the support and funding of the National Air Transportation Association, General Aviation Manufacturers Association and various other aviation groups (the nozzle is now required by Federal regulation on jet fuel pumps).

      Most of these fit/no-fit events should be caught as systems are developed, if creative-thinking engineers apply the FMEA approach. For those that are not caught, after the tragedy, and the redesigns, the case-studies should be widely disseminated.

    • 0 avatar

      +1

      I have a similar story regarding a barbeque gas tank and a kitchen stove.

  • avatar
    Kendahl

    If it works as claimed, we should still be able to heel and toe downshifts.

  • avatar
    wwide408

    Toyota and others knew they were having issues and attempted to hide it. All Car Companies should have came forward with a full disclosures of what car were dangerous. Instead of waiting for a huge media blitz and tons of public pressure. I never seen so many car companies GM – NISSAN – TOYOTA – HYUNDAI having recalls all at the same time. I had no idea my car was affected until I looked on http://www.carpedalrecall.com and found I had a bad Anti Lock control unit on my 2008 Pontiac G8 , my co workers Ford Truck had a recall also. So be careful


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