Monday, March 15, 2010

Sudden Unintended Acceleration Made Simple

By The Lost Motorcyclist, March 2010

Ironically, the invention of the first motor vehicle was seen as a solution to the old problem of runaway acceleration. Back in the days of the cowboys, it was a real problem to halt a runaway team of horses. The brakes were just a stick rubbing on the wheel to stop the coach from running into the back of the horse on a downhill. One solution of course was to climb on the backs of the galloping horses, and walk your way to the front and grab the head of the lead horse, who usually had the bit between his teeth. Another way was to use a gun, but that involved killing one or more of the horses. It was better than killing all the passengers.

I noticed during the congressional hearings, that some representatives asking questions were completely unaware that runaway acceleration has always been with us. Runaway acceleration is not an exclusive Toyota problem, and reappeared soon after the horseless carriage was invented. It also does not apply only to Toyota. Just two weeks ago my sister had a case in her 2003 Honda Civic.

Even in the days of horses, runaway acceleration was an intermittent problem, and so it is often with computer controlled cars. You cannot fix a problem that is rare, intermittent, and leaves no trace, in the way you can fix a problem of outright failure like a fallen bridge. Intermittent problems are very difficult to fix, because they usually function correctly when being analysed.

Highly publicised intermittent problems tend to encourage false reports, which further hampers the investigation. Eyewitness accounts can be inaccurate and misleading.

You can't solve an intermittent problem by completely tearing apart one or more cars. From a purely scientific, logical point of view, you should sort the problems into various categories, and resist the temptation to blame evil spells or magic.

A runaway acceleration reports might fall into one of these categories:
  • Driver pressed accelerator instead of brake by mistake
  • Accelerator got caught in floor mat or under some other object left on floor (such as 500 page drivers' manual)
  • Accelerator mechanism stuck at pedal hinge
  • Stuck linkage or cable (if old style connection) to the throttle on the engine
  • stuck/iced throttle plate on the engine
  • Software logic error glitch within the engine management computer (if new fly by wire system)
  • External radio frequency interference upsets engine management computer
  • Driver accidentally set cruise control on high speed
  • Cruise control fault resulting in acceleration
  • Driver had an accident by own fault, but sincerely believes the car "ran away" on its own
  • Driver had an accident by own fault, is consciously lying, in order to avoid responsibility
  • Driver deliberately rammed something, and is using runaway acceleration as an excuse
  • The accident is blamed on runaway acceleration but is clearly something else (e.g. swerving suddenly off the road)
  • Nothing at all happened, but driver reports it to seek attention, or to hurt the car company, or to make a political statement

The various safety backups failed to prevent the accident
- There was no time to try to control the car (close quarters)
- Brakes failed to slow car at all
- Brakes initially worked, but eventually gave out and burned up
- Brake/throttle interlock failed (if so equipped)
- Shifting car to neutral was not possible/not tried
- turning engine off was not possible/ not tried.
- Car driver panicked no action was taken
- driver panicked in stressful situation, acted irrationally and made things worse

Picture: I photoshopped it to look like a runaway stagecoach with the outrider preparing to stop the horse by other means.

1 comment:

  1. This SUA controversy is not about to die. It will linger on and and on, like that chain email about cruise control in the rain that keeps turning up in my in-box again and again.

    First: an actual demonstration of braking against a fully opened throttle. Although articles have discussed the results before, seeing it in a video dramatizes the competence of the braking system, even under 'full power.' Of course, your mileage may vary but, in most cases, something similar will happen under these conditions.

    But: as one reads the reader comments on the various blogs and news sites about SUA (and there have now been millions of such postings!) one cannot but be impressed by the poor level of understanding many people seem to have about how their car functions and, further, by how adamant some of those people can be about their misconceptions being 'the truth.'

    I suppose SUA will simply join those other issues whose debate involves a disproportionate amount of misconception, emotion and propaganda.