Monday, March 15, 2010

Unreproducible Toyota

Last week, a California man caused a news sensation and a large traffic jam when his Prius went 90+ miles per hour on a California highway and only stopped when a police officer used his cruiser to slow the thing down. The car was tested over the weekend, and engineers were unable to reproduce the problem. Naturally, the news media is going with the claims that the man driving the car must have been lying. Gotta get those viewers!

I'm no automotive engineer, but I think we've all seen our share of problems that wound up being "unreproducible". Think of all the things it could be:

  • A race condition in software and/or hardware
  • A deadlock in software (does hardware have deadlocks?)
  • User error: the man didn't follow a procedure that could have stopped the car
  • User error: the man maliciously managed to get his break lights to turn on without actually attempting to break
  • Incorrect entry conditions: the problem only happens after the car has been driven for some period of time
  • Incorrect entry conditions: the problem only occurs when the car is at a certain speed and some other event (momentary breaking, gear shift, acceleration) also occurs
  • Incorrect entry conditions: the problem only happens when the seat is in a certain position (thus putting the angle of pedal pressure at some key spot)
I'm sure there are many many more possible explanations. Like many unreproducible issues, this one may never be definitively solved. It's an interesting exercise, though, to come up with ideas. What other possibilities can you think of?


  1. Environmental variables, such as temperature or humidity, likely differ between test runs.

  2. Matt, that's a good one. Hot things certainly work differently than cold things, and wet things differently from dry things.

  3. The driver was an enemy of the state and the CIA triggered a backdoor trap in the car s/w to try and crash the car and remove him

  4. Holy, cow, Phil. That one was an impressive leap. (And don't cut the break cables on my car... I swear we won't tell about your apparent past career as a seriously nasty, umm.... operative!).