You asked for it, you got it. Toyota!

I think that's how the ad line went. When? maybe 25 years ago.

Well, it seems to apply now. Sudden acceleration. Mention a problem with a car, any problem with any car, and people will start crawling out of the wood-work with the complaint. Why? It's a numbers game. There were more than 100,000 pri-i(?) sold in the US in 2005-9. With that many people driving them around, any tiny problem that is reported is going to be "substantiated" by others. Those of us old enough to remember the Audi 5000 found the high correlation between those Audi's with sudden acceleration and those sold to 85 year-old ladies inexplicable (studies mostly concluded it was driver error--see a recent article here in Wired).

The latest, after the brake-related Prius recall, is the claim of sudden acceleration. A guy in California managed to call 911 while it was happening--pretty amazing, huh? Unless, of course, you made it all up. Here's what the current thoughts about it are (from wikipedia):
"On March 8, 2010, a 2008 Prius allegedly uncontrollably accelerated to 94 miles per hour on a California Highway (US), and the Prius had to be stopped with the verbal assistance of the California Highway Patrol as news cameras watched ^[86]. Subsequent to the event, media investigations uncovered suspicious information about the alleged runaway Prius driver, 61-year old James Sikes, including false police reports, suspect insurance claims, theft and fraud allegations, television aspirations, and bankruptcy.^[87][88] Sikes was found to be US$19,000 behind in his Prius car payments and had $US700,000 in accumulated debt.^[87] Sikes stated he wanted a new car as compensation for the incident.^[87][89] Analyses by Edmunds.com and Forbes found Sikes' acceleration claims and fears of shifting to neutral implausible, with Edmunds concluding that "in other words, this is BS",^[90] and Forbes comparing it to the balloon boy hoax.<sup>[88]"

Notwithstanding the apparent CA tale above, the reality is that the rare problem is a tough nut to crack statistically. Suppose there is an issue in 1 in 10,000 Prius' and that this issue only crops up on one in 10,000 rides on those cars. Thus, it's a 1 in 100 million car rides in Prius. Even among those, it may be a very short-lived problem and not cause any injury or accident. Such a rare problem might be drowned out by other driver error problems, such as accidently hitting the gas instead of the break, perceiving that the car is accelarating when it is not, hitting both the gas and the break simultaneously in an attempt to hit the break. Each of these things can be exceedingly rare (1 in a million) and still be 100 times as common as the real problem.

There are other ways to go about teasing out rare events. In the lab, a machine could possibly simulate conditions that were occurring when the supposed sudden acceleration took place and see if it is repeatable. Yet these conditions are hard to figure out, as they are determined with the imperfect information of the person reporting the incident. As might be the case with the recent report, that person could be lying, but even if not, they are likely shooken up enough that they cannot remember the exact conditions very well. Consider airline crashes, where we often have very objective information (the black box), but it is still very difficult to figure out what happened and why.

One thing seems certain to be true: we won't know whether or not Prius cars are at fault for a long time to come, and far fewer of them will be bought in the next couple years.</sup>