Toyota Revisiting Electronics Throttle Control

The Wall Street Journal reports that a preliminary study carried out by Exponent showed that “”Exponent had been unable to cause sudden acceleration by making electrical disturbances to Toyota vehicles’ electronics systems”.   It is not clear from this report whether the disturbances were generated from external sources or not.   I tend to think that external disturbances are unlikely to cause and leave a throttle stuck to create sudden and sustained unintended acceleration (SSUA).   (The Ford situation described in a previous blog posting relates to internal disturbances to which the Ford braking system reacts by switching from regenerative braking to hydraulic braking – a software glitch that Ford has promised to fix).

According to an AP article, a spokesperson said that Toyota “does not think there are any electronics problems with its vehicles, but promised to look into it again”.    Another article from Reuters notes that, according to the Yomiuri paper from Japan, “Toyota … aims to demonstrate that there are no problems with the systems with help from external experts”.

I like the fact that this quote uses the word “demonstrate” and not “prove”.   How would one “prove” that such systems have no problems?      One must point out that designers of complex systems always aim to bring failure rates to an acceptably low level and not to zero.   While some members of the public (or the media) may react with panic at the notion of non-zero failure rates where lives may be at stake, that is how all systems in practice behave.  One can imagine a scenario where basic assumptions do not hold.  As long as the failure rate is below a very low threshold, the benefits can outweigh the risks.  One also puts in multiple levels of backups, so that damage if it occurs is dramatically reduced.


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