Comment Re:Almost Always User Error (Score 1) 930
It really is.
You can have more than one source supply power to a light bulb. In the case of the brakes, it's a physical switch. In the case of the hazard lights, it's a physical switch linked to a relay. The ABS only comes into play when the computer detects a wheel lock-up, and it does it by reducing the braking pressure, in pulses. If there is no computer response, then the brakes will apply normally.
My car is ~6 months old (and Japanese). It has a physical switch for the brake lights. As did the 10+ cars before that.
Braking *has* to be a mechanical system. If the computer that controls your fly-by-wire goes up the shitter, then you would be left with a car than cannot be stopped, unless you're lucky enough to be going up a hill. Nobody would sign off on such a thing. There is a chance the brake servo may not work, but it's very unlikely, as there have been brake servos long before there were ECUs, and I can't think of a good reason to try to make a brake servo electronic.
If this womans brake lights came on at all, then all the time they did not come on, she was NOT braking.
What happened with your father in law is likely different. I had a Peugeot that would also rev itself, but only at idle. This was most likely due to a faulty sensor, as it would be alright after a service, and other people I know with similar age peugeots had the same thing. A solution for your father in law would be to take it out of gear and apply the handbrake when he's stopped, like his instructor probably mentioned.