Unintended acceleration is a complex problem. It can be caused by hardware failures, software failures, the driver and at times even passengers.
Driver panic is a real and common cause, it is challenging for the distracted, and then, surprised to brain to react quickly and properly. It is common for the driver to believe the brake is being to pressed with natural a response to press harder... on the gas pedal. A foreign object holding the gas pedal down, whether it be the floormat or loose article, is usually a driver caused incident. This is under driver control. Blaming floormat to pedal interference was the first try in the Prius case. It is probable that it happened but was not the only cause.
Hardware causes: Stuck gas pedal, sticky accelerator cable, malfunctioning throttle actuator: These can and do happen. Proper inspection and maintenance can find most, but not all of these. This was the second try in the Prius case, it was thought that the pedal case was causing the problem, many were modified but it was not proven to be the true cause.
Software causes: Poorly written PCM code has caused this problem. This was found to be the primary problem in the Prius case. The outside experts who were allowed to review it were appalled at how poorly it was written.
Is there a black box? Not specifically. Some PCM’s can and do record data, however I know of none that make this available, or even make it known. One presumes that the OEM would use it in a legal case.
Devices are available that will record 24 hours of OBDII generic data. This data includes the throttle position information for many vehicles. Starting on or about MY 2009 This data would include all of the throttle pedal and throttle actuator data.
If a vehicle does anything I do not like I plan to turn off the power and ride out the poor braking and steering that result.