It has been argued that pretty much all cars have brakes that are more powerful than the engine, and thus there ought to be no way for a car to truly run away.

On the other hand, it has been claimed, and seems reasonable, that in some cases, applying the brakes moderately against a car running at full throttle leads them to overheat and fail, and then there's no way to stop.

I feel like a manual transmission could be a safety device in another way - if you can pass the threshold of shifting for yourself, it may limit how impaired, by drugs/alcohol or dementia etc, you can be while still driving.