The source of the brake smell might be that the older driver pulled the emergency brake. I’ve had to do that once, thank you, mom’s lovely handmade floormat, but it’s a more common reflex in older drivers from when brakes were more likely to fail.
One day years ago the cruise control in the old lemon Subaru Legacy I used to drive decided to start switching on by itself. I’d be idling in the driveway, and the throttle would suddenly go wide open as the cruise control switched itself on and tried to bring the car up to whatever it’s last programmed speed was (50-70MPH typically). Fortunatly pressing the gas pedal still caused to to disengage, so I never hit anyone. I fixed the problem by simply disconnecting the cruise control, and not long after that replaced the car.
Re: dealing with a runaway engine on the highway.
DO NOT shift into Park. It probably won’t engage, but if it did it could result in the drive wheels locking up–sudden deceleration and likely skidding–or significant transmission damage. It would also make it easier to accidentally engage the steering lock.
Shifting into Neutral would stop the vehicle from accelerating, but would almost certainly destroy the engine in very short order. With a manual transmission, depressing the clutch will have the same effect.
I believe it’s safe to turn the key off if the car has an automatic transmission. The concern one always hears is that the steering lock might engage. That would be bad, but–most cars will not allow the key into the “lock” position unless the shifter is in Park. Try it on your car to be sure: start the engine, shift into Drive, turn the key to “off” (you can do this in your driveway). The engine will stop. Try to turn the key to “lock”–if it won’t go, there should be no concern about losing steering control.
If you have a manual transmission, or an automatic without a locking shifter, the key might be able to go “lock” regardless of what gear you’re in, but–a number of cars won’t allow the key to go to “lock” unless a release button is pushed, making it safe to turn off. If the car does not have that feature, see if the steering lock will engage before the key is withdrawn. On many cars, it won’t.
Anyway, my thought is that it’s wise to check out your car and see if it’s even possible for the steering to lock if you tried to shut it off on the highway. If not, that’s probably the best way to respond to a vehicle accelerating beyond control.
I do not know of a single vehicle that the steering wheel will lock with the ignition in the OFF position. That’s why there is a (you guessed it) LOCK position after OFF position. They may exist, but I don’t know of them. Maybe some Euro cars?
Most newer cars have rev limiters. If you dump the clutch or put it in neutral you more likely than not will “blow up” the engine.
Easiest fix and safest fix. Just shut the damn thing off. Of course, most people probably aren’t thinking rationally in a time like that. Even if by freak chance you don’t have a RPM limiter and all hell breaks loose under the hood, thats better than running into someone at 100Mph.
I agree that this is obvious when we think rationally. Nevertheless, I think that the only way I would realize I went one click too far in my panic would be when the wheel locked and then it might be too late. I think it would be too easy to simply follow instinct: repeat the motion you know best and shut it off completely. Hopefully, the very act of discussing this here has let some folks know that the possibility exists.
I thought it was kind of cool to watch my tach bouncing off of the redline as the limiter kicked in.
Should have read:
you more likely than not will not “blow up” the engine.
What a mouthful that is to say… yeesh.
I don’t know about anyone else’s, but when I shut off the engine on my car, I lose my power steering and power brakes. I’d consider this to be a bit unsafe when rocketing down the highway. 
And rev limiter or no rev limiter, I’d rather burn out the engine than kill myself and/or someone else. I stand by my recommendation of shifting to Neutral.
…when I shut off the engine on my car, I lose my power steering and power brakes. I’d consider this to be a bit unsafe when rocketing down the highway.
All cars do likewise.
Steering assist stops right away, but is a relatively minor factor at speed. Power steering is a big help at 1 mph or less, not really needed at 30mph or more (hence new variable assist systems).
Braking assist will last while there’s still vacuum in the booster reservoir, usually one or two pedal strokes worth. However, in this type of situation, one’s foot is likely already planted on the pedal with vigor, so I doubt there’d be any difference noticed.