After the Toyota recall over loose floor mats interfering with gas pedals, Consumer Reports tested stuck throttle scenarios with a Toyota Venza, Chevrolet HHR, Volkswagen Jetta Wagon, and Mercedes-Benz E350. The nature of the test was simple, but probably a bit harrowing: the drivers floored the gas pedal until the cars reaches 60 mph, then, keeping the gas depressed, pushed down the brake pedal to see if the car would stop.
The test wasn't quite fair, as both German cars had a tech trick, called Smart Throttle, for just such a situation. When the brakes are applied, the throttle lifts, no matter what's happening with the gas pedal. According to the Consumer Reports blog post, both cars easily came to a stop, and the engines idled even with the gas pedal floored.
With the Toyota and the Chevrolet, the drivers performed this test at 20 mph the first time because the cars did not have the Smart Throttle technology. Both cars downshifted quickly when put through this test, and the drivers had to struggle to keep pressure on the brakes, fighting engine torque. But they were able to bring the cars to a stop. Repeating the test on these cars by running up to the full 60 mph, the drivers were able to slow to about 10 mph, but brake fade kept them from coming to a complete stop.
Consumer Reports concludes, as Toyota said in its advisory, that the best thing to do if your throttle is stuck is put the car in neutral. The engine will continue to run at horrendous speeds, but the rev limiter will keep it from burning up over redline. When the car is safely stopped on the side of the road, you can turn it all the way off.