This might not get your Prius to runaway but it will make your Prius pissed at you. I have not tried this and don't have the time to try it. With the brake held down and the Prius in Drive you can can press down the the accelerator and the engine will rev up. If you let go of the brake the Prius will take off. Traction control might kick in killing the power for a split second. If you just hold the the brake this is how we force charge the battery. Now lets not release the brake all the way. What will happen? Will the car take off with 50% brakes applied? If the car takes off what happens if you apply more brakes? Does the override take over and kill the engine or do you have to remove the brake 100% then reapply before the override will take over? If the override does not work unless the brake is at 0% could it be that the brake pedal needs adjusted? If the brake is setting at 5% with your foot off could this allow the car to continue to accelerate even if you mash the brake assuming that the car is at 60mph? I'm guessing you can still slow down but just not very fast. I quickly typed this up so all the details might not be there or not explained correctly.
