affiliate kare. reporter: as a recently retired mayo clinic physician, allen hoffman spent a career saving lives. but says his 2007 toyota prius nearly cost him this. he had driven his prius to a medical convention in chicago in december, was right here in this hotel parking lot, shifting into reverse, when his car took off, backwards. this was flying. i had no idea but my guess was it was 35 to 40 miles an hour. reporter: he sideswiped a car and came to a stop within feet of a busy highway. i could easily have been killed in this, almost went out into a four-lane highway at rush hour hoffman insists he slammed and held both feet on the brake as soon as the prius took off. we had practiced this. there was a little sign that my wife had put on the dashboard. we had prepare for a sudden acsellration. reporter: he felt little satisfaction in a letter he sent to toyota. this week is another apparently