Pulled into driveway and put car in park. I had to close gate and lock it up and when returning to the car to turn off I was standing outside the car and it started rolling backwards. I tried to jump in the car to stop it and it was picking up speed. Driveway has a slight incline but nothing like the speed was on the car. I was in between the car door and the car seat running with the car. I am shocked I didn't get ran over. Car went across the street and hit my neighbors car and my car and well as his truck was damaged. This could have been worse and this is a huge safety feature.