general problems of the 2012 Toyota Prius - part 2

A groaning noise at all temperatures so far. It begins and then goes away after I drive for a block. It is very loud and it can be heard by others around me. It is embarrassing and doesn't sound like it is healthy for the longevity of the vehicle.

1. When vehicle transitioned from battery to motor, significant impact resulted 2. Brake pedal traveled to floor, dash warning light came on [vehicle towed] 3. Attempting to leave dealer's lot, brake pedal traveled to floor. Technician witnessed.

My car has an issue I first noticed soon after I bought it, and that now happens at least twice a week. The date I've entered is the approximate first date I noticed the problem occur. I describe below a more recent instance of the same behavior, the time when it felt the least safe. /// the recurring behavior is that while decelerating with my foot on the brake pedal, if the car goes over an obstruction like a rock, a rough patch of road, or a pothole, it sometimes lurches forward before resuming deceleration. The sensation is of accelerating, but even if it's only that the car momentarily stops decelerating it's disconcerting and in a few instances has gotten me close to an accident. /// the time it came closest to causing an accident was on 3/21/13, when I feared the car was going to roll into a crosswalk as people crossed. With my foot on the brake, coming to a stop at a stop sign, we went over uneven pavement and the car lurched forward while only a few feet from the crosswalk. Several people waited close to the edge of the sidewalk at a bus stop. One of them seemed ready to step out to cross the street, and I braced for the worst. /// ultimately I stopped a few feet before the crosswalk, but the situation felt completely unsafe since it involved losing stopping power while coming to a stop sign with pedestrians present.