The vehicle was operating in Autopilot mode as it approached a right turn but was in the incorrect lane. The vehicle accelerated in an apparent attempt to merge into the correct lane and initiate the turn, but it approached the turn at an unsafe speed. I pressed the brake pedal, which disengaged Autopilot as expected, but the vehicle failed to slow down or stop. I attempted to manually complete the turn, but although I turned the steering wheel, the wheels did not respond. The vehicle continued forward at speed, struck a curb on the opposite side of the road, and then collided with a parked vehicle. The impact with the parked vehicle ultimately brought the car to a stop. Multiple error messages briefly appeared on the screen during the incident before disappearing.